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EGL 1.5 Specification — EGL 1.5 Specification

Khronos Group · Khronos Group

Khronos · Standards · License: Open Access

khronos, specification, standard, egl, 1.5

Khronos Native Platform Graphics Interface (EGL Version 1.5 - August 27, 2014) Editor: Jon Leech

2 Copyright (c) 2002-2014 The Khronos Group Inc. All Rights Reserved. This specification is protected by copyright laws and contains material proprietary to the Khronos Group, Inc. It or any components may not be reproduced, republished, distributed, transmitted, displayed, broadcast or otherwise exploited in any manner without the express prior written permission of Khronos Group. You may use this specification for implementing the functionality therein, without altering or removing any trademark, copyright or other notice from the specification, but the receipt or possession of this specification does not convey any rights to reproduce, disclose, or distribute its contents, or to manufacture, use, or sell anything that it may describe, in whole or in part. Khronos Group grants express permission to any current Promoter, Contributor or Adopter member of Khronos to copy and redistribute UNMODIFIED versions of this specification in any fashion, provided that NO CHARGE is made for the specification and the latest available update of the specification for any version of the API is used whenever possible. Such distributed specification may be reformatted AS LONG AS the contents of the specification are not changed in any way. The specification may be incorporated into a product that is sold as long as such product includes significant independent work developed by the seller. A link to the current version of this specification on the Khronos Group web-site should be included whenever possible with specification distributions. Khronos Group makes no, and expressly disclaims any, representations or warranties, express or implied, regarding this specification, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose or non-infringement of any intellectual property. Khronos Group makes no, and expressly disclaims any, warranties, express or implied, regarding the correctness, accuracy, completeness, timeliness, and reliability of the specification. Under no circumstances will the Khronos Group, or any of its Promoters, Contributors or Members or their respective partners, officers, directors, employees, agents or representatives be liable for any damages, whether direct, indirect, special or consequential damages for lost revenues, lost profits, or otherwise, arising from or in connection with these materials. This document is a derivative work of ”OpenGL R Graphics with the X Window System (Version 1.4)”. Silicon Graphics, Inc. owns, and reserves all rights in, the latter document. Khronos is a trademark of The Khronos Group Inc. OpenGL is a registered trademark, and OpenGL ES is a trademark, of Silicon Graphics, Inc. EGL 1.5 - August 27, 2014

Contents 1

Overview

EGL Operation 2.1 Native Platforms and Rendering APIs . . . . . . . . . . . . . . . 2.1.1 EGL Types . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Displays . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Rendering Contexts and Drawing Surfaces . . . . . . . . . . . . . 2.2.1 Using Rendering Contexts . . . . . . . . . . . . . . . . . 2.2.2 Rendering Models . . . . . . . . . . . . . . . . . . . . . 2.2.3 Interaction With Native Rendering . . . . . . . . . . . . . 2.3 Direct Rendering and Address Spaces . . . . . . . . . . . . . . . 2.4 Shared State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 OpenGL and OpenGL ES Texture Objects . . . . . . . . . 2.4.2 OpenGL and OpenGL ES Buffer Objects . . . . . . . . . 2.5 EGLImages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Multiple Threads . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Power Management . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 2 2 3 4 5 5 7 7 8 8 8 9 9 10 10

EGL Functions and Errors 3.1 Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Generic Errors Are Not Described Repeatedly . . . . . . . 3.1.2 Parameter Validation . . . . . . . . . . . . . . . . . . . . 3.2 Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 EGL Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Configuration Management . . . . . . . . . . . . . . . . . . . . . 3.4.1 Querying Configurations . . . . . . . . . . . . . . . . . . 3.4.2 Lifetime of Configurations . . . . . . . . . . . . . . . . . 3.4.3 Querying Configuration Attributes . . . . . . . . . . . . .

12 12 14 14 15 18 19 26 31 31

CONTENTS

3.5

Rendering Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Creating On-Screen Rendering Surfaces . . . . . . . . . . 3.5.2 Creating Off-Screen Rendering Surfaces . . . . . . . . . . 3.5.3 Binding Off-Screen Rendering Surfaces To Client Buffers 3.5.4 Creating Native Pixmap Rendering Surfaces . . . . . . . . 3.5.5 Destroying Rendering Surfaces . . . . . . . . . . . . . . 3.5.6 Surface Attributes . . . . . . . . . . . . . . . . . . . . . 3.6 Rendering to Textures . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Binding a Surface to a OpenGL ES Texture . . . . . . . . 3.6.2 Releasing a Surface from an OpenGL ES Texture . . . . . 3.6.3 Implementation Caveats . . . . . . . . . . . . . . . . . . 3.7 Rendering Contexts . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1 Creating Rendering Contexts . . . . . . . . . . . . . . . . 3.7.2 Destroying Rendering Contexts . . . . . . . . . . . . . . 3.7.3 Binding Contexts and Drawables . . . . . . . . . . . . . . 3.7.4 Context Queries . . . . . . . . . . . . . . . . . . . . . . 3.8 Synchronization Primitives . . . . . . . . . . . . . . . . . . . . . 3.8.1 Sync Objects . . . . . . . . . . . . . . . . . . . . . . . . 3.9 EGLImage Specification and Management . . . . . . . . . . . . . 3.9.1 Lifetime and Usage of EGLImages . . . . . . . . . . . . 3.10 Posting the Color Buffer . . . . . . . . . . . . . . . . . . . . . . 3.10.1 Posting to a Window . . . . . . . . . . . . . . . . . . . . 3.10.2 Copying to a Native Pixmap . . . . . . . . . . . . . . . . 3.10.3 Posting Semantics . . . . . . . . . . . . . . . . . . . . . 3.10.4 Posting Errors . . . . . . . . . . . . . . . . . . . . . . . 3.11 Obtaining Function Pointers . . . . . . . . . . . . . . . . . . . . 3.12 Releasing Thread State . . . . . . . . . . . . . . . . . . . . . . .

31 31 35 37 40 41 42 46 46 48 49 49 51 57 58 61 64 65 72 77 79 79 80 80 81 82 83

Extending EGL

EGL Versions, Header Files, and Enumerants 5.1 Header Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Compile-Time Version Detection . . . . . . . . . . . . . . . . . . 5.3 Enumerant Values and Header Portability . . . . . . . . . . . . .

86 86 87 87

Glossary

A Version 1.0 A.1 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . .

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92 92

CONTENTS

iii

B Version 1.1 B.1 Revision 1.1.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . B.2 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . .

93 93 93

C Version 1.2 C.1 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . .

95 95

D Version 1.3 D.1 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . .

96 96

E Version 1.4 98 E.1 Updates to EGL 1.4 . . . . . . . . . . . . . . . . . . . . . . . . . 99 E.2 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 102 F Version 1.5 104 F.1 Change Log for Released Specifications . . . . . . . . . . . . . . 105 F.2 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 107

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List of Tables 3.1 EGLConfig attributes. . . . . . . . . . . . . . . . . . . . . . . . 3.2 Types of surfaces supported by an EGLConfig . . . . . . . . . . 3.3 Types of client APIs supported by an EGLConfig . . . . . . . . 3.4 Default values and match criteria for EGLConfig attributes. . . . 3.5 Queryable surface attributes and types. . . . . . . . . . . . . . . . 3.6 Size of texture components . . . . . . . . . . . . . . . . . . . . . 3.7 Fence sync attributes and initial values. . . . . . . . . . . . . . . 3.8 OpenCL event sync attributes and initial values. . . . . . . . . . . 3.9 Attributes accepted by eglGetSyncAttrib. . . . . . . . . . . . . . 3.10 Legal values for eglCreateImage target parameter. . . . . . . . . 3.11 Legal attributes for eglCreateImage attrib list parameter. . . . . .

20 23 24 29 44 47 67 68 71 74 75

D.1 Renamed tokens . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 1

Overview This document describes EGL, an interface between rendering APIs such as OpenCL, OpenGL, OpenGL ES or OpenVG (referred to collectively as client APIs) and one or more underlying platforms (typically window systems such as X11). It refers to concepts discussed in the specifications for these client APIs, and should be read together with those specifications. EGL uses OpenGL ES conventions for naming entry points and macros. EGL provides mechanisms for creating rendering surfaces onto which client APIs can draw, creating graphics contexts for client APIs, and synchronizing drawing by client APIs as well as platform rendering APIs. EGL does not explicitly support remote or indirect rendering, unlike the similar GLX API.

Chapter 2

EGL Operation 2.1

Native Platforms and Rendering APIs

EGL is intended to be implementable on multiple operating systems (such as Android, Unix, and Windows) and platforms1 (including window systems such as X11 and Microsoft Windows, and platforms supporting rendering without a display, such as GBM). Implementations may also choose to allow rendering into specific types of EGL surfaces via native rendering APIs specific to a platform, such as Xlib or GDI. Native rendering is described in more detail in section 2.2.3. To the extent possible, EGL itself is independent of definitions and concepts specific to any platform or rendering API. However, there are a few places where native concepts must be mapped into EGL-specific concepts, including the definition of the display on which graphics are drawn, and the definition of native windows and pixmaps which can also support client API rendering. This specification does not define the set of platforms that may be supported by the EGL implementation, nor does it specify behavior specific to any platform. The set of supported platforms and their behavior is defined by extensions. To detect if a particular platform is supported, clients should query the EGL_EXTENSIONS string of EGL_NO_DISPLAY using eglQueryString (see section 3.3).

2.1.1

EGL Types

EGLBoolean is an integral type representing a boolean value, and should only take on the values EGL_TRUE (1) and EGL_FALSE (0). If boolean parameters 1

Platforms were previously referred to as “native window systems”, but EGL 1.5 now supports both rendering without a display, and multiple runtime platforms.

2.1. NATIVE PLATFORMS AND RENDERING APIS

passed to EGL take on other values, behavior is undefined, although typically any non-zero value will be interpreted as EGL_TRUE. EGLint is an integral type, normally the same size as a native platform int. Legal attribute values whose type is boolean, bitmask, enumerant, or integer can be passed in EGLint attribute lists, but handle and pointer values may not be representable in such attribute lists2 . EGLAttrib is an integral type defined to be equivalent to the ISO C intptr_t type. It is used in the commands eglCreateImage, eglCreateSync, eglCreatePlatformWindowSurface, eglCreatePlatformPixmapSurface, eglGetPlatformDisplay, and eglGetSyncAttrib, and will be used for all similar commands in the future which take attribute lists or return attribute values, since such commands might at some point need to represent handle and pointer values in attribute lists as well as other integral types3 . EGLContext is an opaque type representing a client API context. The definition of contexts depends on the client API, but usually represents the state vector of an abstract machine describing the client API and allows executing client API commmands with respect to that state vector. EGLImage is an opaque type representing handles to EGLImage objects (see section 2.5). EGLSurface is an opaque type representing a drawing surface which client APIs can render content into. EGLSync is an opaque type representing handles to sync objects (see section 3.8.1). EGLTime is a 64-bit unsigned integer type representing a timeout interval in nanoseconds for eglClientWaitSync (see section 3.8.1.3).

2.1.2

Displays

Most EGL calls include an EGLDisplay parameter. This represents the abstract display on which graphics are drawn. In most environments a display corresponds 2

This is a functionality regression relative to earlier versions of EGL, first adopted in the November, 2013 EGL 1.4 update. It was adopted because EGL implementations on some 64-bit platforms chose their EGLint type to be a 32-bit integer type, and changing the definition would break their ABIs in a way considered to be too disruptive to their application base. The EGL_KHR_cl_event2 and EGL_KHR_lock_surface3 extensions replace similar earlier extensions allowing pointers in attribute lists, and work around this regression by providing new interfaces using attribute types which are guaranteed to be sufficiently large. New commands in EGL 1.5 taking attribute lists and returning attribute values use the EGLAttrib type (see below). 3 New interfaces using the new EGLAttrib type are not defined for older functionality such as creating pbuffers, since there is no current or expected requirement for pointer/handle-sized attributes in those interfaces.

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2.2. RENDERING CONTEXTS AND DRAWING SURFACES

to a single physical screen. The initialization routines described in section 3.2 include a method for querying a default display, and platform-specific EGL extensions may be defined to obtain other displays. All EGL objects are associated with an EGLDisplay, and exist in a namespace defined by that display. Objects are always specified by the combination of an EGLDisplay parameter with a parameter representing the handle of the object.

2.2

Rendering Contexts and Drawing Surfaces

The client API specifications are intentionally vague on how a rendering context (e.g. the state machine defined by a client API) is created. One of the purposes of EGL is to provide a means to create client API rendering contexts (henceforth simply referred to as contexts), and associate them with drawing surfaces. EGL defines several types of drawing surfaces collectively referred to as EGLSurfaces. These include windows, used for onscreen rendering; pbuffers, used for offscreen rendering; and pixmaps, used for offscreen rendering into buffers that may be accessed through native APIs. EGL windows and pixmaps are tied to platform windows and pixmaps. EGLSurfaces are created with respect to an EGLConfig. The EGLConfig describes the depth of the color buffer components and the types, quantities and sizes of the ancillary buffers (i.e., the depth, multisample, and stencil buffers). Ancillary buffers are associated with an EGLSurface, not with a context. If several contexts are all writing to the same surface, they will share those buffers. Rendering operations to one window never affect the unobscured pixels of another window, or the corresponding pixels of ancillary buffers of that window. Contexts for different client APIs all share the color buffer of a surface, but ancillary buffers are not necessarily meaningful for every client API. In particular, depth, multisample, and stencil buffers are currently used only by OpenGL and OpenGL ES. A context can be used with any EGLSurface that it is compatible with (subject to the restrictions discussed in the section on address space). A surface and context are compatible if: • They support the same type of color buffer (RGB or luminance). • They have color buffers and ancillary buffers of the same depth. Depth is measured per-component. For example, color buffers in RGB565 and RGBA4444 formats have the same aggregate depth of 16 bits/pixel, but are not compatible because their per-component depths are different.

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2.2. RENDERING CONTEXTS AND DRAWING SURFACES

Ancillary buffers not meaningful to a client API do not affect compatibility; for example, a surface with both color and stencil buffers will be compatible with an OpenVG context so long as the color buffers associated with the contexts are of the same depth. The stencil buffer is irrelevant because OpenVG does not use it. • The surface was created with respect to an EGLConfig supporting client API rendering of the same type as the API type of the context (in environments supporting multiple client APIs). • They were created with respect to the same EGLDisplay (in environments supporting multiple displays). As long as the compatibility constraint and the address space requirement are satisfied, clients can render into the same EGLSurface using different contexts. It is also possible to use a single context to render into multiple EGLSurfaces.

2.2.1

Using Rendering Contexts

OpenGL and OpenGL ES define both client state and server state. Thus an OpenGL or OpenGL ES context consists of two parts: one to hold the client state and one to hold the server state. OpenVG does not separate client and server state. The OpenGL, OpenGL ES, and OpenVG client APIs rely on an implicit context used by all entry points, rather than passing an explicit context parameter. The implicit context for each API is set with EGL calls (see section 3.7.3). The implicit contexts used by these APIs are called current contexts. Each thread can have at most one current rendering context for each supported client API; for example, there may be both a current OpenGL ES context and a current OpenVG context in an implementation supporting both of these APIs. In addition, a context can be current to only one thread at a time. The client is responsible for creating contexts and surfaces. Because OpenGL and OpenGL ES contexts share many entry points, additional restrictions on current contexts exists for these client APIs when both are supported (see section 3.7).

2.2.2

Rendering Models

EGL, OpenGL, and OpenGL ES support two rendering models: back buffered and single buffered. Back buffered rendering is used by window and pbuffer surfaces. Memory for the color buffer used during rendering is allocated and owned by EGL. When the

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2.2. RENDERING CONTEXTS AND DRAWING SURFACES

client is finished drawing a frame, the back buffer may be copied to a visible window using eglSwapBuffers. Pbuffer surfaces have a back buffer but no associated window, so the back buffer need not be copied. Single buffered rendering is used by pixmap surfaces. Memory for the color buffer is specified at surface creation time in the form of a native pixmap, and client APIs are required to use that memory during rendering. When the client is finished drawing a frame, the native pixmap contains the final image. Pixmap surfaces typically do not support multisampling, since the native pixmap used as the color buffer is unlikely to provide space to store multisample information. Some client APIs, such as OpenGL and OpenVG, also support single buffered rendering to window surfaces. This behavior can be selected when creating the window surface, as defined in section 3.5.1. When mixing use of client APIs which do not support single buffered rendering into windows, like OpenGL ES, with client APIs which do support it, back color buffers and visible window contents must be kept consistent when binding window surfaces to contexts for each API type (see section 3.7.3). Both back and single buffered surfaces may also be copied to a specified native pixmap using eglCopyBuffers. 2.2.2.1

Native Surface Coordinate Systems

The coordinate system for native windows and pixmaps in most platforms is inverted relative to the OpenGL, OpenGL ES, and OpenVG client API coordinate systems. In such systems, native windows and pixmaps have (0, 0) in the upper left of the pixmap, while the client APIs have (0, 0) in the lower left. To accomodate this, client API rendering to window and pixmap surfaces must invert their own y coordinate when accessing the color buffer in the underlying native window or pixmap, so that the resulting images appear as intended by the application when the final image is displayed by eglSwapBuffers or copied from a pixmap to a visible window using native rendering APIs. 2.2.2.2

Window Resizing

EGL window surfaces need to be resized when their corresponding native window is resized. Implementations typically use hooks into the OS and platform to perform this resizing on demand, transparently to the client. Some implementations may instead define an EGL extension giving explicit control of surface resizing. Implementations which cannot resize EGL window surfaces on demand must instead respond to native window size changes in eglSwapBuffers (see section 3.10.3).

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2.3. DIRECT RENDERING AND ADDRESS SPACES

2.2.3

Interaction With Native Rendering

Native rendering will always be supported by pixmap surfaces (to the extent that native rendering APIs can draw to native pixmaps). Pixmap surfaces are typically used when mixing native and client API rendering is desirable, since there is no need to move data between the back buffer visible to the client APIs and the native pixmap visible to native rendering APIs. However, pixmap surfaces may, for the same reason, have restricted capabilities and performance relative to window and pbuffer surfaces. Native rendering will not be supported by pbuffer surfaces, since the color buffers of pbuffers are allocated internally by EGL and are not accessible through any other means. Native rendering may be supported by window surfaces, but only if the platform has a compatible rendering model allowing it to share the back color buffer, or if single buffered rendering to the window surface is being done. When both native rendering APIs and client APIs are drawing into the same underlying surface, no guarantees are placed on the relative order of completion of operations in the different rendering streams other than those provided by the synchronization primitives discussed in section 3.8. Some state is shared between client APIs and the underlying platform and rendering APIs, including color buffer values in window and pixmap surfaces.

2.3

Direct Rendering and Address Spaces

EGL is assumed to support only direct rendering, unlike similar APIs such as GLX. EGL objects and related context state cannot be used outside of the address space in which they are created. In a single-threaded environment, each process has its own address space. In a multi-threaded environment, all threads may share the same virtual address space; however, this capability is not required, and implementations may choose to restrict their address space to be per-thread even in an environment supporting multiple application threads. Context state, including both the client and server state of OpenGL and OpenGL ES contexts, exists in the client’s address space; this state cannot be shared by a client in another process. Support of indirect rendering (in those environments where this concept makes sense) may have the effect of relaxing these limits on sharing. However, such support is beyond the scope of this document.

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2.4. SHARED STATE

2.4

Shared State

Most context state is small. However, some types of state are potentially large and/or expensive to copy, in which case it may be desirable for multiple contexts to share such state rather than replicating it in each context. Such state may only be shared between different contexts of the same API type (e.g. two OpenGL contexts, two OpenGL ES contexts, or two OpenVG contexts, but not a mixture). EGL provides for sharing certain types of context state among contexts existing in a single address space. The types of client API objects that are shareable are defined by the corresponding client API specifications.

2.4.1

OpenGL and OpenGL ES Texture Objects

Texture state can be encapsulated in a named texture object. A texture object is created by binding an unused name to one of the supported texture targets (GL_TEXTURE_2D, GL_TEXTURE_3D, or GL_TEXTURE_CUBE_MAP) of OpenGL or OpenGL ES context. When a texture object is bound, operations on the target to which it is bound affect the bound texture object, and queries of the target to which it is bound return state from the bound texture object. OpenGL and OpenGL ES makes no attempt to synchronize access to texture objects. If a texture object is bound to more than one context, then it is up to the programmer to ensure that the contents of the object are not being changed via one context while another context is using the texture object for rendering. The results of changing a texture object while another context is using it are undefined. All modifications to shared context state as a result of executing glBindTexture are atomic. Also, a texture object will not be deleted while it is still bound to any context.

2.4.2

OpenGL and OpenGL ES Buffer Objects

If a OpenGL or OpenGL ES buffer object is bound to more than one context, then it is up to the programmer to ensure that the contents of the object are not being changed via one context while another context is using the buffer object for rendering. The results of changing a buffer object while another context is using it are undefined. All modifications to shared context state as a result of executing glBindBuffer are atomic. Also, a buffer object will not be deleted while it is still bound to any context.

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2.5. EGLIMAGES

2.5

EGLImages

As described in section 2.4, EGL allows contexts of the same client API type to share significant amounts of state (such as OpenGL and OpenGL ES texture objects, or OpenVG paths); however, in some cases it may be desirable to share state between client APIs. An example is using a previously-rendered OpenVG image as an OpenGL ES texture object. In order to facilitate these more complicated use-cases, EGL is capable of creating EGL resources that can be shared between contexts of different client APIs (called EGLImages) from client API resources such as texel arrays in OpenGL ES texture objects or OpenVG VGImages. Collectively, the resources that are used to create EGLImages are referred to as EGLImage sources. The EGL client APIs each provide mechanisms for creating appropriate resource types (such as complete texture arrays or OpenVG VGImages) from EGLImages through API-specific mechanisms. Collectively, resources which are created from EGLImages within client APIs are referred to as EGLImage targets. Each EGLImage may have multiple associated EGLImage targets. Collectively, the EGLImage source and EGLImage targets associated with an EGLImage object are referred to as EGLImage siblings. Commands to create, manage, and destroy EGLImages are described in section 3.9.

2.6

Multiple Threads

EGL and its client APIs must be threadsafe. Interrupt routines may not share a context with their main thread. EGL guarantees sequentiality within a command stream for each of its client APIs, but not between these APIs and native APIs which may also be rendering into the same surface. It is possible, for example, that a native drawing command issued by a single threaded client after an OpenGL ES command might be executed before that OpenGL ES command. Client API commands are not guaranteed to be atomic. Some such commands might otherwise impair interactive use of the platform by the user. For instance, rendering a large texture mapped polygon on a system with no graphics hardware, or drawing a large OpenGL ES vertex array, could prevent a user from popping up a menu soon enough to be usable. Synchronization is in the hands of the client. It can be maintained at moderate cost with the judicious use of commands such as glFinish, vgFinish, eglWaitClient, and eglWaitNative, as well as (if they exist) synchronization commands

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2.7. POWER MANAGEMENT

present in native rendering APIs. Client API and native rendering can be done in parallel so long as the client does not preclude it with explicit synchronization calls. Some performance degradation may be experienced if needless switching between client APIs and native rendering is done.

2.7

Power Management

Power management events can occur asynchronously while an application is running. When the system returns from the power management event the EGLContext will be invalidated, and all subsequent client API calls will have no effect (as if no context is bound). Errors Following a power management event, calls to eglSwapBuffers, eglCopyBuffers, or eglMakeCurrent will indicate failure by returning EGL_FALSE. The error EGL_CONTEXT_LOST will be returned if a power management event has occurred. On detection of this error, the application must destroy all contexts (by calling eglDestroyContext for each context). To continue rendering the application must recreate any contexts it requires, and subsequently restore any client API state and objects it wishes to use. Any EGLSurfaces that the application has created need not be destroyed following a power management event, but their contents will be invalid. Note that not all implementations can be made to generate power management events, and developers should continue to refer to platform-specific documentation in this area. We expected continued work in platform-specific extensions to enable more control over power management issues, including event detection, scope and nature of resource loss, behavior of EGL and client API calls under resource loss, and recommended techniques for recovering from events. Future versions of EGL may incorporate additional functionality in this area.

2.8

Extensions

EGL implementations may expose additional functionality beyond that described by this specification. Additional functionality may include new functions, new enumerant values, and extended behavior for existing functions. Implementations ad-

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2.8. EXTENSIONS

vertise such extensions to EGL by exposing extension strings, which are queryable with eglQueryString. Each EGL extension belongs to exactly one of the following types: Display Extension A display extension adds functionality to an individual EGLDisplay. Different instances of EGLDisplay may support different sets of display extensions. Client Extension A client extension adds functionality that is independent of any display. In other words, it adds functionality to the EGL client library itself. In a given process, there exists exactly one set, possibly empty, of supported client extensions. When the client extension string is first queried, that set becomes immutable.

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Chapter 3

EGL Functions and Errors 3.1

Errors

Where possible, when an EGL function fails it has no side effects. EGL functions usually return an indicator of success or failure; either an EGLBoolean EGL_TRUE or EGL_FALSE value, or in the form of an out-of-band return value indicating failure, such as returning EGL_NO_CONTEXT instead of a requested context handle. Additional information about the success or failure of the most recent EGL function called in a specific thread1 , in the form of an error code, can be obtained by calling EGLint eglGetError(void); The error codes that may be returned from eglGetError, and their meanings, are: EGL_SUCCESS

Function succeeded. EGL_NOT_INITIALIZED

EGL is not initialized, or could not be initialized, for the specified display. Any command may generate this error. EGL_BAD_ACCESS

EGL cannot access a requested resource (for example, a context is bound in 1

Note that calling eglGetError twice without any other intervening EGL calls will always return

EGL_SUCCESS on the second call, since eglGetError is itself an EGL function, and the second call is reporting the success or failure of the first call. In other words, error checking must always be performed immediately after an EGL function fails.

3.1. ERRORS

another thread). Any command accessing a named resource may generate this error. EGL_BAD_ALLOC

EGL failed to allocate resources for the requested operation. Any command allocating resources may generate this error. EGL_BAD_ATTRIBUTE

An unrecognized attribute or attribute value was passed in an attribute list. Any command taking an attribute parameter or attribute list may generate this error. EGL_BAD_CONTEXT

An EGLContext argument does not name a valid EGLContext. Any command taking an EGLContext parameter may generate this error. EGL_BAD_CONFIG

An EGLConfig argument does not name a valid EGLConfig. Any command taking an EGLConfig parameter may generate this error. EGL_BAD_CURRENT_SURFACE

The current surface of the calling thread is a window, pbuffer, or pixmap that is no longer valid. EGL_BAD_DISPLAY

An EGLDisplay argument does not name a valid EGLDisplay. Any command taking an EGLDisplay parameter may generate this error. EGL_BAD_SURFACE

An EGLSurface argument does not name a valid surface (window, pbuffer, or pixmap) configured for rendering. Any command taking an EGLSurface parameter may generate this error. EGL_BAD_MATCH

Arguments are inconsistent; for example, an otherwise valid context requires buffers (e.g. depth or stencil) not allocated by an otherwise valid surface. EGL_BAD_PARAMETER

One or more argument values are invalid. Any command taking parameters may generate this error. EGL_BAD_NATIVE_PIXMAP

An EGLNativePixmapType argument does not refer to a valid native EGL 1.5 - August 27, 2014

3.1. ERRORS

pixmap. Any command taking an EGLNativePixmapType parameter may generate this error. EGL_BAD_NATIVE_WINDOW

An EGLNativeWindowType argument does not refer to a valid native window. Any command taking an EGLNativeWindowType parameter may generate this error. EGL_CONTEXT_LOST

A power management event has occurred. The application must destroy all contexts and reinitialise client API state and objects to continue rendering, as described in section 2.7. Any command may generate this error. When an EGL function could potentially generate several different errors (for example, when passed both a bad attribute name, and a bad attribute value for a legal attribute name), the implementation may choose to generate any one of the applicable errors. When there is no status to return (in other words, when eglGetError is called as the first EGL call in a thread, or immediately after calling eglReleaseThread), EGL_SUCCESS will be returned.

3.1.1

Generic Errors Are Not Described Repeatedly

Some specific error codes that may be generated by a failed EGL function, and their meanings, are described together with each function. However, not all possible errors are described with each function. Errors whose meanings are identical across many functions (such as returning EGL_BAD_DISPLAY or EGL_NOT_INITIALIZED for an unsuitable EGLDisplay argument) may not be described repeatedly. Some of the error codes above describe a class of commands which may generate them. Such errors are not necessarily described repeatedly together with each such command in the class.

3.1.2

Parameter Validation

EGL normally checks the validity of objects passed into it, but detecting invalid native objects (pixmaps, windows, and displays) may not always be possible. Specifying such invalid handles may result in undefined behavior, although implementations should generate EGL_BAD_NATIVE_PIXMAP and EGL_BAD_NATIVE_WINDOW errors if possible.

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3.2. INITIALIZATION

3.2

Initialization

A display can be obtained by calling EGLDisplay eglGetPlatformDisplay(EGLenum platform, void *native_display, const EGLAttrib *attrib_list); The resulting EGLDisplay belongs to the native platform specified by platform. This specification defines no valid values for platform. Any specification that does define a valid value for platform will also define requirements for the native display parameter. For example, an extension specification that defines support for the X11 platform may require that native display be a pointer to an X11 Display, and an extension specification that defines support for the Microsoft Windows platform may require that native display be a pointer to a Windows Device Context. All attribute names in attrib list are immediately followed by the corresponding desired value. The list is terminated with EGL_NONE. The attrib list is considered empty if either attrib list is NULL or if its first element is EGL_NONE. This specification defines no valid attribute names for attrib list. Multiple calls made to eglGetPlatformDisplay with the same parameters will return the same EGLDisplay handle. If platform is valid but no display matching native display is available, then EGL_NO_DISPLAY is returned; no error condition is raised in this case. Errors eglGetPlatformDisplay returns EGL_NO_DISPLAY on failure. An EGL_BAD_PARAMETER error is generated if platform has an invalid value. A display can also be obtained by calling EGLDisplay eglGetDisplay(EGLNativeDisplayType display_id); The behavior of eglGetDisplay is similar to that of eglGetPlatformDisplay, but is specified in terms of implementation-specific behavior rather than platformspecific extensions. As for eglGetPlatformDisplay, EGL considers the returned EGLDisplay as belonging to the same platform as display id. However, the set of platforms to which display id is permitted to belong, as well as the actual type of EGL 1.5 - August 27, 2014

3.2. INITIALIZATION

display id, are implementation-specific. If display id is EGL_DEFAULT_DISPLAY, a default display is returned. Multiple calls made to eglGetDisplay with the same display id will return the same EGLDisplay handle. If no display matching display id is available, EGL_NO_DISPLAY is returned; no error condition is raised in this case. EGL may be initialized on a display by calling EGLBoolean eglInitialize(EGLDisplay dpy, EGLint *major, EGLint *minor); EGL_TRUE is returned on success, and major and minor are updated with the major

and minor version numbers of the EGL implementation (for example, in an EGL 1.2 implementation, the values of *major and *minor would be 1 and 2, respectively). major and minor are not updated if they are specified as NULL. Initializing an already-initialized display is allowed, but the only effect of such a call is to return EGL_TRUE and update the EGL version numbers. An initialized display may be used from other threads in the same address space without being initialized again in those threads. Errors eglInitialize returns EGL_FALSE on failure, and major and minor are not updated. An EGL_BAD_DISPLAY error is generated if the dpy argument does not refer to a valid EGLDisplay. An EGL_NOT_INITIALIZED error is generated if EGL cannot be initialized for an otherwise valid dpy. To release resources associated with use of EGL and client APIs on a display, call EGLBoolean eglTerminate(EGLDisplay dpy); Termination marks all EGL-specific resources, such as contexts and surfaces, associated with the specified display for deletion. Handles to all such resources are invalid as soon as eglTerminate returns, but the dpy handle itself remains valid. Passing such handles to any other EGL command will generate EGL_BAD_SURFACE or EGL_BAD_CONTEXT errors. Applications should not try to perform useful work

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3.2. INITIALIZATION

with such resources following eglTerminate; only eglMakeCurrent or eglReleaseThread should be called, to complete deletion of these resources. 2 If contexts or surfaces, created with respect to dpy are current (see section 3.7.3) to any thread, then they are not actually destroyed while they remain current. If other resources created with respect to dpy are in use by any current context or surface, then they are also not destroyed until the corresponding context or surface is no longer current. All such resources will be destroyed as soon as eglReleaseThread is called from the thread they are bound to, or eglMakeCurrent is called from that thread with the current rendering API (see section 3.7) set such that the current context is affected. Use of bound contexts and surfaces (that is, continuing to issue commands to a bound client API context) will not result in interruption or termination of applications, but rendering results are undefined, and client APIs may generate errors. Errors eglTerminate returns EGL_FALSE on failure. If the dpy argument does not refer to a valid EGLDisplay, an EGL_BAD_DISPLAY error is generated. Termination of a display that has already been terminated, or has not yet been initialized, is allowed, but the only effect of such a call is to return EGL_TRUE, since there are no EGL resources associated with the display to release. A terminated display may be re-initialized by calling eglInitialize again. When re-initializing a terminated display, resources which were marked for deletion as a result of the earlier termination remain so marked, and handles which previously referred to them remain invalid At any point a display may either be initialized or uninitialized. All displays start out uninitialized. A display becomes initialized after eglInitialize is successfully called on it. A display becomes uninitialized after eglTerminate is successfully called on it. An uninitialized display may be passed to the functions eglInitialize, eglTerminate, and in some cases eglMakeCurrent. All other EGL functions which take a display argument will fail and generate an EGL_NOT_2

Immediately invalidating handles is a subtle behavior change. Prior to the January 13, 2009 release of the EGL 1.4 Specification, handles remained valid so long as the underlying surface was current. In the September 18, 2010 release, handle invalidation was explicitly extended to all EGL resources associated with dpy, not just contexts and surfaces.

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3.3. EGL QUERIES

INITIALIZED error when passed a valid but uninitialized display. 3

3.3

EGL Queries const char *eglQueryString(EGLDisplay dpy, EGLint name);

eglQueryString returns a pointer to a static, zero-terminated string describing some aspect of the EGL implementation running on the specified display. name may be one of EGL_CLIENT_APIS, EGL_EXTENSIONS, EGL_VENDOR, or EGL_VERSION. The EGL_CLIENT_APIS string describes which client APIs are supported. It is zero-terminated and contains a space-separated list of API names, which must include at least one of ‘‘OpenGL’’, ‘‘OpenGL_ES’’ or ‘‘OpenVG’’. The EGL_EXTENSIONS string describes the set of supported EGL extensions. The string is zero-terminated and contains a space-separated list of extension names; extension names themselves do not contain spaces. If there are no extensions, then the empty string is returned. If dpy is EGL_NO_DISPLAY, then the EGL_EXTENSIONS string describes the set of supported client extensions. If dpy is a valid, initialized display, then the EGL_EXTENSIONS string describes the set of display extensions supported by that display. The set of supported client extensions is disjoint from the set of extensions supported by any given display (see section 2.8). The format and contents of the EGL_VENDOR string is implementation dependent. The format of the EGL_VERSION string is: <major version.minor version><space><vendor specific info> Both the major and minor portions of the version number are numeric. Their values must match the major and minor values returned by eglInitialize (see section 3.2). The vendor-specific information is optional; if present, its format and contents are implementation specific. If dpy is EGL_NO_DISPLAY, then the EGL_VERSION string describes the supported client version. If dpy is a valid, initialized display, then the EGL_VERSION string describes the supported EGL version for dpy. The client version indicates 3 Note that once an EGLDisplay is created, the handle will necessarily remain valid for the lifetime of the application, although the corresponding display may be repeatedly initialized and terminated.

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3.4. CONFIGURATION MANAGEMENT

that all EGL entry points which are needed for the supported client APIs are available at runtime, while the display version indicates which EGL functionality is supported for a display. Errors On failure, NULL is returned. An EGL_BAD_DISPLAY error is generated if dpy is not a valid display, unless dpy is EGL_NO_DISPLAY and name is EGL_EXTENSIONS or EGL_VERSION. An EGL_NOT_INITIALIZED error is generated if dpy is a valid but uninitialized display. An EGL_BAD_PARAMETER error is generated if name is not one of the values described above.

3.4

Configuration Management

An EGLConfig describes the format, type and size of the color buffers and ancillary buffers for an EGLSurface. If the EGLSurface is a window, then the EGLConfig describing it may have an associated native visual type. Names of EGLConfig attributes are shown in table 3.1. These names may be passed to eglChooseConfig to specify required attribute properties. EGL_CONFIG_ID is a unique integer identifying different EGLConfigs. Configuration IDs must be small positive integers starting at 1 and ID assignment should be compact; that is, if there are N EGLConfigs defined by the EGL implementation, their configuration IDs should be in the range [1, N ]. Small gaps in the sequence are allowed, but should only occur when removing configurations defined in previous revisions of an EGL implementation. Buffer Descriptions and Attributes The various buffers that may be contained by an EGLSurface, and the EGLConfig attributes controlling their creation, are described below. Attribute values include the depth of these buffers, expressed in bits/pixel component. If the depth of a buffer in an EGLConfig is zero, then an EGLSurface created with respect to that EGLConfig will not contain the corresponding buffer. Not all buffers are used or required by all client APIs. To conserve resources, implementations may delay creation of buffers until they are needed by EGL or a client API. For example, if an EGLConfig describes an alpha mask buffer with EGL 1.5 - August 27, 2014

3.4. CONFIGURATION MANAGEMENT Attribute EGL_BUFFER_SIZE

Type integer

EGL_RED_SIZE EGL_GREEN_SIZE EGL_BLUE_SIZE EGL_LUMINANCE_SIZE EGL_ALPHA_SIZE EGL_ALPHA_MASK_SIZE EGL_BIND_TO_TEXTURE_RGB EGL_BIND_TO_TEXTURE_RGBA EGL_COLOR_BUFFER_TYPE EGL_CONFIG_CAVEAT EGL_CONFIG_ID EGL_CONFORMANT

integer integer integer integer integer integer boolean boolean enum enum integer bitmask

EGL_DEPTH_SIZE EGL_LEVEL EGL_MAX_PBUFFER_WIDTH EGL_MAX_PBUFFER_HEIGHT EGL_MAX_PBUFFER_PIXELS EGL_MAX_SWAP_INTERVAL EGL_MIN_SWAP_INTERVAL EGL_NATIVE_RENDERABLE

integer integer integer integer integer integer integer boolean

EGL_NATIVE_VISUAL_ID

integer

EGL_NATIVE_VISUAL_TYPE

integer

EGL_RENDERABLE_TYPE EGL_SAMPLE_BUFFERS EGL_SAMPLES EGL_STENCIL_SIZE EGL_SURFACE_TYPE

bitmask integer integer integer bitmask

EGL_TRANSPARENT_TYPE EGL_TRANSPARENT_RED_VALUE EGL_TRANSPARENT_GREEN_VALUE EGL_TRANSPARENT_BLUE_VALUE

enum integer integer integer

20 Notes total color component bits in the color buffer bits of Red in the color buffer bits of Green in the color buffer bits of Blue in the color buffer bits of Luminance in the color buffer bits of Alpha in the color buffer bits of Alpha Mask in the mask buffer True if bindable to RGB textures. True if bindable to RGBA textures. color buffer type any caveats for the configuration unique EGLConfig identifier whether contexts created with this config are conformant bits of Z in the depth buffer frame buffer level maximum width of pbuffer maximum height of pbuffer maximum size of pbuffer maximum swap interval minimum swap interval EGL_TRUE if native rendering APIs can render to surface handle of corresponding native visual native visual type of the associated visual which client APIs are supported number of multisample buffers number of samples per pixel bits of Stencil in the stencil buffer which types of EGL surfaces are supported. type of transparency supported transparent red value transparent green value transparent blue value

Table 3.1: EGLConfig attributes. EGL 1.5 - August 27, 2014

3.4. CONFIGURATION MANAGEMENT

depth greater than zero, that buffer need not be allocated by a surface until an OpenVG context is bound to that surface. The Color Buffer The color buffer contains pixel color values, and is shared by all client APIs rendering to a surface. EGL_COLOR_BUFFER_TYPE indicates the color buffer type, and must be either EGL_RGB_BUFFER for an RGB color buffer, or EGL_LUMINANCE_BUFFER for a luminance color buffer. For an RGB buffer, EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE must be non-zero, and EGL_LUMINANCE_SIZE must be zero. For a luminance buffer, EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE must be zero, and EGL_LUMINANCE_SIZE must be non-zero. For both RGB and luminance color buffers, EGL_ALPHA_SIZE may be zero or non-zero (the latter indicates the existence of a destination alpha buffer). If OpenGL or OpenGL ES rendering is supported for a luminance color buffer (as described by the value of the EGL_RENDERABLE_TYPE attribute, described below), it is treated as RGB rendering with the value of GL_RED_BITS equal to EGL_LUMINANCE_SIZE and the values of GL_GREEN_BITS and GL_BLUE_BITS equal to zero. The red component of fragments is written to the luminance channel of the color buffer, the green and blue components are discarded, and the alpha component is written to the alpha channel of the color buffer (if present). EGL_BUFFER_SIZE gives the total of the color component bits of the color buffer4 For an RGB color buffer, the total is the sum of EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE, and EGL_ALPHA_SIZE. For a luminance color buffer, the total is the sum of EGL_LUMINANCE_SIZE and EGL_ALPHA_SIZE. The Alpha Mask Buffer The alpha mask buffer is used only by OpenVG. EGL_ALPHA_MASK_SIZE indicates the depth of this buffer. The Depth Buffer The depth buffer is shared by OpenGL and OpenGL ES. It contains fragment depth (Z) information generated during rasterization. EGL_DEPTH_SIZE indicates the depth of this buffer in bits. 4

The value of EGL_BUFFER_SIZE does not include any padding bits that may be present in the pixel format, nor does it account for any alignment or padding constraints of surfaces, so it cannot be reliably used to compute the memory consumed by a surface. No such query exists in EGL 1.4.

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3.4. CONFIGURATION MANAGEMENT

The Stencil Buffer The stencil buffer is shared by OpenGL and OpenGL ES. It contains fragment stencil information generated during rasterization. EGL_STENCIL_SIZE indicates the depth of this buffer in bits. The Multisample Buffer The multisample buffer may be shared by OpenGL, OpenGL ES and OpenVG, although such sharing cannot be guaranteed (see comments at the end of section 3.7.3.1 for more information about sharing the multisample buffer). It contains multisample information (color values, and possibly stencil and depth values) generated by multisample rasterization. The format of the multisample buffer is not specified, and its contents are not directly accessible. Only the existence of the multisample buffer, together with the number of samples it contains, are exposed by EGL. Operations such as posting a surface with eglSwapBuffers (see section 3.10.1, copying a surface with eglCopyBuffers (see section 3.10.2), reading from the color buffer using client API commands, and binding a client API context to a surface (see section 3.7.3), may cause resolution of the multisample buffer to the color buffer. Multisample resolution combines and filters per-sample information in the multisample buffer to create per-pixel colors stored in the color buffer. The details of this filtering process are normally chosen by the implementation, but under some circumstances may be controlled on a per-surface basis using eglSurfaceAttrib (see section 3.5.6). EGL_SAMPLE_BUFFERS indicates the number of multisample buffers, which must be zero or one. EGL_SAMPLES gives the number of samples per pixel; if EGL_SAMPLE_BUFFERS is zero, then EGL_SAMPLES will also be zero. If EGL_SAMPLE_BUFFERS is one, then the number of color, depth, and stencil bits for each sample in the multisample buffer are as specified by the EGL_*_SIZE attributes. There are no single-sample depth or stencil buffers for a multisample EGLConfig; the only depth and stencil buffers are those in the multisample buffer. If the color samples in the multisample buffer store fewer bits than are stored in the color buffers, this fact will not be reported accurately. Presumably a compression scheme is being employed, and is expected to maintain an aggregate resolution equal to that of the color buffers. Other EGLConfig Attribute Descriptions

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3.4. CONFIGURATION MANAGEMENT EGL Token Name EGL_WINDOW_BIT EGL_PIXMAP_BIT EGL_PBUFFER_BIT EGL_MULTISAMPLE_RESOLVE_BOX_BIT EGL_SWAP_BEHAVIOR_PRESERVED_BIT EGL_VG_COLORSPACE_LINEAR_BIT EGL_VG_ALPHA_FORMAT_PRE_BIT

23 Description EGLConfig supports windows EGLConfig supports pixmaps EGLConfig supports pbuffers EGLConfig supports box filtered multisample resolve EGLConfig supports setting swap behavior for color buffers EGLConfig supports OpenVG rendering in linear colorspace EGLConfig supports OpenVG rendering with premultiplied alpha

Table 3.2: Types of surfaces supported by an EGLConfig

EGL_SURFACE_TYPE is a mask indicating capabilities of surfaces that can be

created with the corresponding EGLConfig (the config is said to support these surface types). The valid bit settings are shown in Table 3.2. For example, an EGLConfig for which the value of the EGL_SURFACE_TYPE attribute is EGL_WINDOW_BIT | EGL_PIXMAP_BIT | EGL_PBUFFER_BIT can be used to create any type of EGL surface, while an EGLConfig for which this attribute value is EGL_WINDOW_BIT cannot be used to create a pbuffer or pixmap. EGL_SURFACE_TYPE is EGL_WINDOW_BIT. If EGL_MULTISAMPLE_RESOLVE_BOX_BIT is set in EGL_SURFACE_TYPE, then the EGL_MULTISAMPLE_RESOLVE attribute of a surface can be specified as a box filter with eglSurfaceAttrib (see section 3.5.6). If EGL_SWAP_BEHAVIOR_PRESERVED_BIT is set in EGL_SURFACE_TYPE, then the EGL_SWAP_BEHAVIOR attribute of a surface can be specified to preserve color buffer contents using eglSurfaceAttrib (see section 3.5.6). If EGL_VG_COLORSPACE_LINEAR_BIT is set in EGL_SURFACE_TYPE, then the EGL_VG_COLORSPACE attribute may be set to EGL_VG_COLORSPACE_LINEAR when creating a window, pixmap, or pbuffer surface (see section 3.5). If EGL_VG_ALPHA_FORMAT_PRE_BIT is set in EGL_SURFACE_TYPE, then the EGL_VG_ALPHA_FORMAT attribute may be set to EGL_VG_ALPHA_FORMAT_PRE when creating a window, pixmap, or pbuffer surface (see section 3.5). EGL_RENDERABLE_TYPE is a mask indicating which client APIs can render into a surface created with respect to an EGLConfig. The valid bit settings are

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3.4. CONFIGURATION MANAGEMENT EGL Token Name EGL_OPENGL_BIT EGL_OPENGL_ES_BIT EGL_OPENGL_ES2_BIT EGL_OPENGL_ES3_BIT EGL_OPENVG_BIT

Client API and Version Supported OpenGL OpenGL ES 1.x OpenGL ES 2.x OpenGL ES 3.x OpenVG 1.x

Table 3.3: Types of client APIs supported by an EGLConfig

shown in Table 3.3. Creation of a client API context based on an EGLConfig will fail unless the EGLConfig’s EGL_RENDERABLE_TYPE attribute include the bit corresponding to that API and version. EGL_NATIVE_RENDERABLE is an EGLBoolean indicating whether the platform can be used to render into a surface created with the EGLConfig. Constraints on native rendering are discussed in more detail in sections 2.2.2 and 2.2.3. If an EGLConfig supports windows then it may have an associated native visual. EGL_NATIVE_VISUAL_ID specifies an identifier for this visual, and EGL_NATIVE_VISUAL_TYPE specifies its type. If an EGLConfig does not support windows, or if there is no associated native visual type, then querying EGL_NATIVE_VISUAL_ID will return 0 and querying EGL_NATIVE_VISUAL_TYPE will return EGL_NONE. The interpretation of the native visual identifier and type is platform-dependent. For example, if the platform is X11, then the identifier will be the XID of an X Visual. The EGL_CONFIG_CAVEAT attribute may be set to one of the following values: EGL_NONE, EGL_SLOW_CONFIG or EGL_NON_CONFORMANT_CONFIG. If the attribute is set to EGL_NONE then the configuration has no caveats; if it is set to EGL_SLOW_CONFIG then rendering to a surface with this configuration may run at reduced performance (for example, the hardware may not support the color buffer depths described by the configuration); if it is set to EGL_NON_CONFORMANT_CONFIG then rendering to a surface with this configuration will not pass the required OpenGL ES conformance tests (note that EGL_NON_CONFORMANT_CONFIG is obsolete, and the same information can be obtained from the EGL_CONFORMANT attribute on a per-client-API basis, not just for OpenGL ES). API conformance requires that a set of EGLConfigs supporting certain defined minimum attributes (such as the number, type, and depth of supported buffers) be supplied by any conformant implementation. Those requirements are

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3.4. CONFIGURATION MANAGEMENT

documented only in the conformance specifications for client APIs. EGL_CONFORMANT is a mask indicating if a client API context created with respect to the corresponding EGLConfig will pass the required conformance tests for that API. The valid bit settings are the same as for EGL_RENDERABLE_TYPE, as defined in table 3.3, but the presence or absence of each client API bit determines whether the corresponding context will be conformant or non-conformant. 5 EGL_LEVEL is the framebuffer overlay or underlay level in which an EGLSurface created with respect to an on-screen native window (see section 3.5.1) will be placed. Level zero indicates the default layer. The behavior of windows placed in overlay and underlay levels depends on the underlying platform. EGL_TRANSPARENT_TYPE indicates whether or not a configuration supports transparency. If the attribute is set to EGL_NONE then windows created with the EGLConfig will not have any transparent pixels. If the attribute is EGL_TRANSPARENT_RGB, then the EGLConfig supports transparency; a transparent pixel will be drawn when the red, green and blue values which are read from the framebuffer are equal to EGL_TRANSPARENT_RED_VALUE, EGL_TRANSPARENT_GREEN_VALUE and EGL_TRANSPARENT_BLUE_VALUE, respectively. If EGL_TRANSPARENT_TYPE is EGL_NONE, then the values for EGL_TRANSPARENT_RED_VALUE, EGL_TRANSPARENT_GREEN_VALUE, and EGL_TRANSPARENT_BLUE_VALUE are undefined. Otherwise, they are interpreted as integer framebuffer values between 0 and the maximum framebuffer value for the component. For example, EGL_TRANSPARENT_RED_VALUE will range between 0 and 2EGL_RED_SIZE − 1. EGL_MAX_PBUFFER_WIDTH and EGL_MAX_PBUFFER_HEIGHT indicate the maximum width and height that can be passed into eglCreatePbufferSurface, and EGL_MAX_PBUFFER_PIXELS indicates the maximum number of pixels (width times height) for a pbuffer surface. Note that an implementation may return a value for EGL_MAX_PBUFFER_PIXELS that is less than the maximum width times the maximum height. The value for EGL_MAX_PBUFFER_PIXELS is static and assumes that no other pbuffers or native resources are contending for the framebuffer memory. Thus it may not be possible to allocate a pbuffer of the size given by EGL_MAX_PBUFFER_PIXELS. EGL_MAX_SWAP_INTERVAL is the maximum value that can be passed to eglSwapInterval, and indicates the number of swap intervals that will elapse before a buffer swap takes place after calling eglSwapBuffers. Larger values will be 5 Most EGLConfigs should be conformant for all supported client APIs. Conformance requirements limit the number of non-conformant configs that an implementation can define.

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3.4. CONFIGURATION MANAGEMENT

silently clamped to this value. EGL_MIN_SWAP_INTERVAL is the minimum value that can be passed to eglSwapInterval, and indicates the number of swap intervals that will elapse before a buffer swap takes place after calling eglSwapBuffers. Smaller values will be silently clamped to this value. EGL_BIND_TO_TEXTURE_RGB and EGL_BIND_TO_TEXTURE_RGBA are booleans indicating

whether the color buffers of a pbuffer created with the EGLConfig can be bound to a OpenGL ES RGB or RGBA texture respectively. Currently only pbuffers can be bound as textures, so these attributes may only be EGL_TRUE if the value of the EGL_SURFACE_TYPE attribute includes EGL_PBUFFER_BIT. It is possible to bind a RGBA visual to a RGB texture, in which case the values in the alpha component of the visual are ignored when the color buffer is used as a RGB texture. Implementations may choose not to support EGL_BIND_TO_TEXTURE_RGB for RGBA visuals. Texture binding to OpenGL textures is not supported.

3.4.1

Querying Configurations

Use EGLBoolean eglGetConfigs(EGLDisplay dpy, EGLConfig *configs, EGLint config_size, EGLint *num_config); to get the list of all EGLConfigs that are available on the specified display. configs is a pointer to a buffer containing config size elements. On success, EGL_TRUE is returned. The number of configurations is returned in num config, and elements 0 through num conf ig − 1 of configs are filled in with the valid EGLConfigs. No more than config size EGLConfigs will be returned even if more are available on the specified display. However, if eglGetConfigs is called with configs = NULL, then no configurations are returned, but the total number of configurations available will be returned in num config. Errors On failure, EGL_FALSE is returned. An EGL_NOT_INITIALIZED error is generated if EGL is not initialized on dpy. An EGL_BAD_PARAMETER error is generated if num config is NULL.

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3.4. CONFIGURATION MANAGEMENT

Use EGLBoolean eglChooseConfig(EGLDisplay dpy, const EGLint *attrib_list, EGLConfig *configs, EGLint config_size, EGLint *num_config); to get EGLConfigs that match a list of attributes. The return value and the meaning of configs, config size, and num config are the same as for eglGetConfigs. However, only configurations matching attrib list, as discussed below, will be returned. Errors On failure, EGL_FALSE is returned. An EGL_BAD_ATTRIBUTE error is generated if attrib list contains an undefined EGL attribute or an attribute value that is unrecognized or out of range. All attribute names in attrib list are immediately followed by the corresponding desired value. The list is terminated with EGL_NONE. If an attribute is not specified in attrib list, then the default value (shown in Table 3.4) is used (it is said to be specified implicitly). If EGL_DONT_CARE is specified as an attribute value, then the attribute will not be checked. EGL_DONT_CARE may be specified for all attributes except EGL_LEVEL and EGL_MATCH_NATIVE_PIXMAP. If attrib list is NULL or empty (first attribute is EGL_NONE), then selection and sorting of EGLConfigs is done according to the default criteria in Tables 3.4 and 3.1, as described below in sections 3.4.1.1 and 3.4.1.2. 3.4.1.1

Selection of EGLConfigs

Attributes are matched in an attribute-specific manner, as shown in the ”Selection Critera” column of table 3.4. The criteria shown in the table have the following meanings: AtLeast Only EGLConfigs with an attribute value that meets or exceeds the specified value are selected. Exact Only EGLConfigs whose attribute value equals the specified value are matched. Mask Only EGLConfigs for which the bits set in the attribute value include all the bits that are set in the specified value are selected (additional bits might

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3.4. CONFIGURATION MANAGEMENT

be set in the attribute value)6 . Special As described for the specific attribute. Some of the attributes must match the specified value exactly; others, such as EGL_RED_SIZE, must meet or exceed the specified minimum values.

To retrieve an EGLConfig given its unique integer ID, use the EGL_CONFIG_ID attribute. When EGL_CONFIG_ID is specified, all other attributes are ignored, and only the EGLConfig with the given ID is returned. If EGL_MAX_PBUFFER_WIDTH, EGL_MAX_PBUFFER_HEIGHT, EGL_MAX_PBUFFER_PIXELS, or EGL_NATIVE_VISUAL_ID are specified in attrib list, then they are ignored (however, if present, these attributes must still be followed by an attribute value in attrib list). If EGL_SURFACE_TYPE is specified in attrib list and the mask that follows does not have EGL_WINDOW_BIT set, or if there are no native visual types, then the EGL_NATIVE_VISUAL_TYPE attribute is ignored. If EGL_TRANSPARENT_TYPE is set to EGL_NONE in attrib list, then the EGL_TRANSPARENT_RED_VALUE, EGL_TRANSPARENT_GREEN_VALUE, and EGL_TRANSPARENT_BLUE_VALUE attributes are ignored. If EGL_MATCH_NATIVE_PIXMAP is specified in attrib list, it must be followed by an attribute value which is the handle of a valid native pixmap. Only EGLConfigs which support rendering to that pixmap will match this attribute7 . If no EGLConfig matching the attribute list exists, then the call succeeds, but num config is set to 0. 3.4.1.2

Sorting of EGLConfigs

If more than one matching EGLConfig is found, then a list of EGLConfigs is returned. The list is sorted by proceeding in ascending order of the ”Sort Priority” column of table 3.4. That is, configurations that are not ordered by a lower numbered rule are sorted by the next higher numbered rule. Sorting for each rule is either numerically Smaller or Larger as described in the ”Sort Order” column, or a Special sort order as described for each sort rule below: 1. Special: by EGL_CONFIG_CAVEAT where the precedence is EGL_NONE, EGL_SLOW_CONFIG, EGL_NON_CONFORMANT_CONFIG. 6

Some readers have found this phrasing confusing. Another way to think of it to say that any bits present in the mask attribute must also be present in the EGLConfig attribute. Thus, setting a mask attribute value of zero means that all configs will match that value. 7 The special match criteria for EGL_MATCH_NATIVE_PIXMAP was introduced due to the difficulty of determining an EGLConfig equivalent to a native pixmap using only color component depths.

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3.4. CONFIGURATION MANAGEMENT

Attribute

Default

Selection Criteria

Sort Order

Sort Priority

EGL_BUFFER_SIZE EGL_RED_SIZE EGL_GREEN_SIZE EGL_BLUE_SIZE EGL_LUMINANCE_SIZE EGL_ALPHA_SIZE EGL_ALPHA_MASK_SIZE EGL_BIND_TO_TEXTURE_RGB EGL_BIND_TO_TEXTURE_RGBA EGL_COLOR_BUFFER_TYPE EGL_CONFIG_CAVEAT EGL_CONFIG_ID EGL_CONFORMANT EGL_DEPTH_SIZE EGL_LEVEL EGL_MATCH_NATIVE_PIXMAP EGL_MAX_SWAP_INTERVAL EGL_MIN_SWAP_INTERVAL EGL_NATIVE_RENDERABLE EGL_NATIVE_VISUAL_TYPE EGL_RENDERABLE_TYPE EGL_SAMPLE_BUFFERS EGL_SAMPLES EGL_STENCIL_SIZE EGL_SURFACE_TYPE EGL_TRANSPARENT_TYPE EGL_TRANSPARENT_RED_VALUE EGL_TRANSPARENT_GREEN_VALUE EGL_TRANSPARENT_BLUE_VALUE

0 0 0 0 0 0 0

AtLeast AtLeast AtLeast AtLeast AtLeast AtLeast AtLeast Exact Exact Exact Exact Special Mask AtLeast Exact Special Exact Exact Exact Exact Mask AtLeast AtLeast AtLeast Mask Exact Exact Exact Exact

Smaller Special Special Special Special Special Smaller None None Special Special Smaller None Smaller None None None None None Special None Smaller Smaller Smaller None None None None None

4 3 3 3 3 3 9

EGL_DONT_CARE EGL_DONT_CARE EGL_RGB_BUFFER EGL_DONT_CARE EGL_DONT_CARE

0 0 0 EGL_NONE EGL_DONT_CARE EGL_DONT_CARE EGL_DONT_CARE EGL_DONT_CARE EGL_OPENGL_ES_BIT

0 0 0 EGL_WINDOW_BIT EGL_NONE EGL_DONT_CARE EGL_DONT_CARE EGL_DONT_CARE

Table 3.4: Default values and match criteria for EGLConfig attributes.

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2 1 11 (last) 7

10 5 6 8

3.4. CONFIGURATION MANAGEMENT

2. Special: by EGL_COLOR_BUFFER_TYPE where the precedence is EGL_RGB_BUFFER, EGL_LUMINANCE_BUFFER. 3. Special: by larger total number of color bits (for an RGB color buffer, this is the sum of EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE, and EGL_ALPHA_SIZE; for a luminance color buffer, the sum of EGL_LUMINANCE_SIZE and EGL_ALPHA_SIZE)8 . If the requested number of bits in attrib list for a particular color component is 0 or EGL_DONT_CARE, then the number of bits for that component is not considered. 4. Smaller EGL_BUFFER_SIZE. 5. Smaller EGL_SAMPLE_BUFFERS. 6. Smaller EGL_SAMPLES. 7. Smaller EGL_DEPTH_SIZE. 8. Smaller EGL_STENCIL_SIZE. 9. Smaller EGL_ALPHA_MASK_SIZE. 10. Special: by EGL_NATIVE_VISUAL_TYPE (the actual sort order is implementation-defined, depending on the meaning of native visual types). 11. Smaller EGL_CONFIG_ID (this is always the last sorting rule, and guarantees a unique ordering). EGLConfigs are not sorted with respect to the parameters EGL_BIND_TO_TEXTURE_RGB, EGL_BIND_TO_TEXTURE_RGBA, EGL_CONFORMANT, EGL_LEVEL, EGL_NATIVE_RENDERABLE, EGL_MAX_SWAP_INTERVAL, EGL_MIN_SWAP_INTERVAL, EGL_RENDERABLE_TYPE, EGL_SURFACE_TYPE, EGL_TRANSPARENT_TYPE, EGL_TRANSPARENT_RED_VALUE, EGL_TRANSPARENT_GREEN_VALUE, and EGL_TRANSPARENT_BLUE_VALUE. 8 This rule places configs with deeper color buffers first in the list returned by eglChooseConfig. Applications may find this counterintuitive if they expect configs with smaller buffer sizes to be returned first. For example, if an implementation has two configs with RGBA depths of 8888 and 5650, and the application specifies RGBA sizes of 1110, the 8888 config will be returned first. To avoid this rule altogether, specify 0 or EGL_DONT_CARE for each component size. In this case this rule will be ignored, and rule 4, which prefers configs with a smaller EGL_BUFFER_SIZE, will apply.

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3.4.2

Lifetime of Configurations

Configuration handles (EGLConfigs) returned by eglGetConfigs and eglChooseConfig remain valid so long as the EGLDisplay from which the handles were obtained is not terminated. Implementations supporting a large number of different configurations, where it might be burdensome to instantiate data structures for each configuration so queried (but never used), may choose to return handles encoding sufficient information to instantiate the corresponding configurations dynamically, when needed to create EGL resources or query configuration attributes.

3.4.3

Querying Configuration Attributes

To get the value of an EGLConfig attribute, use EGLBoolean eglGetConfigAttrib(EGLDisplay dpy, EGLConfig config, EGLint attribute, EGLint *value); If eglGetConfigAttrib succeeds then it returns EGL_TRUE and the value for the specified attribute is returned in value. Errors On failure eglGetConfigAttrib returns EGL_FALSE. If attribute is not a valid attribute then EGL_BAD_ATTRIBUTE is generated. attribute may be any of the EGL attributes shown in tables 3.1 and 3.4, with the exception of EGL_MATCH_NATIVE_PIXMAP.

3.5

Rendering Surfaces

3.5.1

Creating On-Screen Rendering Surfaces

To create an on-screen rendering surface, first create a native platform window whose pixel format corresponds to the format, type, and size of the color buffers required by config. On some implementations, the pixel format of the native win-

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3.5. RENDERING SURFACES

dow must match that of the EGLConfig9 . Other implementations may allow any native window and config to correspond, even if their formats differ10 . The command EGLSurface eglCreatePlatformWindowSurface(EGLDisplay dpy, EGLConfig config, void *native_window, const EGLAttrib *attrib_list); creates an onscreen EGLSurface and returns a handle to it. Any EGL context created with a compatible EGLConfig can be used to render into this surface. native window must belong to the same platform as dpy, and EGL considers the returned EGLSurface as belonging to that same platform. The EGL extension that defines the platform to which dpy belongs also defines the requirements for the native window parameter. attrib list specifies a list of attributes for the window. The list has the same structure as described for eglChooseConfig. Attributes that can be specified in attrib list include EGL_GL_COLORSPACE, EGL_RENDER_BUFFER, EGL_VG_COLORSPACE, and EGL_VG_ALPHA_FORMAT. It is possible that some platforms will define additional attributes specific to those environments, as an EGL extension. attrib list may be NULL or empty (first attribute is EGL_NONE), in which case all attributes assumes their default value as described below. EGL_RENDER_BUFFER specifies which buffer should be used by default for client API rendering to the window, as described in section 2.2.2. If its value is EGL_SINGLE_BUFFER, then client APIs should render directly into the visible window. If its value is EGL_BACK_BUFFER, then all client APIs should render into the back buffer. The default value of EGL_RENDER_BUFFER is EGL_BACK_BUFFER. Client APIs may not be able to respect the requested rendering buffer. To determine the actual buffer that a context will render to by default, call eglQueryContext with attribute EGL_RENDER_BUFFER (see section 3.7.4). 9

The exact definition of matching formats is implementation-dependent, but usually means the color format (which of R, G, B, and A components are present), type (EGL expects unsigned integer color components), and size (number of bits/component) are the same. For example, X11-based EGL implementations often require the native window to have an X visual ID whose format matches config in this fashion. 10 It may still be desirable for the native window and config to have matching formats, even if the implementation does not require this. Otherwise potentially costly operations such as format conversion during eglSwapBuffers may be required.

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3.5. RENDERING SURFACES

Some client APIs expose the ability to switch between rendering to the front or the back buffer. In this case eglQueryContext does not reflect such changes, and will report the buffer used as a render target when the context was first created, which may not be the same as the current render target for that buffer. Some platforms may not allow rendering directly to the front buffer of a window surface. When such windows are made current to a context, the context will always have an EGL_RENDER_BUFFER attribute value of EGL_BACK_BUFFER. From the client API point of view these surfaces have only a back buffer and no front buffer, similar to pbuffer rendering (see section 2.2.2). Client APIs which generally have the ability to switch render target from back to front will not be able to do so when the platform does not allow this; from the point of view of the client API the front buffer for such windows does not exist. EGL_GL_COLORSPACE specifies the color space used by OpenGL and OpenGL ES when rendering to the surface11 . If its value is EGL_GL_COLORSPACE_SRGB, then a non-linear, perceptually uniform color space is assumed, with a corresponding GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING value of GL_SRGB. If its value is EGL_GL_COLORSPACE_LINEAR, then a linear color space is assumed, with a corresponding GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING value of GL_LINEAR. The default value of EGL_GL_COLORSPACE is EGL_GL_COLORSPACE_LINEAR. Note that the EGL_GL_COLORSPACE attribute is used only by OpenGL and OpenGL ES contexts supporting sRGB framebuffers. EGL itself does not distinguish multiple colorspace models. Refer to the “sRGB Conversion” sections of the OpenGL 4.4 and OpenGL ES 3.0 specifications for more information. EGL_VG_COLORSPACE specifies the color space used by OpenVG when rendering to the surface. If its value is EGL_VG_COLORSPACE_sRGB, then a non-linear, perceptually uniform color space is assumed, with a corresponding VGImageFormat of form VG_s*. If its value is EGL_VG_COLORSPACE_LINEAR, then a linear color space is assumed, with a corresponding VGImageFormat of form VG_l*. The default value of EGL_VG_COLORSPACE is EGL_VG_COLORSPACE_sRGB. EGL_VG_ALPHA_FORMAT specifies how alpha values are interpreted by OpenVG when rendering to the surface. If its value is EGL_VG_ALPHA_FORMAT_NONPRE, then alpha values are not premultipled. If its value is EGL_VG_ALPHA_11 Only OpenGL and OpenGL ES contexts which support sRGB rendering must respect requests for EGL_GL_COLORSPACE_SRGB, and only to sRGB formats supported by the context (normally just SRGB8) Older versions not supporting sRGB rendering will ignore this surface attribute. Applications using OpenGL must additionally enable GL_FRAMEBUFFER_SRGB to perform sRGB rendering, even when an sRGB surface is bound; this enable is not required (or supported) for OpenGL ES.

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3.5. RENDERING SURFACES

FORMAT_PRE, then alpha values are premultiplied. The default value of EGL_VG_ALPHA_FORMAT is EGL_VG_ALPHA_FORMAT_NONPRE. Note that the EGL_VG_COLORSPACE and EGL_VG_ALPHA_FORMAT attributes

are used only by OpenVG. EGL itself does not distinguish multiple colorspace models. Refer to section 11.2 of the OpenVG 1.0 specification for more information. Similarly, the EGL_VG_ALPHA_FORMAT attribute does not necessarily control or affect the platform’s interpretation of alpha values, even when the platform makes use of alpha to composite surfaces at display time. The platform’s use and interpretation of alpha values is outside the scope of EGL. However, the preferred behavior is for platforms to ignore the value of EGL_VG_ALPHA_FORMAT when compositing window surfaces. If dpy and native window do not belong to the same platform, then undefined behavior occurs (see section 3.1.2). Errors On failure eglCreatePlatformWindowSurface returns EGL_NO_SURFACE. If the pixel format of native window does not correspond to the format, type, and size of the color buffers required by config, as discussed above, then an EGL_BAD_MATCH error is generated. If config does not support rendering to windows (the EGL_SURFACE_TYPE attribute does not contain EGL_WINDOW_BIT), an EGL_BAD_MATCH error is generated. If config does not support the OpenVG colorspace or alpha format attributes specified in attrib list (as defined for eglCreatePlatformWindowSurface), an EGL_BAD_MATCH error is generated. If config is not a valid EGLConfig, an EGL_BAD_CONFIG error is generated. If native window is not a valid native window handle, then an EGL_BAD_NATIVE_WINDOW error should be generated. If there is already an EGLSurface associated with native window (as a result of a previous eglCreatePlatformWindowSurface call), then an EGL_BAD_ALLOC error is generated. If the implementation cannot allocate resources for the new EGL window, an EGL_BAD_ALLOC error is generated. An on-screen rendering surface may also be created by calling

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3.5. RENDERING SURFACES

EGLSurface eglCreateWindowSurface(EGLDisplay dpy, EGLConfig config, EGLNativeWindowType win, const EGLint *attrib_list); The behavior of eglCreateWindowSurface is identical to that of eglCreatePlatformWindowSurface except that the set of platforms to which dpy is permitted to belong, as well as the actual type of win, are implementation specific.

3.5.2

Creating Off-Screen Rendering Surfaces

EGL supports off-screen rendering surfaces in pbuffers. Pbuffers differ from windows in the following ways: 1. Pbuffers are typically allocated in offscreen (non-visible) graphics memory and are intended only for accelerated offscreen rendering. Allocation can fail if there are insufficient graphics resources (implementations are not required to virtualize framebuffer memory). Clients should deallocate pbuffers when they are no longer in use, since graphics memory is often a scarce resource. 2. Pbuffers are EGL resources and have no associated native window or native window type. It may not be possible to render to pbuffers using native rendering APIs. To create a pbuffer, call EGLSurface eglCreatePbufferSurface(EGLDisplay dpy, EGLConfig config, const EGLint *attrib_list); This creates a single pbuffer surface and returns a handle to it. attrib list specifies a list of attributes for the pbuffer. The list has the same structure as described for eglChooseConfig. Attributes that can be specified in attrib list include EGL_WIDTH, EGL_HEIGHT, EGL_LARGEST_PBUFFER, EGL_TEXTURE_FORMAT, EGL_TEXTURE_TARGET, EGL_MIPMAP_TEXTURE, EGL_GL_COLORSPACE, EGL_VG_COLORSPACE, and EGL_VG_ALPHA_FORMAT. It is possible that some platforms will define additional attributes specific to those environments, as an EGL extension. attrib list may be NULL or empty (first attribute is EGL_NONE), in which case all the attributes assume their default values as described below. EGL_WIDTH and EGL_HEIGHT specify the pixel width and height of the rectangular pbuffer. If the value of EGLConfig attribute EGL_TEXTURE_FORMAT is EGL 1.5 - August 27, 2014

3.5. RENDERING SURFACES

not EGL_NO_TEXTURE, then the pbuffer width and height specify the size of the level zero texture image. The default values for EGL_WIDTH and EGL_HEIGHT are zero. EGL_TEXTURE_FORMAT specifies the format of the OpenGL ES texture that will be created when a pbuffer is bound to a texture map. It can be set to EGL_TEXTURE_RGB, EGL_TEXTURE_RGBA, or EGL_NO_TEXTURE. The default value of EGL_TEXTURE_FORMAT is EGL_NO_TEXTURE. EGL_TEXTURE_TARGET specifies the target for the OpenGL ES texture that will be created when the pbuffer is created with a texture format of EGL_TEXTURE_RGB or EGL_TEXTURE_RGBA. The target can be set to EGL_NO_TEXTURE or EGL_TEXTURE_2D. The default value of EGL_TEXTURE_TARGET is EGL_NO_TEXTURE. EGL_MIPMAP_TEXTURE indicates whether storage for OpenGL ES mipmaps should be allocated. Space for mipmaps will be set aside if the attribute value is EGL_TRUE and EGL_TEXTURE_FORMAT is not EGL_NO_TEXTURE. The default value for EGL_MIPMAP_TEXTURE is EGL_FALSE. Use EGL_LARGEST_PBUFFER to get the largest available pbuffer when the allocation of the pbuffer would otherwise fail. The width and height of the allocated pbuffer will never exceed the values of EGL_WIDTH and EGL_HEIGHT, respectively. If the pbuffer will be used as a OpenGL ES texture (i.e., the value of EGL_TEXTURE_TARGET is EGL_TEXTURE_2D, and the value of EGL_TEXTURE_FORMAT is EGL_TEXTURE_RGB or EGL_TEXTURE_RGBA), then the aspect ratio will be preserved and the new width and height will be valid sizes for the texture target (e.g. if the underlying OpenGL ES implementation does not support non-power-of-two textures, both the width and height will be a power of 2). Use eglQuerySurface to retrieve the dimensions of the allocated pbuffer. The default value of EGL_LARGEST_PBUFFER is EGL_FALSE. EGL_GL_COLORSPACE, EGL_VG_COLORSPACE and EGL_VG_ALPHA_FORMAT have the same meaning and default values as when used with eglCreatePlatformWindowSurface. The resulting pbuffer will contain color buffers and ancillary buffers as specified by config. The contents of the depth and stencil buffers may not be preserved when rendering an OpenGL ES texture to the pbuffer and switching which image of the texture is rendered to (e.g., switching from rendering one mipmap level to rendering another). Errors On failure eglCreatePbufferSurface returns EGL_NO_SURFACE. EGL 1.5 - August 27, 2014

3.5. RENDERING SURFACES

If the pbuffer could not be created due to insufficient resources, then an EGL_BAD_ALLOC error is generated.

If config is not a valid EGLConfig, an EGL_BAD_CONFIG error is generated. If the value specified for either EGL_WIDTH or EGL_HEIGHT is less than zero, an EGL_BAD_PARAMETER error is generated. If config does not support pbuffers, an EGL_BAD_MATCH error is generated. An EGL_BAD_MATCH error is generated if any of the following conditions are true: • The EGL_TEXTURE_FORMAT attribute is not EGL_NO_TEXTURE, and EGL_WIDTH and/or EGL_HEIGHT specify an invalid size (e.g., the texture size is not a power of two, and the underlying OpenGL ES implementation does not support non-power-of-two textures). • The EGL_TEXTURE_FORMAT attribute is EGL_NO_TEXTURE, and EGL_TEXTURE_TARGET is something other than EGL_NO_TEXTURE; or, EGL_TEXTURE_FORMAT is something other than EGL_NO_TEXTURE, and EGL_TEXTURE_TARGET is EGL_NO_TEXTURE. Finally, an EGL_BAD_ATTRIBUTE error is generated if any of the EGL_TEXTURE_FORMAT, EGL_TEXTURE_TARGET, or EGL_MIPMAP_TEXTURE attributes are specified, but config does not support OpenGL ES rendering (e.g. the EGL_RENDERABLE_TYPE attribute does not include at least one of EGL_OPENGL_ES_BIT, EGL_OPENGL_ES2_BIT, or EGL_OPENGL_ES3_BIT,

3.5.3

Binding Off-Screen Rendering Surfaces To Client Buffers

Pbuffers may also be created by binding renderable buffers created in client APIs to EGL. Currently, the only client API resources which may be bound in this fashion are OpenVGVGImage objects. To bind a client API renderable buffer to a pbuffer, call EGLSurface eglCreatePbufferFromClientBuffer(EGLDisplay dpy, EGLenum buftype, EGLClientBuffer buffer, EGLConfig config, const EGLint *attrib_list); This creates a single pbuffer surface bound to the specified buffer for part or all of its buffer storage, and returns a handle to it. The width and height of the pbuffer are determined by the width and height of buffer.

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3.5. RENDERING SURFACES

buftype specifies the type of buffer to be bound. The only allowed value of buftype is EGL_OPENVG_IMAGE. buffer is a client API reference to the buffer to be bound. When buftype is EGL_OPENVG_IMAGE, buffer must be a valid VGImage handle, cast into the type EGLClientBuffer. attrib list specifies a list of attributes for the pbuffer. The list has the same structure as described for eglChooseConfig. Attributes that can be specified in attrib list include EGL_TEXTURE_FORMAT, EGL_TEXTURE_TARGET, and EGL_MIPMAP_TEXTURE. The meaning of these attributes is as described above for eglCreatePbufferSurface. The EGL_VG_COLORSPACE and EGL_VG_ALPHA_FORMAT attributes of the surface are determined by the VGImageFormat of buffer. attrib list may be NULL or empty (first attribute is EGL_NONE), in which case all the attributes assume their default values as described above for eglCreatePbufferSurface. The resulting pbuffer will contain color and ancillary buffers as specified by config. Buffers which are present in buffer (normally, just the color buffer) will be bound to EGL. Buffers which are not present in buffer (such as depth and stencil, if config includes those buffers) will be allocated by EGL in the same fashion as for a surface created with eglCreatePbufferSurface Errors On failure eglCreatePbufferFromClientBuffer returns EGL_NO_SURFACE.

In addition to the errors described above for eglCreatePbufferSurface, eglCreatePbufferFromClientBuffer may fail and generate errors for the following reasons: If buftype is not a recognized client API resource type (e.g. is not EGL_OPENVG_IMAGE), an EGL_BAD_PARAMETER error is generated. If buffer is not a valid handle or name of a client API resource of the specified buftype in the currently bound context corresponding to that type, an EGL_BAD_PARAMETER error is generated. If the buffers contained in buffer do not correspond to a proper subset of the buffers described by config, and match the bit depths for those buffers specified in config, then an EGL_BAD_MATCH error is generated. For example, a VGImage with pixel format VG_lRGBA_8888 corresponds to an EGLConfig with EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE, and EGL_ALPHA_SIZE values of 8. If the buffers contained in buffer consist of any EGLImage siblings, an EGL 1.5 - August 27, 2014

3.5. RENDERING SURFACES

EGL_BAD_ACCESS error is generated.

If no context corresponding to the specified buftype is current, an EGL_BAD_ACCESS error is generated. There may be additional constraints on which types of buffers may be bound to EGL surfaces, as described in client API specifications. If those constraints are violated, then an EGL_BAD_MATCH error is generateda . If buffer is already bound to another pbuffer, or is in use by a client API as discussed below, an EGL_BAD_ACCESS error is generated. a

An example of such an additional constraint is an implementation which cannot support an OpenVGVGImage being bound to a pbuffer which will be used as a mipmapped OpenGL ES texture (e.g. whose EGL_MIPMAP_TEXTURE attribute is EGL_TRUE).

3.5.3.1

Lifetime and Usage of Bound Buffers

Binding client API buffers to EGL pbuffers create the possibility of race conditions, and of buffers being deleted through one API while still in use in another API. To avoid these problems, a number of constraints apply to bound client API buffers: • Bound buffers may be used exclusively by either EGL, or the client API that originally created them. For example, if a VGImage is bound to a pbuffer, and that pbuffer is bound to any client API rendering context, then the VGImage may not be used as the explicit source or destination of any OpenVG operation. Errors resulting from such use are described in client API specifications. Similarly, while a VGImage is in use by OpenVG, the pbuffer it is bound to may not be made current to any client API context, as described in section 3.7.3. • Binding a buffer creates an additional reference to it, and implementations must respect outstanding references when destroying objects. For example, if a VGImage is bound to a pbuffer, destroying the image with vgDestroyImage will not free the underlying buffer, because it is still in use by EGL. However, following vgDestroyImage the buffer may only be referred to via the EGL pbuffer handle, since the OpenVG handle to that buffer no longer exists. Similarly, destroying the pbuffer with eglDestroySurface will not free the underlying buffer, because it is still in use by OpenVG. However, following eglDestroySurface the buffer may only be referred to via the OpenVGVGImage handle, since the EGL pbuffer handle no longer exists. EGL 1.5 - August 27, 2014

3.5. RENDERING SURFACES

3.5.4

Creating Native Pixmap Rendering Surfaces

EGL also supports rendering surfaces whose color buffers are stored in native pixmaps. Pixmaps differ from windows in that they are typically allocated in offscreen (non-visible) graphics or CPU memory. Pixmaps differ from pbuffers in that they do have an associated native pixmap and native pixmap type, and it may be possible to render to pixmaps using APIs other than client APIs. To create a pixmap rendering surface, first create a native platform pixmap, then select an EGLConfig matching the pixel format of that pixmap (calling eglChooseConfig with an attribute list including EGL_MATCH_NATIVE_PIXMAP returns only EGLConfigs matching the pixmap specified in the attribute list - see section 3.4.1). The command EGLSurface eglCreatePlatformPixmapSurface(EGLDisplay dpy, EGLConfig config, void *native_pixmap, const EGLAttrib *attrib_list); creates an offscreen EGLSurface and returns a handle to it. Any EGL context created with a compatible EGLConfig can be used to render into this surface. native pixmap must belong to the same platform as dpy, and EGL considers the returned EGLSurface as belonging to that same platform. The extension that defines the platform to which dpy belongs also defines the requirements for the native pixmap parameter. attrib list specifies a list of attributes for the pixmap. The list has the same structure as described for eglChooseConfig. Attributes that can be specified in attrib list include EGL_GL_COLORSPACE, EGL_VG_COLORSPACE and EGL_VG_ALPHA_FORMAT. It is possible that some platforms will define additional attributes specific to those environments, as an EGL extension. attrib list may be NULL or empty (first attribute is EGL_NONE), in which case all attributes assumes their default value. EGL_GL_COLORSPACE, EGL_VG_COLORSPACE and EGL_VG_ALPHA_FORMAT have the same meaning and default values as when used with eglCreatePlatformWindowSurface. The resulting pixmap surface will contain color and ancillary buffers as specified by config. Buffers which are present in pixmap (normally, just the color buffer) will be bound to EGL. Buffers which are not present in pixmap (such as depth and stencil, if config includes those buffers) will be allocated by EGL in the same fashion as for a surface created with eglCreatePbufferSurface.

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3.5. RENDERING SURFACES

If dpy and native pixmap do not belong to the same platform, then undefined behavior occurs (see section 3.1.2). Errors On

failure

eglCreatePlatformPixmapSurface

returns

EGL_NO_-

SURFACE.

If the attributes of pixmap do not correspond to config, then an EGL_BAD_MATCH error is generated. If config does not support rendering to pixmaps (the EGL_SURFACE_TYPE attribute does not contain EGL_PIXMAP_BIT), an EGL_BAD_MATCH error is generated. If config does not support the colorspace or alpha format attributes specified in attrib list (as defined for eglCreatePlatformWindowSurface), an EGL_BAD_MATCH error is generated. If config is not a valid EGLConfig, an EGL_BAD_CONFIG error is generated. If pixmap is not a valid native pixmap handle, then an EGL_BAD_NATIVE_PIXMAP error should be generated. If there is already an EGLSurface associated with pixmap (as a result of a previous eglCreatePlatformPixmapSurface call), then a EGL_BAD_ALLOC error is generated. Finally, if the implementation cannot allocate resources for the new EGL pixmap, an EGL_BAD_ALLOC error is generated. An offscreen rendering surface may also be created by calling EGLSurface eglCreatePixmapSurface(EGLDisplay dpy, EGLConfig config, EGLNativePixmapType pixmap, const EGLint *attrib_list); The behavior of eglCreatePixmapSurface is identical to that of eglCreatePlatformPixmapSurface except that the set of platforms to which dpy is permitted to belong, as well as the actual type of pixmap, are implementation specific.

3.5.5

Destroying Rendering Surfaces

An EGLSurface of any type (window, pbuffer, or pixmap) is destroyed by calling EGLBoolean eglDestroySurface(EGLDisplay dpy, EGLSurface surface); EGL 1.5 - August 27, 2014

3.5. RENDERING SURFACES

All resources associated with surface which were allocated by EGL are marked for deletion as soon as possible. Following eglDestroySurface, the surface and the handle referring to it are treated in the same fashion as a surface destroyed by eglTerminate (see section 3.2). Resources associated with surface but not allocated by EGL, such as native windows, native pixmaps, or client API buffers, are not affected when the surface is destroyed. Only storage actually allocated by EGL is marked for deletion. Furthermore, resources associated with a pbuffer surface are not released until all color buffers of that pbuffer bound to a OpenGL ES texture object have been released. Errors eglDestroySurface returns EGL_FALSE on failure. An EGL_BAD_SURFACE error is generated if surface is not a valid rendering surface.

3.5.6

Surface Attributes

To set an attribute for an EGLSurface, call EGLBoolean eglSurfaceAttrib(EGLDisplay dpy, EGLSurface surface, EGLint attribute, EGLint value); The specified attribute of surface is set to value. Attributes that can be specified are EGL_MIPMAP_LEVEL, EGL_MULTISAMPLE_RESOLVE, and EGL_SWAP_BEHAVIOR. If attribute is EGL_MIPMAP_LEVEL, then value indicates which level of the OpenGL ES mipmap texture should be rendered. If the value of this attribute is outside the range of supported mipmap levels, the closest valid mipmap level is selected for rendering. The initial value of this attribute is 0. If the value of pbuffer attribute EGL_TEXTURE_FORMAT is EGL_NO_TEXTURE, if the value of attribute EGL_TEXTURE_TARGET is EGL_NO_TEXTURE, or if surface is not a pbuffer, then attribute EGL_MIPMAP_LEVEL may be set, but has no effect. If attribute is EGL_MULTISAMPLE_RESOLVE, then value specifies the filter to use when resolving the multisample buffer. A value of EGL_MULTISAMPLE_RESOLVE_DEFAULT chooses the default implementation-defined filtering method, while EGL_MULTISAMPLE_RESOLVE_BOX chooses a one-pixel wide box filter placing equal weighting on all multisample values. EGL 1.5 - August 27, 2014

3.5. RENDERING SURFACES

If value is EGL_MULTISAMPLE_RESOLVE_BOX, and the EGL_SURFACE_TYPE attribute of the EGLConfig used to create surface does not contain EGL_MULTISAMPLE_RESOLVE_BOX_BIT, a EGL_BAD_MATCH error is generated. The initial value of EGL_MULTISAMPLE_RESOLVE is EGL_MULTISAMPLE_RESOLVE_DEFAULT. If attribute is EGL_SWAP_BEHAVIOR, then value specifies the effect on the color buffer of posting a surface with eglSwapBuffers (see section 3.10). A value of EGL_BUFFER_PRESERVED indicates that color buffer contents are unaffected, while EGL_BUFFER_DESTROYED indicates that color buffer contents may be destroyed or changed by the operation. If value is EGL_BUFFER_PRESERVED, and the EGL_SURFACE_TYPE attribute of the EGLConfig used to create surface does not contain EGL_SWAP_BEHAVIOR_PRESERVED_BIT, a EGL_BAD_MATCH error is generated. The initial value of EGL_SWAP_BEHAVIOR is chosen by the implementation. Errors eglSurfaceAttrib returns EGL_FALSE on failure. If OpenGL ES rendering is not supported by surface, then trying to set EGL_MIPMAP_LEVEL will cause an EGL_BAD_PARAMETER error. Other errors for specific attribute values are described above. To query an attribute associated with an EGLSurface call: EGLBoolean eglQuerySurface(EGLDisplay dpy, EGLSurface surface, EGLint attribute, EGLint *value); eglQuerySurface returns in value the value of attribute for surface. attribute must be set to one of the attributes in table 3.5. Querying EGL_CONFIG_ID returns the ID of the EGLConfig with respect to which the surface was created. Querying EGL_LARGEST_PBUFFER for a pbuffer surface returns the same attribute value specified when the surface was created with eglCreatePbufferSurface. For a window or pixmap surface, the contents of value are not modified. Querying EGL_WIDTH and EGL_HEIGHT returns respectively the width and height, in pixels, of the surface. For a window or pixmap surface, these values are initially equal to the width and height of the native window or pixmap with respect to which the surface was created. If a native window is resized, the corresponding window surface will eventually be resized by the implementation to match (as discussed in section 3.10.1). If there is a discrepancy because EGL has not yet resized EGL 1.5 - August 27, 2014

3.5. RENDERING SURFACES

Attribute

EGL_GL_COLORSPACE EGL_VG_ALPHA_FORMAT EGL_VG_COLORSPACE EGL_CONFIG_ID

Type enum enum enum integer

EGL_HEIGHT EGL_HORIZONTAL_RESOLUTION EGL_LARGEST_PBUFFER EGL_MIPMAP_TEXTURE EGL_MIPMAP_LEVEL EGL_MULTISAMPLE_RESOLVE EGL_PIXEL_ASPECT_RATIO EGL_RENDER_BUFFER EGL_SWAP_BEHAVIOR EGL_TEXTURE_FORMAT

integer integer boolean boolean integer enum integer enum enum enum

EGL_TEXTURE_TARGET EGL_VERTICAL_RESOLUTION EGL_WIDTH

enum integer integer

Description Color space for OpenGL and OpenGL ES Alpha format for OpenVG Color space for OpenVG ID of EGLConfig surface was created with Height of surface Horizontal dot pitch If true, create largest pbuffer possible True if texture has mipmaps Mipmap level to render to Multisample resolve behavior Display aspect ratio Render buffer Buffer swap behavior Format of texture: RGB, RGBA, or no texture Type of texture: 2D or no texture Vertical dot pitch Width of surface

Table 3.5: Queryable surface attributes and types.

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3.5. RENDERING SURFACES

the window surface, the size returned by eglQuerySurface will always be that of the EGL surface, not the corresponding native window. For a pbuffer, they will be the actual allocated size of the pbuffer (which may be less than the requested size if EGL_LARGEST_PBUFFER is EGL_TRUE). Querying EGL_HORIZONTAL_RESOLUTION and EGL_VERTICAL_RESOLUTION returns respectively the horizontal and vertical dot pitch of the display on which a window surface is visible. The values returned are equal to the actual dot pitch, in pixels/meter, multiplied by the constant value EGL_DISPLAY_SCALING (10000)12 . Querying EGL_PIXEL_ASPECT_RATIO returns the aspect ratio of an individual pixel (the ratio of a pixel’s width to its height), multiplied by EGL_DISPLAY_SCALING. For almost all displays, the returned value will be EGL_DISPLAY_SCALING, indicating an aspect ratio of one (square pixels). For an offscreen (pbuffer or pixmap) surface, or a surface whose pixel dot pitch or aspect ratio are unknown, querying EGL_HORIZONTAL_RESOLUTION, EGL_VERTICAL_RESOLUTION, and EGL_PIXEL_ASPECT_RATIO will return the constant value EGL_UNKNOWN (-1). Querying EGL_RENDER_BUFFER returns the buffer which client API rendering is requested to use. For a window surface, this is the same attribute value specified when the surface was created. For a pbuffer surface, it is always EGL_BACK_BUFFER. For a pixmap surface, it is always EGL_SINGLE_BUFFER. To determine the actual buffer being rendered to by a context, call eglQueryContext (see section 3.7.4). Querying EGL_MULTISAMPLE_RESOLVE returns the filtering method used when performing multisammple buffer resolution. The filter may be either EGL_MULTISAMPLE_RESOLVE_DEFAULT or EGL_MULTISAMPLE_RESOLVE_BOX, as described above for eglSurfaceAttrib. Querying EGL_SWAP_BEHAVIOR describes the effect on the color buffer when posting a surface with eglSwapBuffers (see section 3.10). Swap behavior may be either EGL_BUFFER_PRESERVED or EGL_BUFFER_DESTROYED, as described above for eglSurfaceAttrib. Querying EGL_TEXTURE_FORMAT, EGL_TEXTURE_TARGET, EGL_MIPMAP_TEXTURE, or EGL_MIPMAP_LEVEL for a non-pbuffer surface is not an error, but value is not modified.

EGL_DISPLAY_SCALING is used where EGL needs to return floating-point attribute values, which would normally be smaller than 1, as integers while still retaining sufficient precision to be meaningful.

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3.6. RENDERING TO TEXTURES

Errors eglQuerySurface returns EGL_FALSE on failure and value is not updated. If attribute is not a valid EGL surface attribute, then an EGL_BAD_ATTRIBUTE error is generated. If surface is not a valid EGLSurface, then an EGL_BAD_SURFACE error is generated.

3.6

Rendering to Textures

This section describes how to render to an OpenGL ES texture using a pbuffer surface configured for this operation. Errors If a pbuffer surface does not support OpenGL ES rendering, or if OpenGL ES is not implemented on a platform, then calling eglBindTexImage or eglReleaseTexImage will always generate EGL_BAD_SURFACE errors.

3.6.1

Binding a Surface to a OpenGL ES Texture

The command EGLBoolean eglBindTexImage(EGLDisplay dpy, EGLSurface surface, EGLint buffer); defines a two-dimensional texture image. The texture image consists of the image data in buffer for the specified surface, and need not be copied. Currently the only value accepted for buffer is EGL_BACK_BUFFER, which indicates the buffer into which OpenGL ES rendering is taking place (this is true even when using a singlebuffered surface, such as a pixmap). In future versions of EGL, additional buffer values may be allowed to bind textures to other buffers in an EGLSurface. The texture target, the texture format and the size of the texture components are derived from attributes of the specified surface, which must be a pbuffer supporting one of the EGL_BIND_TO_TEXTURE_RGB or EGL_BIND_TO_TEXTURE_RGBA attributes. Note that any existing images associated with the different mipmap levels of the texture object are freed (it is as if glTexImage was called with an image of zero width). EGL 1.5 - August 27, 2014

3.6. RENDERING TO TEXTURES Texture Component R G B A

47 Size EGL_RED_SIZE EGL_GREEN_SIZE EGL_BLUE_SIZE EGL_ALPHA_SIZE

Table 3.6: Size of texture components

The pbuffer attribute EGL_TEXTURE_FORMAT determines the base internal format of the texture. The component sizes are also determined by pbuffer attributes as shown in table 3.6: The texture target is derived from the EGL_TEXTURE_TARGET attribute of surface. If the attribute value is EGL_TEXTURE_2D, then buffer defines a texture for the two-dimensional texture object which is bound to the current context (hereafter referred to as the current texture object). If dpy and surface are the display and surface for the calling thread’s current context, eglBindTexImage performs an implicit glFlush. For other surfaces, eglBindTexImage waits for all effects from previously issued client API commands drawing to the surface to complete before defining the texture image, as though glFinish were called on the last context to which that surface were bound. After eglBindTexImage is called, the specified surface is no longer available for reading or writing. Any read operation, such as glReadPixels or eglCopyBuffers, which reads values from any of the surface’s color buffers or ancillary buffers will produce indeterminate results. In addition, draw operations that are done to the surface before its color buffer is released from the texture produce indeterminate results. Specifically, if the surface is current to a context and thread then rendering commands will be processed and the context state will be updated, but the surface may or may not be written. eglSwapBuffers has no effect if it is called on a bound surface. Client APIs other than OpenGL ES may be used to render into a surface later bound as a texture. The effects of binding a surface as an OpenGL ES texture when the surface is current to a client API context other than OpenGL ES are generally similar those described above, but there may be additional restrictions. Applications using mixed-mode render-to-texture in this fashion should unbind surfaces from all client API contexts before binding those surfaces as OpenGL ES textures. Note that the color buffer is bound to a texture object. If the texture object is shared between contexts, then the color buffer is also shared. If a texture object is deleted before eglReleaseTexImage is called, then the color buffer is released and

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3.6. RENDERING TO TEXTURES

the surface is made available for reading and writing. Texture mipmap levels are automatically generated when all of the following conditions are met while calling eglBindTexImage: • The EGL_MIPMAP_TEXTURE attribute of the pbuffer being bound is EGL_TRUE. • The OpenGL ES texture parameter GL_GENERATE_MIPMAP is GL_TRUE for the currently bound texture. • The value of the EGL_MIPMAP_LEVEL attribute of the pbuffer being bound is equal to the value of the texture parameter GL_TEXTURE_BASE_LEVEL. In this case, additional mipmap levels are generated as described in section 3.8 of the OpenGL ES 1.1 Specification. It is not an error to call glTexImage2D or glCopyTexImage2D to replace an image of a texture object that has a color buffer bound to it. However, these calls will cause the color buffer to be released back to the surface and new memory will be allocated for the texture. Note that the color buffer is released even if the image that is being defined is a mipmap level that was not defined by the color buffer. Errors eglBindTexImage returns EGL_FALSE on failure. If eglBindTexImage is called and the surface attribute EGL_TEXTURE_FORMAT is set to EGL_NO_TEXTURE, then an EGL_BAD_MATCH error is returned. If buffer is already bound to a texture then an EGL_BAD_ACCESS error is returned. If buffer is not a valid buffer, then an EGL_BAD_PARAMETER error is generated. If surface is not a valid EGLSurface, or is not a pbuffer surface supporting texture binding, then an EGL_BAD_SURFACE error is generated. eglBindTexImage is ignored if there is no current rendering context.

3.6.2

Releasing a Surface from an OpenGL ES Texture

To release a color buffer that is being used as a texture, call EGLBoolean eglReleaseTexImage(EGLDisplay dpy, EGLSurface surface, EGLint buffer); EGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS

The specified color buffer is released back to the surface. The surface is made available for reading and writing when it no longer has any color buffers bound as textures. The contents of the color buffer are undefined when it is first released. In particular, there is no guarantee that the texture image is still present. However, the contents of other color buffers are unaffected by this call. Also, the contents of the depth and stencil buffers are not affected by eglBindTexImage and eglReleaseTexImage. If the specified color buffer is no longer bound to a texture (e.g., because the texture object was deleted) then eglReleaseTexImage has no effect. No error is generated. After a color buffer is released from a texture (either explicitly by calling eglReleaseTexImage or implicitly by calling a routine such as glTexImage2D), all texture images that were defined by the color buffer become NULL (it is as if glTexImage was called with an image of zero width). Errors If eglReleaseTexImage is called and the value of surface attribute EGL_TEXTURE_FORMAT is EGL_NO_TEXTURE, then an EGL_BAD_MATCH error is returned. If buffer is not a valid buffer (currently only EGL_BACK_BUFFER may be specified), then an EGL_BAD_PARAMETER error is generated. If surface is not a valid EGLSurface, or is not a bound pbuffer surface, then an EGL_BAD_SURFACE error is returned.

3.6.3

Implementation Caveats

Developers should note that conformant OpenGL ES implementations are not required to support render to texture; that is, there may be no EGLConfigs supporting the EGL_BIND_TO_TEXTURE_RGB or EGL_BIND_TO_TEXTURE_RGBA attributes. Render to texture is functionally subsumed by the newer framebuffer object extension to OpenGL ES, and may eventually be deprecated. Render to texture is not supported for OpenGL contexts.

3.7

Rendering Contexts

EGL provides functions to create and destroy rendering contexts for each supported client API; to query information about rendering contexts; and to bind rendering EGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS

contexts to surfaces, making them current. At most one context for each supported client API may be current to a particular thread at a given time, and at most one context may be bound to a particular surface at a given time13 . The minimum number of current contexts that must be supported by an EGL implementation is one for each supported client API14 . Only one OpenGL or OpenGL ES context may be current to a particular thread, even if the implementation supports OpenGL and one or more versions of OpenGL ES in the same runtime15 . This restriction is enforced by eglMakeCurrent as described in section 3.7.3. Some of the functions described in this section make use of the current rendering API, which is set on a per-thread basis16 by calling EGLBoolean eglBindAPI(EGLenum api); api must specify one of the supported client APIs, either EGL_OPENGL_API, EGL_OPENGL_ES_API, or EGL_OPENVG_API. Applications using multiple client APIs are responsible for ensuring the current rendering API is correct before calling the functions eglCreateContext, eglGetCurrentContext, eglGetCurrentDisplay, eglGetCurrentSurface, eglCopyBuffers, eglSwapBuffers, eglSwapInterval, eglMakeCurrent (when its ctx parameter is EGL_NO_CONTEXT), eglWaitClient, or eglWaitNative. EGL_OPENGL_API and EGL_OPENGL_ES_API are interchangeable for all purposes except eglCreateContext17 . 13 Note that this implies that implementations must allow (for example) both an OpenGL ES and an OpenVG context to be current to the same thread, so long as they are drawing to different surfaces. 14 This constraint allows valid implementations which are restricted to supporting only one active rendering thread in a thread group. Such implementations may generate errors in eglMakeCurrent. 15 This restriction is necessary because many entry points are shared by OpenGL and both versions of OpenGL ES. Determining which library version to call into is based on properties of the current OpenGL or OpenGL ES context. 16 Note that the current rendering API is set on a per-thread basis, but not on a per-EGLDisplay basis. This is because current contexts are bound in the same manner. 17 This is a behavior change introduced in the February, 2013 EGL 1.4 specification update. Prior to this change, operations such as (for example) calling eglGetCurrentContext when an OpenGL ES context is current but the current rendering API is EGL_OPENGL_API would return EGL_NO_CONTEXT instead of the OpenGL ES context. The change is subtle, unlikely to affect any existing applications, and intended as a convenience to the programmer. It is based on the restriction described above (that only one OpenGL or OpenGL ES context may be current to a particular thread). It is still necessary to distinguish between the two current rendering APIs when creating a context on an implementation which supports both OpenGL and OpenGL ES.

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3.7. RENDERING CONTEXTS

Errors eglBindAPI returns EGL_FALSE on failure. If api is not one of the values specified above, or if the client API specified by api is not supported by the implementation, an EGL_BAD_PARAMETER error is generated. To obtain the value of the current rendering API, call EGLenum eglQueryAPI(void); The value returned will be one of the valid api parameters to eglBindAPI, or EGL_NONE.

The initial value of the current rendering API is EGL_OPENGL_ES_API, unless OpenGL ES is not supported by an implementation, in which case the initial value is EGL_NONE.

3.7.1

Creating Rendering Contexts

To create a rendering context for the current rendering API, call EGLContext eglCreateContext(EGLDisplay dpy, EGLConfig config, EGLContext share_context, const EGLint *attrib_list); If eglCreateContext succeeds, it initializes the context to the initial state defined for the current rendering API, and returns a handle to it. The context can be used to render to any compatible EGLSurface. Although contexts are specific to a single client API, all contexts created in EGL exist in a single namespace. This allows many EGL calls which manage contexts to avoid use of the current rendering API. If share context is not EGL_NO_CONTEXT, then all shareable data, as defined by the client API (note that for OpenGL and OpenGL ES, shareable data excludes texture objects named 0) will be shared by share context, all other contexts share context already shares with, and the newly created context. An arbitrary number of EGLContexts can share data in this fashion. The OpenGL and OpenGL ES server context state for all sharing contexts must exist in a single address space. attrib list specifies a list of attributes for the context. The list has the same structure as described for eglChooseConfig. If an attribute is not specified in attrib list, then the default value specified below is used instead. Most attributes are only meaningful for specific client APIs, and will generate an error when specified for other types of contexts. EGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS 3.7.1.1

OpenGL and OpenGL ES Context Versions

The values for attributes EGL_CONTEXT_MAJOR_VERSION and EGL_CONTEXT_MINOR_VERSION specify the requested client API version. They are only meaningful for OpenGL and OpenGL ES contexts, and specifying them for other types of contexts will generate an error. When the current rendering API is EGL_OPENGL_ES_API or EGL_OPENGL_API, the values of EGL_CONTEXT_MAJOR_VERSION18 (the major version) and EGL_CONTEXT_MINOR_VERSION (the minor version) request creation of an OpenGL ES or OpenGL context, respectively, supporting the specified version major.minor of that client API. The context returned must be the specified version, or a later version which is backwards compatible with that version. Even if a later version is returned, the specified version must correspond to a defined version of the client API. Defined versions and backwards compatibility are determined as follows: For an OpenGL ES context: • Defined versions are 1.0, 1.1, 2.0, 3.0, and any later versions of OpenGL ES released by Khronos. • If version 1.0 is requested, the context returned may implement either OpenGL ES 1.0 or OpenGL ES 1.1. • If version 1.1 is requested, the context returned must implement OpenGL ES 1.1. • If version 2.0, version 3.0, or a later version (when later versions are defined by Khronos) is requested, the context returned must implement the requested OpenGL ES version, or any later version which is backwards compatible with the requested version. For an OpenGL context: • Defined versions are 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 2.0, 2.1, 3.0, 3.1, 3.2, 4.0, 4.1, 4.2, 4.3, 4.4, and any later versions of OpenGL released by Khronos. • If a version less than or equal to OpenGL 3.0 is requested, the context returned may implement any of the following versions: – Any version no less than that requested and no greater than 3.0. 18

The EGL 1.4 token EGL_CONTEXT_CLIENT_VERSION is an alias for EGL_CONTEXT_MAJOR_VERSION, and the tokens may be used interchangeably.

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3.7. RENDERING CONTEXTS

– Version 3.1, if the GL_ARB_compatibility extension is also implemented. – The compatibility profile of version 3.2 or greater. • If OpenGL 3.1 is requested, the context returned may implement any of the following versions: – Version 3.1. The GL_ARB_compatibility extension may or may not be implemented, as determined by the implementation. – The core profile of version 3.2 or greater. • If OpenGL 3.2 or greater is requested, the context returned may implement any of the following versions: – The requested profile (see attribute EGL_CONTEXT_OPENGL_PROFILE_MASK below) of the requested version. – The requested profile of any later version, so long as no features have been removed from that later version and profile. Typically, the implementation will return the most recent version of OpenGL it supports which is backwards compatible with the requested version. Querying the GL_VERSION string with glGetString in either OpenGL or OpenGL ES (or the GL_MAJOR_VERSION and GL_MINOR_VERSION values with glGetIntegerv, in an OpenGL 3.0 or later context) will return the actual version supported by a context. The default values for EGL_CONTEXT_MAJOR_VERSION and EGL_CONTEXT_MINOR_VERSION are 1 and 0 respectively. 3.7.1.2

OpenGL Context Profiles

The value for attribute EGL_CONTEXT_OPENGL_PROFILE_MASK specifies a profile of the OpenGL API. This attribute is only meaningful for OpenGL contexts, and specifying it for other types of contexts, including OpenGL ES contexts, is an error. When the current rendering API is EGL_OPENGL_API, the value of EGL_CONTEXT_OPENGL_PROFILE_MASK requests an OpenGL context supporting the corresponding profile. If the EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT bit is set in the attribute value, then a context implementing the core profile of OpenGL is returned. If the EGL_CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT bit is set, then a context implementing the compatibility profile is returned. If the EGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS

requested OpenGL version is less than 3.2, EGL_CONTEXT_OPENGL_PROFILE_MASK is ignored and the functionality of the context is determined solely by the requested version. Querying the value of GL_CONTEXT_PROFILE_MASK with glGetIntegerv will return the profile mask used to create the context. This query is only supported in an OpenGL 3.2 or later context. The default value for EGL_CONTEXT_OPENGL_PROFILE_MASK is EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT. All OpenGL 3.2 and later implementations are required to implement the core profile, but implementation of the compatibility profile is optional. If the core profile is requested, then the context returned cannot implement functionality defined only by the compatibility profile. 3.7.1.3

OpenGL and OpenGL ES Debug Contexts

If the EGL_CONTEXT_OPENGL_DEBUG attribute is set to EGL_TRUE, a debug context will be created. Debug contexts are intended for use during application development, to provide additional runtime checking, validation, and logging functionality while possibly incurring performance penalties. OpenGL and OpenGL ES implementations supporting the GL_KHR_debug extension, or equivalent core API functionality, are required to enable it when creating a debug context. Additional debug context functionality, if any, is determined by the implementation. This attribute is supported only for OpenGL and OpenGL ES contexts. If the implementaton does not support any additional debug functionality, context creation will not fail, but the resulting context will be identical to a non-debug context. The default value for EGL_CONTEXT_OPENGL_DEBUG is EGL_FALSE. 3.7.1.4

OpenGL Forward Compatible Contexts

If the EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE attribute is set to EGL_TRUE, a forward-compatible context will be created. Forward-compatible contexts are defined only for OpenGL versions 3.0 and later. They must not support functionality marked as deprecated by that version of the API, while a non-forwardcompatible context must support all functionality in that version, deprecated or not. This attribute is supported only for OpenGL contexts. If a forward-compatible context is requested for OpenGL versions less than 3.0, or the implementation does not support forward-compatible contexts for later versions, context creation will fail. The default value for EGL_CONTEXT_FORWARD_COMPATIBLE is EGL_FALSE.

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3.7. RENDERING CONTEXTS 3.7.1.5

OpenGL and OpenGL ES Robust Buffer Access

If the EGL_CONTEXT_OPENGL_ROBUST_ACCESS attribute is set to EGL_TRUE, a context supporting robust buffer access will be created. OpenGL contexts must support the GL_ARB_robustness extension, or equivalent core API functionality. OpenGL ES contexts must support the GL_EXT_robustness extension, or equivalent core API functionality. This attribute is supported only for OpenGL and OpenGL ES contexts. If the implementation does not support robust buffer access, context creation will fail. The default value of EGL_CONTEXT_OPENGL_ROBUST_ACCESS is EGL_FALSE. 3.7.1.6

OpenGL and OpenGL ES Reset Notification Strategy

The attribute EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY specifies reset notification behavior for a context supporting robust buffer access. The attribute value may be either EGL_NO_RESET_NOTIFICATION or EGL_LOSE_CONTEXT_ON_RESET, which respectively result in reset notification behavior of GL_NO_RESET_NOTIFICATION_ARB and GL_LOSE_CONTEXT_ON_RESET_ARB, as described by the OpenGLGL_ARB_robustness extension, or by equivalent functionality19 . This attribute is supported only for OpenGL and OpenGL ES contexts. If the EGL_CONTEXT_OPENGL_ROBUST_ACCESS attribute is not set to EGL_TRUE, context creation will not fail, but the resulting context may not support robust buffer access, and therefore may not support the requested reset notification strategy The default value for EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY is EGL_NO_RESET_NOTIFICATION. Errors On failure eglCreateContext returns EGL_NO_CONTEXT. An EGL_BAD_MATCH error is generated if the current rendering api is EGL_NONE (this situation can only arise in an implementation which does not support OpenGL ES 1.x, and prior to the first call to eglBindAPI). An EGL_BAD_ATTRIBUTE error is generated if an attribute is specified that is not supported for the client API type determined by the current rendering API. An EGL_BAD_ATTRIBUTE error is generated if an attribute name or at19

An example of equivalent functionality for OpenGL ES is the vendor GL_EXT_-

robustness extension.

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3.7. RENDERING CONTEXTS

tribute value in attrib list is not recognized (including undefined or unsupported bits in bitmask attributes), An EGL_BAD_CONTEXT error is generated if share context is neither EGL_NO_CONTEXT nor a valid context of the same client API type as the newly created context. An EGL_BAD_CONFIG error is generated if config is not a valid EGLConfig. An EGL_BAD_MATCH error is generated if config does not support the requested client API. This includes requesting creation of an OpenGL ES 1.x, 2.0, or 3.0 context when the EGL_RENDERABLE_TYPE attribute of config does not contain EGL_OPENGL_ES_BIT, EGL_OPENGL_ES2_BIT, or EGL_OPENGL_ES3_BIT respectively. An EGL_BAD_MATCH error is generated if an OpenGL or OpenGL ES context is requested and any of: • the server context state for share context exists in an address space that cannot be shared with the newly created context • share context was created on a different display than the one referenced by config • the reset notification behavior of share context and the newly created context are different • the contexts are otherwise incompatible (for example, one context being associated with a hardware device driver and the other with a software renderer). An EGL_BAD_MATCH error is generated if an OpenGL or OpenGL ES context is requested and the specified version number is not a defined version of that client API. An EGL_BAD_MATCH error is generated if an forward-compatible OpenGL context is requested and the requested OpenGL version is less than 3.0, or the implementation does not support a forward-compatible context of exactly the requested version. Because the purpose of forward-compatible contexts is to allow application development on a specific OpenGL version with the knowledge that the app will run on a future version, in this case context creation cannot result in a later, backwards-compatible version. An EGL_BAD_MATCH error is generated if an OpenGL or OpenGL ES context is requested with robust buffer access, and the implementation does not support the corresponding OpenGL or OpenGL ES extension. An EGL_BAD_MATCH error is generated if an OpenGL or OpenGL ES context is requested with robust buffer access and with a specified reset notificaEGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS

tion behavior, and the implementation does not support that behavior. An EGL_BAD_MATCH error is generated if an OpenGL context is requested, the requested version is 3.2 or greater, and any of: • the context profile mask has no bits set • the mask has any bits set other than EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT and EGL_CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT

• the mask has more than one of these bits set • the implementation does not support the requested profile. An EGL_BAD_MATCH error is generated if config does not support a context compatible with the requested API version and context attributes for reasons not enumerated above. It is difficult to enumerate all possible combinations of unsupported context version attributes, since this sometimes depends on properties of the implementation; this error allows such implementations to indicate they cannot satisfy a request. If the server does not have enough resources to allocate the new context, then an EGL_BAD_ALLOC error is generated.

3.7.2

Destroying Rendering Contexts

A rendering context is destroyed by calling EGLBoolean eglDestroyContext(EGLDisplay dpy, EGLContext ctx); All resources associated with ctx are marked for deletion as soon as possible. When multiple contexts share objects (see eglCreateContext), such shared objects are not deleted until after all contexts on the share list are destroyed, unless the objects are first explicitly deleted by the application. Following eglDestroyContext, the context and the handle referring to it are treated in the same fashion as a context destroyed by eglTerminate (see section 3.2). Errors eglDestroyContext returns EGL_FALSE on failure. An EGL_BAD_CONTEXT error is generated if ctx is not a valid context.

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3.7. RENDERING CONTEXTS

3.7.3

Binding Contexts and Drawables

To make a context current, call EGLBoolean eglMakeCurrent(EGLDisplay dpy, EGLSurface draw, EGLSurface read, EGLContext ctx); eglMakeCurrent binds ctx to the current rendering thread and to the draw and read surfaces. For an OpenGL or OpenGL ES context, draw is used for all operations except for any pixel data read back or copied, which is taken from the frame buffer values of read. Note that the same EGLSurface may be specified for both draw and read. For an OpenVG context, the same EGLSurface must be specified for both draw and read. If the calling thread already has a current context of the same client API type as ctx, then that context is flushed and marked as no longer current. ctx is then made the current context for the calling thread. For purposes of eglMakeCurrent, the client API type of all OpenGL ES and OpenGL contexts is considered the same. In other words, if any OpenGL ES context is currently bound and ctx is an OpenGL context, or if any OpenGL context is currently bound and ctx is an OpenGL ES context, the currently bound context will be made no longer current and ctx will be made current. OpenGL and OpenGL ES buffer mappings created by e.g. glMapBuffer are not affected by eglMakeCurrent; they persist whether the context owning the buffer is current or not. Errors eglMakeCurrent returns EGL_FALSE on failure. If draw or read are not compatible with ctx, then an EGL_BAD_MATCH error is generated. If ctx is current to some other thread, or if either draw or read are bound to contexts in another thread, an EGL_BAD_ACCESS error is generated. If binding ctx would exceed the number of current contexts of that client API type supported by the implementation, an EGL_BAD_ACCESS error is generated. If either draw or read are pbuffers created with eglCreatePbufferFromClientBuffer, and the underlying bound client API buffers are in use by the client API that created them, an EGL_BAD_ACCESS error is generated. EGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS

If ctx is not a valid context and is not EGL_NO_CONTEXT, an EGL_BAD_CONTEXT error is generated.

If either draw or read are not valid EGL surfaces and are not EGL_NO_SURFACE, an EGL_BAD_SURFACE error is generated. If ctx is EGL_NO_CONTEXT and either draw or read are not EGL_NO_SURFACE, an EGL_BAD_MATCH error is generated. If either of draw or read is a valid surface and the other is EGL_NO_SURFACE, an EGL_BAD_MATCH error is generated. If ctx does not support being bound without read and draw surfaces, and both draw and read are EGL_NO_SURFACE, an EGL_BAD_MATCH error is generated. If a native window underlying either draw or read is no longer valid, an EGL_BAD_NATIVE_WINDOW error is generated. If draw and read cannot fit into graphics memory simultaneously, an EGL_BAD_MATCH error is generated. If the previous context of the calling thread has unflushed commands, and the previous surface is no longer valid, an EGL_BAD_CURRENT_SURFACE error is generated. If the ancillary buffers for draw and read cannot be allocated, an EGL_BAD_ALLOC error is generated. If a power management event has occurred, an EGL_CONTEXT_LOST error is generated. As with other commands taking EGLDisplay parameters, if dpy is not a valid EGLDisplay handle, an EGL_BAD_DISPLAY error is generateda . Other errors may arise when the context state is inconsistent with the surface state, as described in the following paragraphs. a

Some implementations have chosen to allow EGL_NO_DISPLAY as a valid dpy parameter for eglMakeCurrent. This behavior is not portable to all EGL implementations, and should be considered as an undocumented vendor extension.

If draw is destroyed after eglMakeCurrent is called, then subsequent rendering commands will be processed and the context state will be updated, but the surface contents become undefined. If read is destroyed after eglMakeCurrent then pixel values read from the framebuffer (e.g., as result of calling glReadPixels) are undefined. If a native window or pixmap underlying the draw or read surfaces is destroyed, rendering and readback are handled as above. To release the current context without assigning a new one, set ctx to EGL_NO_CONTEXT and set draw and read to EGL_NO_SURFACE. The currently bound context for the client API specified by the current rendering API is flushed and marked as no longer current, and there will be no current context for that client API EGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS

after eglMakeCurrent returns. This is the only case in which eglMakeCurrent respects the current rendering API. In all other cases, the client API affected is determined by ctx. This is the only case where an uninitialized display may be passed to eglMakeCurrent. If any of the following are true: • ctx is not EGL_NO_CONTEXT • read is not EGL_NO_SURFACE • draw is not EGL_NO_SURFACE then an EGL_NOT_INITIALIZED error is generated if dpy is a valid but uninitialized display. If ctx is EGL_NO_CONTEXT, then draw and read must be EGL_NO_SURFACE. If ctx is not EGL_NO_CONTEXT, then both draw and read must not be EGL_NO_SURFACE unless ctx is a context which supports being bound without read and draw surfaces. In this case the context is made current without a default framebuffer. The meaning of this is defined by the client API of the supporting context (see chapter 4 of the OpenGL 3.0 Specification, and the GL_OES_surfaceless_context OpenGL ES extension.). The first time a OpenGL or OpenGL ES context is made current the viewport and scissor dimensions are set to the size of the draw surface (as though glViewport(0,0,w,h) and glScissor(0,0,w,h) were called, where w and h are the width and height of the surface, respectively). However, the viewport and scissor dimensions are not modified when ctx is subsequently made current. The client is responsible for resetting the viewport and scissor in this case. The first time ctx is made current, if it is without a default framebuffer (e.g. both draw and read are EGL_NO_SURFACE), then the viewport and scissor regions are set as though glViewport(0,0,0,0) and glScissor(0,0,0,0) were called. Implementations may delay allocation of auxiliary buffers for a surface until they are required by a context (which may result in the EGL_BAD_ALLOC error described above). Once allocated, however, auxiliary buffers and their contents persist until a surface is deleted. 3.7.3.1

Multisample Buffers and Multiple Rendering Streams

When rendering to a surface containing multisample buffers (created with respect to an EGLConfig whose EGL_SAMPLE_BUFFERS attribute has a value of one), switching rendering between client APIs may force resolution of the multisample buffer into the color buffer. This can occur for many reasons, such as client EGL 1.5 - August 27, 2014

3.7. RENDERING CONTEXTS

APIs which do not share the same interpretation of the multisample information (for example, using different sample locations or weightings); client APIs which do not support multisample rendering; or applications which enable multisample rendering in one client API and disable it in another. Repeated resolution of the multisample buffer may result in lower quality images. For this reason, applications mixing rendering by multiple client APIs onto the same surface should minimize switching between client APIs. Ideally, each client API rendering to a surface should be made current only once for each frame being rendered. 3.7.3.2

Order of Rendering Operations Between Contexts

EGL makes no guarantees on the rendering order between contexts, even within the same thread. For example, rendering operations performed by a thread while one context is current do not necessarily complete before rendering operations performed later in the same thread but with a different context current. It is the responsibility of the application to employ the correct synchronization when the drawing result of one context needs to be complete before another context accesses that result. Otherwise the result is undefined. To achieve synchronization, an application can use client API-specific commands such as glFinish to wait for rendering operations to complete in one context before making the next current. Alternatively, synchronization objects can be used to order rendering operations between contexts, if supported by the underlying implementation. Synchronization objects are defined by the EGL_KHR_fence_sync and EGL_KHR_wait_sync EGL extensions, or alternatively, they may be available as a feature of the underlying client API. Use of synchronization objects may allow asynchronous execution of the rendering operations, achieving better performance than synchronous wait functions like glFinish.

3.7.4

Context Queries

Several queries exist to return information about contexts. To get the current context for the current rendering API, call EGLContext eglGetCurrentContext(void); If there is no current context for the current rendering API, or if the current rendering API is EGL_NONE, then EGL_NO_CONTEXT is returned (this is not an error). If the current context has been marked for deletion as a result of calling eglTerminate or eglDestroyContext, the handle returned by eglGetCurrentContext is not

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3.7. RENDERING CONTEXTS

valid, and cannot be passed successfully to any other EGL function, as discussed in section 3.2. To get the surfaces used for rendering by a current context, call EGLSurface eglGetCurrentSurface(EGLint readdraw); readdraw is either EGL_READ or EGL_DRAW, to return respectively the read or draw surfaces bound to the current context in the calling thread, for the current rendering API. If there is no current context for the current rendering API, then EGL_NO_SURFACE is returned (this is not an error). Errors eglGetCurrentContext returns EGL_NO_SURFACE on failure (but may also return it if no context is bound, as described above) If readdraw is neither EGL_READ nor EGL_DRAW, an EGL_BAD_PARAMETER error is generated. If a current surface has been marked for deletion as a result of calling eglTerminate or eglDestroySurface, the handle returned by eglGetCurrentSurface is not valid, and cannot be passed successfully to any other EGL function, as discussed in section 3.2. To get the display associated with a current context, call EGLDisplay eglGetCurrentDisplay(void); The display for the current context in the calling thread, for the current rendering API, is returned. If there is no current context for the current rendering API, EGL_NO_DISPLAY is returned (this is not an error). Note that EGL_NO_DISPLAY is used solely to represent an error condition, and is not a valid EGLDisplay handle. Errors Passing EGL_NO_DISPLAY to any command taking an EGLDisplay parameter will generate either an EGL_BAD_DISPLAY error if the EGL implementation validates EGLDisplay handles, or undefined behavior as described at the end of section 3.1. The only exception to this rule is that eglQueryString will accept an EGLDisplay parameter of EGL_NO_DISPLAY

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3.7. RENDERING CONTEXTS

when querying the client extension string (see section 3.3). To obtain the value of context attributes, use EGLBoolean eglQueryContext(EGLDisplay dpy, EGLContext ctx, EGLint attribute, EGLint *value); eglQueryContext returns in value the value of attribute for ctx. attribute must be set to EGL_CONFIG_ID, EGL_CONTEXT_CLIENT_TYPE, EGL_CONTEXT_CLIENT_VERSION, or EGL_RENDER_BUFFER. Querying EGL_CONFIG_ID returns the ID of the EGLConfig with respect to which the context was created. Querying EGL_CONTEXT_CLIENT_TYPE returns the type of client API this context supports (the value of the api parameter to eglBindAPI). Querying EGL_CONTEXT_CLIENT_VERSION returns the version of the client API this context actually supports (which may differ from the version specified at context creation time). The resulting value is only meaningful for an OpenGL ES context. Querying EGL_RENDER_BUFFER returns the buffer which client API rendering via this context will use. The value returned depends on properties of both the context, and the draw surface to which the context is bound: • If the context is bound to a pixmap surface, then EGL_SINGLE_BUFFER will be returned. • If the context is bound to a pbuffer surface, then EGL_BACK_BUFFER will be returned. • If the context is bound to a window surface, then either EGL_BACK_BUFFER or EGL_SINGLE_BUFFER may be returned. The value returned depends on both the buffer requested by the setting of the EGL_RENDER_BUFFER property of the surface (which may be queried by calling eglQuerySurface - see section 3.5.6), and on the client API (not all client APIs support single-buffer rendering to window surfaces). Some client APIs allow control of whether rendering goes to the front or back buffer. This client API-specific choice is not reflected in the returned value, which only describes the buffer that will be rendered to by default if not overridden by the client API. • If the context is not bound to a surface, then EGL_NONE will be returned.

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3.8. SYNCHRONIZATION PRIMITIVES

Errors eglQueryContext returns EGL_FALSE on failure and value is not updated. If attribute is not a valid EGL context attribute, then an EGL_BAD_ATTRIBUTE error is generated. If ctx is invalid, an EGL_BAD_CONTEXT error is generated.

3.8

Synchronization Primitives

To prevent native rendering API functions from executing until any outstanding client API rendering affecting the same surface is complete, call EGLBoolean eglWaitClient(void); All rendering calls for the currently bound context, for the current rendering API, made prior to eglWaitClient, are guaranteed to be executed before native rendering calls made after eglWaitClient which affect the read or draw surfaces associated with that context. The same result can be achieved using client API-specific calls such as glFinish or vgFinish. Clients rendering to single buffered surfaces (e.g. pixmap surfaces) should call eglWaitClient before accessing the native pixmap from the client. eglWaitClient returns EGL_TRUE on success. If there is no current context for the current rendering API, the function has no effect but still returns EGL_TRUE. Errors eglWaitClient returns EGL_FALSE on failure. If a surface associated with the calling thread’s current context is no longer valid, an EGL_BAD_CURRENT_SURFACE error is generated. For backwards compatibility, the function EGLBoolean eglWaitGL(void); is equivalent to EGLenum api = eglQueryAPI(); eglBindAPI(EGL_OPENGL_ES_API); eglWaitClient(); EGL 1.5 - August 27, 2014

3.8. SYNCHRONIZATION PRIMITIVES

eglBindAPI(api); To prevent a client API command sequence from executing until any outstanding native rendering affecting the same surface is complete, call EGLBoolean eglWaitNative(EGLint engine); Native rendering calls made with the specified marking engine, and which affect the read or draw surfaces associated with the calling thread’s current context, for the current rendering API, are guaranteed to be executed before client API rendering calls made after eglWaitNative. The same result may be (but is not necessarily) achievable using native synchronization calls. engine denotes a particular marking engine (another drawing API, such as GDI or Xlib) to be waited on. Valid values of engine are defined by EGL extensions specific to implementations, but implementations will always recognize the symbolic constant EGL_CORE_NATIVE_ENGINE, which denotes the most commonly used marking engine other then a client API. eglWaitNative returns EGL_TRUE on success. If there is no current context, the function has no effect but still returns EGL_TRUE. If a surface does not support native rendering (e.g. pbuffer and in most cases window surfaces), the function has no effect but still returns EGL_TRUE. Errors eglWaitNative returns EGL_FALSE on failure. If the surface associated with the calling thread’s current context is no longer valid, an EGL_BAD_CURRENT_SURFACE error is generated. If engine does not denote a recognized marking engine, an EGL_BAD_PARAMETER error is generated.

3.8.1

Sync Objects

In addition to the aforementioned synchronization functions, which provide an efficient means of serializing client and native API operations within a thread, sync objects are provided to enable synchronization of client API operations between threads and/or between API contexts. Sync objects may be tested or waited upon by application threads. Sync objects have a status with two possible states: signaled and unsignaled. Initially, sync objects are unsignaled. EGL may be asked to wait for a sync object to become signaled, or a sync object’s status may be queried. EGL 1.5 - August 27, 2014

3.8. SYNCHRONIZATION PRIMITIVES

Depending on the type of a sync object, its status may be changed either by an external event, or by explicitly signaling and unsignaling the sync. Sync objects are associated with an EGLDisplay when they are created, and have attributes defining additional aspects of the sync object. All sync objects include attributes for their type and their status. Additional attributes are discussed below for different types of sync objects. Fence sync objects are created in association with a fence command in a client API. When the client API executes the fence command, an event is generated which signals the corresponding fence sync object. Fence sync objects may not be explicitly signaled, and may only change their status once, from the initial unsignaled status to signaled. Fence sync objects may be used to wait for partial completion of a client API command stream, as a more flexible form of glFinish or vgFinish. A OpenCL event sync object reflects the status of a corresponding OpenCL event object to which the sync object is linked. This provides another method of coordinating sharing of images between EGL and OpenCL (see Chapter 9 of the OpenCL 1.0 Specification and the cl_khr_egl_image extension). Waiting on such a sync object is equivalent to waiting for completion of the linked OpenCL event object. The command EGLSync eglCreateSync(EGLDisplay dpy, EGLenum type, const EGLAttrib *attrib_list); creates a sync object of the specified type associated with the specified display dpy, and returns a handle to the new object. attrib list is an attribute-value list specifying other attributes of the sync object, terminated by an attribute entry EGL_NONE. Attributes not specified in the list will be assigned their default values. Once the condition of the sync object is satisfied, the sync is signaled, causing any eglClientWaitSync or eglWaitSync commands (see below) blocking on sync to unblock. 3.8.1.1

Creating Fence Sync Objects

If type is EGL_SYNC_FENCE, a fence sync object is created. In this case attrib list must be NULL or empty (containing only EGL_NONE). Attributes of the fence sync object are set as shown in table 3.7. When a fence sync object is created, eglCreateSync also inserts a fence command into the command stream of the bound client API’s current context (i.e., the context returned by eglGetCurrentContext), and associates it with the newly created sync object. EGL 1.5 - August 27, 2014

3.8. SYNCHRONIZATION PRIMITIVES Attribute Name

Initial Attribute Value(s)

EGL_SYNC_TYPE EGL_SYNC_STATUS EGL_SYNC_CONDITION

EGL_SYNC_FENCE EGL_UNSIGNALED EGL_SYNC_PRIOR_COMMANDS_COMPLETE

Table 3.7: Fence sync attributes and initial values.

The only condition supported for fence sync objects is EGL_SYNC_PRIOR_COMMANDS_COMPLETE, which is satisfied by completion of the fence command corresponding to the sync object, and all preceding commands in the associated client API context’s command stream. The sync object will not be signaled until all effects from these commands on the client API’s internal and framebuffer state are fully realized. No other state is affected by execution of the fence command. Creation of fence sync objects requires support from the bound client API, and will not succeed unless the client API satisfies one of the following properties. Note that eglWaitSync (see section 3.8.1.3) also requires satisfying these conditions. • client API is OpenGL, and either the OpenGL version is 3.2 or greater, or the GL_ARB_sync extension is supported. • client API is OpenGL ES, and either the OpenGL ES version is 3.0 or greater, or the GL_OES_EGL_sync extension is supported. • client API is OpenVG, and the VG_KHR_EGL_sync extension is supported. 3.8.1.2

Creating OpenCL Event Sync Objects

If type is EGL_SYNC_CL_EVENT, an OpenCL event sync object is created. In this case attrib list must contain the attribute EGL_CL_EVENT_HANDLE, set to a valid OpenCL event handle returned by a call to clEnqueueReleaseGLObjects or clEnqueueReleaseEGLObjects; other types of OpenCL event handles are not supported. Note that EGL_CL_EVENT_HANDLE is not a queriable property of a sync object. Attributes of the OpenCL event sync object are set as shown in table 3.8. The status of such a sync object depends on event. When the status of event is CL_QUEUED, CL_SUBMITTED, or CL_RUNNING, the status of the linked sync object will be EGL_UNSIGNALED. When the status of event changes to CL_COMPLETE, the status of the linked sync object will become EGL_SIGNALED. The only condition supported for OpenCL event sync objects is EGL_SYNC_CL_EVENT_COMPLETE, which is satisfied when the status of the OpenCL event associated with the sync object changes to CL_COMPLETE. EGL 1.5 - August 27, 2014

3.8. SYNCHRONIZATION PRIMITIVES Attribute Name

Initial Attribute Value(s)

EGL_SYNC_TYPE EGL_SYNC_STATUS EGL_SYNC_CONDITION

Depends on status of event

EGL_SYNC_CL_EVENT EGL_SYNC_CL_EVENT_COMPLETE

Table 3.8: OpenCL event sync attributes and initial values.

Creating a linked sync object places a reference on the linked OpenCL event object. When the sync object is deleted, the reference will be removed from the event object. However, implementations are not required to validate the OpenCL event, and passing an invalid event handle in attrib list may result in undefined behavior up to and including program termination. Errors eglCreateSync returns EGL_NO_SYNC on failure. If dpy is not the name of a valid, initialized EGLDisplay, an EGL_BAD_DISPLAY error is generated. If attrib list contains an attribute name not defined for the type of sync object being created, an EGL_BAD_ATTRIBUTE error is generated. If type is not a supported type of sync object, an EGL_BAD_PARAMETER error is generated. If type is EGL_SYNC_FENCE and no context is current for the bound API (i.e., eglGetCurrentContext returns EGL_NO_CONTEXT), an EGL_BAD_MATCH error is generated. If type is EGL_SYNC_FENCE and dpy does not match the EGLDisplay of the currently bound context for the currently bound client API (the EGLDisplay returned by eglGetCurrentDisplay), an EGL_BAD_MATCH error is generated. If type is EGL_SYNC_FENCE and the current context for the currently bound client API does not support fence commands, an EGL_BAD_MATCH error is generated. If type is EGL_SYNC_CL_EVENT and EGL_CL_EVENT_HANDLE is not specified in attrib list, or its attribute value is not a valid OpenCL event handle as described above, then an EGL_BAD_ATTRIBUTE error is generated.

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3.8. SYNCHRONIZATION PRIMITIVES 3.8.1.3

Waiting For Sync Objects

The command EGLint eglClientWaitSync(EGLDisplay dpy, EGLSync sync, EGLint flags, EGLTime timeout); blocks the calling thread until the specified sync object sync is signaled, or until timeout nanoseconds have passed. More than one eglClientWaitSync may be outstanding on the same sync at any given time. When there are multiple threads blocked on the same sync and the sync object is signaled, all such threads are released, but the order in which they are released is not defined. If the value of timeout is zero, then eglClientWaitSync simply tests the current status of sync. If the value of timeout is the special value EGL_FOREVER, then eglClientWaitSync does not time out. For all other values, timeout is adjusted to the closest value allowed by the implementation-dependent timeout accuracy, which may be substantially longer than one nanosecond. eglClientWaitSync returns one of three status values describing the reason for returning. A return value of EGL_TIMEOUT_EXPIRED indicates that the specified timeout period expired before sync was signaled, or if timeout is zero, indicates that sync is not signaled. A return value of EGL_CONDITION_SATISFIED indicates that sync was signaled before the timeout expired, which includes the case when sync was already signaled when eglClientWaitSync was called. If an error occurs then an error is generated and EGL_FALSE is returned. If the sync object being blocked upon will not be signaled in finite time (for example, by an associated fence command issued previously, but not yet flushed to the graphics pipeline), then eglClientWaitSync may wait forever. To help prevent this behavior20 , if the EGL_SYNC_FLUSH_COMMANDS_BIT bit is set in flags, and sync is unsignaled when eglClientWaitSync is called, then the equivalent of Flush() will be performed for the current API context (i.e., the context returned by eglGetCurrentContext) before blocking on sync. If no context is current for the bound API, the EGL_SYNC_FLUSH_COMMANDS_BIT bit is ignored. Errors eglClientWaitSync returns EGL_FALSE on failure. 20 The simple Flush behavior defined by EGL_SYNC_FLUSH_COMMANDS_BIT will not help when waiting for a fence command issued in a different context’s command stream. Applications which block on a fence sync object must take additional steps to ensure that the context from which the associated fence command was issued has flushed that command to the graphics pipeline.

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3.8. SYNCHRONIZATION PRIMITIVES

If sync is not a valid sync object for dpy, an EGL_BAD_PARAMETER error is generated. If dpy does not match the EGLDisplay passed to eglCreateSync when sync was created, the behaviour is undefined. The command EGLBoolean eglWaitSync(EGLDisplay dpy, EGLSync sync, EGLint flags); is similar to eglClientWaitSync, but instead of blocking and not returning to the application until sync is signaled, eglWaitSync returns immediately. On success, EGL_TRUE is returned, and the server for the client API context21 will block until sync is signaled22 . sync has the same meaning as for eglClientWaitSync. flags must be 0. eglWaitSync requires support from the bound client API, and will not succeed unless the same client API properties described for creation of fence syncs in section 3.8.1.1 are satisfied. Errors eglWaitSync returns EGL_FALSE on failure, and does not cause the server for the client API context to block. If the current context for the currently bound client API does not support server waits, an EGL_BAD_MATCH error is generated. If no context is current for the currently bound client API (i.e., eglGetCurrentContext returns EGL_NO_CONTEXT), an EGL_BAD_MATCH error is generated. If dpy does not match the EGLDisplay passed to eglCreateSync when sync was created, the behavior is undefined. If sync is not a valid sync object for dpy, an EGL_BAD_PARAMETER error is generated. If flags is not 0, an EGL_BAD_PARAMETER error is generated. 21

The server may choose to wait either in the CPU executing server-side code, or in the GPU hardware if it supports this operation. 22 eglWaitSync allows applications to continue to queue commands from the application in anticipation of the sync being signaled, potentially increasing parallelism between application, client API server code, and the GPU. The server only blocks execution of commands for the specific context on which eglWaitSync was issued; other contexts implemented by the same server are not affected.

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3.8. SYNCHRONIZATION PRIMITIVES Attribute EGL_SYNC_TYPE EGL_SYNC_STATUS EGL_SYNC_CONDITION

Description Type of the sync object Status of the sync object Signaling condition

71 Supported Sync Objects All All EGL_SYNC_FENCE or EGL_SYNC_CL_EVENT

Table 3.9: Attributes accepted by eglGetSyncAttrib.

3.8.1.3.1 Multiple Waiters It is possible for the application thread calling a client API to be blocked on a sync object in a eglClientWaitSync command, the server for that client API context to be blocked as the result of a previous eglWaitSync command, and for additional eglWaitSync commands to be queued in the server, all for a single sync object. When the sync object is signaled in this situation, the client will be unblocked, the server will be unblocked, and all such queued eglWaitSync commands will continue immediately when they are reached. Sync objects may be waited on or signaled from multiple contexts of different client API types in multiple threads simultaneously, although some client APIs may not support eglWaitSync. This support is determined by client API-specific extensions. The command 3.8.1.4

Querying Sync Object Attributs

EGLBoolean eglGetSyncAttrib(EGLDisplay dpy, EGLSync sync, EGLint attribute, EGLAttrib *value); is used to query attributes of the sync object sync. Legal values for attribute depend on the type of sync object, as shown in table 3.9. Assuming no errors are generated, EGL_TRUE is returned and the value of the queried attribute is returned in *value. Errors On failure, eglGetSyncAttrib returns EGL_FALSE and *value is not modified. If sync is not a valid sync object for dpy, an EGL_BAD_PARAMETER error is generated. If attribute is not one of the attributes in table 3.9, an EGL_BAD_ATTRIBUTE error is generated. EGL 1.5 - August 27, 2014

3.9. EGLIMAGE SPECIFICATION AND MANAGEMENT

If attribute is not supported for the type of sync object passed in sync, an EGL_BAD_MATCH error is generated.

If dpy does not match the display passed to eglCreateSync when sync was created, behaviour is undefined. The command EGLBoolean eglDestroySync(EGLDisplay dpy, EGLSync sync); is used to destroy an existing sync object. If any eglClientWaitSync or eglWaitSync commands are blocking on sync when eglDestroySync is called, sync is flagged for deletion and will be deleted when the associated fence command or OpenCL event object has completed, and sync is no longer blocking any such egl*WaitSync command. Otherwise, the sync object is destroyed immediately. If no errors are generated, EGL_TRUE is returned, and sync will no longer be the handle of a valid sync object. Errors On failure, eglDestroySync returns EGL_FALSE. If sync is not a valid sync object for dpy, EGL_FALSE is returned and an EGL_BAD_PARAMETER error is generated. If dpy does not match the display passed to eglCreateSync when sync was created, the behaviour is undefined.

3.9

EGLImage Specification and Management

The command EGLImage eglCreateImage(EGLDisplay dpy, EGLContext ctx, EGLenum target, EGLClientBuffer buffer, const EGLAttrib *attrib_list); is used to create an EGLImage from an existing image resource buffer. dpy specifies the EGL display used for this operation. ctx specifies the EGL client API context used for this operation, or EGL_NO_CONTEXT if a client API context is not required. target specifies the type of resource being used as the EGLImage source EGL 1.5 - August 27, 2014

3.9. EGLIMAGE SPECIFICATION AND MANAGEMENT

(examples include two-dimensional textures in OpenGL ES contexts and VGImage objects in OpenVG contexts). buffer is the name (or handle) of a resource to be used as the EGLImage source, cast into the type EGLClientBuffer. attrib list is a list of attribute-value pairs which is used to select sub-sections of buffer for use as the EGLImage source, such as mipmap levels for OpenGL ES texture map resources, as well as behavioral options, such as whether to preserve pixel data during creation. If attrib list is non-NULL, the last attribute specified in the list must be EGL_NONE. The resource specified by dpy, ctx, target, buffer, and attrib list must not itself be an EGLImage sibling, or bound to a pbuffer EGLSurface resource (eglBindTexImage, eglCreatePbufferFromClientBuffer). Values accepted for target are shown in table 3.10. Attribute names accepted in attrib list are shown in table 3.11, together with the target for which each attribute name is valid, and the default value used for each attribute if it is not included in attrib list. eglCreateImage returns an EGLImage object corresponding to the image data specified by dpy, ctx, target, buffer and attrib list which may be referenced by client API operations. If target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_3D, EGL_GL_RENDERBUFFER, EGL_GL_TEXTURE_CUBE_MAP_POSITIVE_X, EGL_GL_TEXTURE_CUBE_MAP_NEGATIVE_X, EGL_GL_TEXTURE_CUBE_MAP_POSITIVE_Y, EGL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, EGL_GL_TEXTURE_CUBE_MAP_POSITIVE_Z, or EGL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, dpy must be a valid EGLDisplay, and ctx must be a valid OpenGL or OpenGL ES API context on that display. If target is EGL_GL_TEXTURE_2D, buffer must be the name of a nonzero, GL_TEXTURE_2D target texture object, cast into the type EGLClientBuffer. If target is one of the EGL_GL_TEXTURE_CUBE_MAP_* enumerants, buffer must be the name of a nonzero, GL_TEXTURE_CUBE_MAP (or equivalent in GL extensions) target texture object, cast into the type EGLClientBuffer. If target is EGL_GL_TEXTURE_3D, buffer must be the name of a nonzero, GL_TEXTURE_3D (or equivalent in GL extensions) target texture object, cast into the type EGLClientBuffer. attrib list should specify the mipmap level (EGL_GL_TEXTURE_LEVEL) and, where applicable, z-offset (EGL_GL_TEXTURE_ZOFFSET) which will be used as the EGLImage source; If not specified, the default values listed in table 3.11 will be used instead. Additional values specified in are ignored. There must exist some levels x and y such that the mipmap level requested lies between x and y (inclusive), the texture would be mipmap complete were x substituted for the base level and y substituted for the max level, and all levels less EGL 1.5 - August 27, 2014

3.9. EGLIMAGE SPECIFICATION AND MANAGEMENT

target EGL_GL_TEXTURE_2D EGL_GL_TEXTURE_CUBE_MAP_POSITIVE_X

EGL_GL_TEXTURE_CUBE_MAP_NEGATIVE_X

EGL_GL_TEXTURE_CUBE_MAP_POSITIVE_Y

EGL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Y

EGL_GL_TEXTURE_CUBE_MAP_POSITIVE_Z

EGL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Z

EGL_GL_TEXTURE_3D EGL_GL_RENDERBUFFER

Notes Used for GL 2D texture images Used for the +X face of GL cubemap texture images Used for the -X face of GL cubemap texture images Used for the +Y face of GL cubemap texture images Used for the -Y face of GL cubemap texture images Used for the +Z face of GL cubemap texture images Used for the -Z face of GL cubemap texture images Used for GL 3D texture images Used for GL renderbuffer images

Table 3.10: Legal values for eglCreateImage target parameter.

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3.9. EGLIMAGE SPECIFICATION AND MANAGEMENT Attribute EGL_NONE EGL_GL_TEXTURE_LEVEL

EGL_GL_TEXTURE_ZOFFSET

EGL_IMAGE_PRESERVED

Description Marks the end of the attribute-value list Specifies the mipmap level used as the EGLImage source. Must be part of the complete texture object buffer Specifies the depth offset of the image to use as the EGLImage source. Must be part of the complete texture object buffer Whether to preserve pixel data

Valid targets All

Default Value N/A

EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_*, EGL_GL_TEXTURE_3D

EGL_GL_TEXTURE_3D

All

EGL_FALSE

Table 3.11: Legal attributes for eglCreateImage attrib list parameter.

than x or greater than y are unspecified. For cubemaps a single pair x and y must apply to all faces. For three-dimensional textures, the specified z-offset must be smaller than the depth of the specified mipmap level. If target is EGL_GL_RENDERBUFFER, buffer must be the name of a complete, nonzero, non-multisampled GL_RENDERBUFFER (or equivalent in extensions) target object, cast into the type EGLClientBuffer. Values specified in attrib list are ignored. If the value of attribute EGL_IMAGE_PRESERVED is EGL_FALSE (the default), then all pixel data values associated with buffer will be undefined after eglCreateImage returns. If the value of attribute EGL_IMAGE_PRESERVED is EGL_TRUE, then all pixel data values associated with buffer are preserved. Errors eglCreateImage returns EGL_NO_IMAGE on failure. The contents of buffer will be unaffected. If dpy is not the handle of a valid EGLDisplay object, the error EGL_BAD_DISPLAY is generated. If ctx is neither the handle of a valid EGLContext object on dpy nor

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3.9. EGLIMAGE SPECIFICATION AND MANAGEMENT

EGL_NO_CONTEXT, the error EGL_BAD_CONTEXT is generated.

If target is not one of the values in table 3.10, the error EGL_BAD_PARAMETER is generated. If target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_*, EGL_GL_RENDERBUFFER or EGL_GL_TEXTURE_3D, and dpy is not a valid EGLDisplay, the error EGL_BAD_DISPLAY is generated. If target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_*, EGL_GL_RENDERBUFFER or EGL_GL_TEXTURE_3D, and ctx is not a valid EGLContext, the error EGL_BAD_CONTEXT is generated. If target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_*, EGL_GL_RENDERBUFFER or EGL_GL_TEXTURE_3D, and ctx is not a valid GL context, or does not match the dpy, the error EGL_BAD_MATCH is generated. If target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_* or EGL_GL_TEXTURE_3D and buffer is not the name of a texture object of type target, the error EGL_BAD_PARAMETER is generated. If target is EGL_GL_RENDERBUFFER and buffer is not the name of a renderbuffer object, or if buffer is the name of a multisampled renderbuffer object, the error EGL_BAD_PARAMETER is generated. If EGL_GL_TEXTURE_LEVEL is nonzero, target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_* or EGL_GL_TEXTURE_3D, and buffer is not the name of a complete GL texture object, the error EGL_BAD_PARAMETER is generated. If EGL_GL_TEXTURE_LEVEL is 0, target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_* or EGL_GL_TEXTURE_3D, buffer is the name of an incomplete GL texture object, and any mipmap levels other than mipmap level 0 are specified, the error EGL_BAD_PARAMETER is generated. If EGL_GL_TEXTURE_LEVEL is 0, target is EGL_GL_TEXTURE_2D or EGL_GL_TEXTURE_3D, buffer is not the name of a complete GL texture object, and mipmap level 0 is not specified, the error EGL_BAD_PARAMETER is generated. If EGL_GL_TEXTURE_LEVEL is 0, target is EGL_GL_TEXTURE_CUBE_MAP_*, buffer is not the name of a complete GL texture object, and one or more faces do not have mipmap level 0 specified, the error EGL_BAD_PARAMETER is generated. If target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_*, EGL_GL_RENDERBUFFER or EGL_GL_TEXTURE_3D and buffer refers to the default GL texture object (0) for the corresponding GL target, the error EGL_BAD_PARAMETER is generated. If target is EGL_GL_TEXTURE_2D, EGL_GL_TEXTURE_CUBE_MAP_*, or EGL_GL_TEXTURE_3D, and the value specified in attrib list for EGL_GL_EGL 1.5 - August 27, 2014

3.9. EGLIMAGE SPECIFICATION AND MANAGEMENT

TEXTURE_LEVEL is not a valid mipmap level for the specified GL texture object buffer, the error EGL_BAD_MATCH is generated. If target is EGL_GL_TEXTURE_3D, and the value specified in attrib list for EGL_GL_TEXTURE_ZOFFSET exceeds the depth of the specified mipmap level-of-detail in buffer, the error EGL_BAD_PARAMETER is generated.

If an attribute specified in attrib list is not one of the attributes shown in table 3.11, the error EGL_BAD_PARAMETER is generated. If an attribute specified in attrib list is not a valid attribute for target, as shown in table 3.11, the error EGL_BAD_MATCH is generated. If the resource specified by dpy, ctx, target, buffer and attrib list has an off-screen buffer bound to it (e.g., by a previous call to eglBindTexImage), the error EGL_BAD_ACCESS is generated. If the resource specified by dpy, ctx, target, buffer and attrib list is bound to an off-screen buffer (e.g., by a previous call to eglCreatePbufferFromClientBuffer), the error EGL_BAD_ACCESS is generated. If the resource specified by dpy, ctx, target, buffer and attrib list is itself an EGLImage sibling, the error EGL_BAD_ACCESS is generated. If insufficient memory is available to complete the specified operation, the error EGL_BAD_ALLOC is generated. If the value specified in attrib list for EGL_IMAGE_PRESERVED is EGL_TRUE, and an EGLImage handle cannot be created from the specified resource such that the pixel data values in buffer are preserved, the error EGL_BAD_ACCESS is generated. Note that the success or failure of eglCreateImage should not affect the ability to use buffer in its original API context (or context share group) (although the pixel data values will be undefined if the command succeeds and the value of EGL_IMAGE_PRESERVED is not EGL_TRUE).

3.9.1

Lifetime and Usage of EGLImages

Once an EGLImage is created from an EGLImage source, the memory associated with the EGLImage source will remain allocated (and all EGLImage siblings in all client API contexts will be useable) as long as either of the following conditions is true: • Any EGLImage siblings exist in any client API context • The EGLImage object exists inside EGL The semantics for specifying, deleting and using EGLImage siblings are client API-specific, and are described in the appropriate API specifications. EGL 1.5 - August 27, 2014

3.9. EGLIMAGE SPECIFICATION AND MANAGEMENT

If an application specifies an EGLImage sibling as the destination for rendering and/or pixel download operations (e.g., as an OpenGL or OpenGL ES framebuffer object, glTexSubImage2D, etc.), the modified image results will be observed by all EGLImage siblings in all client API contexts. If multiple client API contexts access EGLImage sibling resources simultaneously, with one or more context modifying the image data, rendering results in all contexts accessing EGLImage siblings are undefined. Respecification and/or deletion of any EGLImage sibling (i.e., both EGLImage source and EGLImage target resources) inside a client API context (by issuing a subsequent call to commands such as glTexImage* or glDeleteTextures, with the EGLImage sibling resource as the target of the operation) affects only that client API context and other contexts within its share group. For an OpenGL or OpenGL ES context, respecification always results in orphaning of the EGLImage, and may also include allocation of additional memory for the respecified resource and/or copying of the EGLImage pixel data23 . Operations inside EGL or any client API context which may affect the lifetime of an EGLImage (or the memory allocated for the EGLImage), such as respecifying and/or deleting an EGLImage sibling inside a client API context, must be atomic. Applications may create client API resources from an EGLImage using client API extensions outside the scope of this document (such as GL_OES_EGL_image, which creates OpenGL ES texture and renderbuffer objects). If the EGLImage used to create the client resource was created with the EGL_IMAGE_PRESERVED attribute set to EGL_TRUE, then the pixel data values associated with the image will be preserved after creating the client resource; otherwise, the pixel data values will be undefined. If the EGLImage was created with the EGL_IMAGE_PRESERVED attribute set to EGL_TRUE, and EGL is unable to create the client resource without modifying the pixel values, then creation will fail and the pixel data values will be preserved. The command EGLBoolean eglDestroyImage(EGLDisplay dpy, EGLImage image); is used to destroy the specified EGLImage object image. Once destroyed, image may not be used to create any additional EGLImage target resources within any client API contexts, although existing EGLImage siblings may continue to be used. EGL_TRUE is returned on success. 23 Behavior of other types of client APIs generally follows the OpenGL and OpenGL ES behavior described here, although this is not mandated yet.

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3.10. POSTING THE COLOR BUFFER

Errors On failure, eglDestroyImage returns EGL_FALSE If dpy is not the handle of a valid EGLDisplay object, the error EGL_BAD_DISPLAY is generated. If image is not a valid EGLImage object created with respect to dpy, the error EGL_BAD_PARAMETER is generated.

3.10

Posting the Color Buffer

After completing rendering, the contents of the color buffer can be made visible in a native window, or copied to a native pixmap.

3.10.1

Posting to a Window

To post the color buffer to a window, call EGLBoolean eglSwapBuffers(EGLDisplay dpy, EGLSurface surface); If surface is a back-buffered window surface, then the color buffer is copied to the native window associated with that surface. If surface is a single-buffered window, pixmap, or pbuffer surface, eglSwapBuffers has no effect. The contents of ancillary buffers are always undefined after calling eglSwapBuffers. The contents of the color buffer are undefined if the value of the EGL_SWAP_BEHAVIOR attribute of surface is not EGL_BUFFER_PRESERVED. The value of EGL_SWAP_BEHAVIOR can be set for some surfaces using eglSurfaceAttrib, as described in section 3.5.6. EGL_SWAP_BEHAVIOR applies only to the color buffer. EGL 1.5 has no way to specify or query whether or not ancillary buffers are preserved, and applications should not rely on this behavior. 3.10.1.1

Native Window Resizing

If the native window corresponding to surface has been resized prior to the swap, surface must be resized to match. surface will normally be resized by the EGL implementation at the time the native window is resized. If the implementation cannot do this transparently to the client, then eglSwapBuffers must detect the change and resize surface prior to copying its pixels to the native window. If surface shrinks as a result of resizing, some rendered pixels are lost. If surface grows, the newly allocated buffer contents are undefined. The resizing EGL 1.5 - August 27, 2014

3.10. POSTING THE COLOR BUFFER

behavior described here only maintains consistency of EGL surfaces and native windows; clients are still responsible for detecting window size changes (using platform-specific means) and changing their viewport and scissor regions accordingly.

3.10.2

Copying to a Native Pixmap

To copy the color buffer to a native pixmap, call EGLBoolean eglCopyBuffers(EGLDisplay dpy, EGLSurface surface, EGLNativePixmapType target); The color buffer is copied to the specified target, which must be a valid native pixmap handle. The mapping of pixels in the color buffer to pixels in the pixmap is platformdependent, since the native platform pixel coordinate system may differ from that of client APIs. The color buffer of surface is left unchanged after calling eglCopyBuffers.

3.10.3

Posting Semantics

surface must be bound to the draw surface of the calling thread’s current context, for the current rendering API. This restriction may be lifted in future EGL revisions. eglSwapBuffers and eglCopyBuffers perform an implicit flush operation on the context (glFlush for an OpenGL or OpenGL ES context, vgFlush for an OpenVG context). Subsequent client API commands can be issued immediately, but will not be executed until posting is completed. The destination of a posting operation (a visible window, for eglSwapBuffers, or a native pixmap, for eglCopyBuffers) should have the same number of components and component sizes as the color buffer it’s being copied from. In the specific case of a luminance color buffer being posted to an RGB destination, the luminance component value will normally be replicated in each of the red, green, and blue components of the destination. Some implementations may use alternate color-space conversion algorithms to map luminance to red, green, and blue values, so long as the perceptual result is unchanged. Such alternate conversions should be documented by the implementation. In other cases where this compatibility constraint is not met by the surface and posting destination, implementations may choose to relax the constraint by converting data to the destination format. If they do so, they should define an EGL EGL 1.5 - August 27, 2014

3.10. POSTING THE COLOR BUFFER

extension specifying which destination formats are supported, and specifying the conversion arithmetic used. The function EGLBoolean eglSwapInterval(EGLDisplay dpy, EGLint interval); specifies the minimum number of video frame periods per buffer swap for the draw surface of the current context, for the current rendering API. The interval takes effect when eglSwapBuffers is first called subsequent to the eglSwapInterval call. The swap interval has no effect on eglCopyBuffers. The parameter interval specifies the minimum number of video frames that are displayed before a buffer swap will occur. The interval specified by the function applies to the draw surface bound to the context that is current on the calling thread. If interval is set to a value of 0, buffer swaps are not synchronized to a video frame, and the swap happens as soon as all rendering commands outstanding for the current context are complete. interval is silently clamped to minimum and maximum implementation dependent values before being stored; these values are defined by EGLConfig attributes EGL_MIN_SWAP_INTERVAL and EGL_MAX_SWAP_INTERVAL respectively. The default swap interval is 1.

3.10.4

Posting Errors

Errors eglSwapBuffers and eglCopyBuffers return EGL_FALSE on failure. If surface is not a valid EGL surface, an EGL_BAD_SURFACE error is generated. If surface is not bound to the draw surface of the calling thread’s current context, an EGL_BAD_SURFACE error is generated. If target is not a valid native pixmap handle, an EGL_BAD_NATIVE_PIXMAP error should be generated. If the format of target is not compatible with the color buffer, or if the size of target is not the same as the size of the color buffer, and there is no defined conversion between the source and target formats, an EGL_BAD_MATCH error is generated. If called after a power management event has occurred, a EGL_CONTEXT_LOST error is generated. If eglSwapBuffers is called and the native window associated with surface is no longer valid, an EGL_BAD_NATIVE_WINDOW error is generated. EGL 1.5 - August 27, 2014

3.11. OBTAINING FUNCTION POINTERS

If eglCopyBuffers is called and the implementation does not support native pixmaps, an EGL_BAD_NATIVE_PIXMAP error is generated.

Errors eglSwapInterval returns EGL_FALSE on failure. If there is no current context on the calling thread, a EGL_BAD_CONTEXT error is generated. If there is no surface bound to the current context, a EGL_BAD_SURFACE error is generated.

3.11

Obtaining Function Pointers

The client API and EGL functions which are available to a client may vary at runtime, depending on factors such as the rendering path being used (hardware or software), resources available to the implementation, or updated device drivers. Therefore, the address of client API and EGL functions may be queried at runtime. The function void (*eglGetProcAddress(const char *procname))(void); returns the address of the function named by procName. procName must be a NULL-terminated string. The pointer returned should be cast to a function pointer matching the function’s definition in the corresponding API or extension specification. A return value of NULL indicates that the specified function does not exist for the implementation. A non-NULL return value for eglGetProcAddress does not guarantee that a function is actually supported at runtime. The client must also make a corresponding query, such as glGetString(GL_EXTENSIONS) for OpenGL and OpenGL ES extensions; vgGetString(VG_EXTENSIONS) for OpenVG extensions; or eglQueryString(dpy, EGL_EXTENSIONS) for EGL extensions; or query the EGL or client API version for non-extension functions, to determine if a function is supported by EGL or a specific client API context24 . 24

If a function is not supported by EGL or a specific client API context, the preferred behavior of calling through the function pointer is to generate an error, such as GL_INVALID_OPERATION for OpenGL and OpenGL ES contexts. However, undefined behavior up to and including program termination is possible.

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3.12. RELEASING THREAD STATE

Client API function pointers returned by eglGetProcAddress are independent of the display and the currently bound client API context, and may be used by any client API context which supports the function. eglGetProcAddress may be queried for all EGL and client API functions supported by the implementation (whether those functions are extensions or not, and whether they are supported by the current client API context or not). For functions that are queryable with eglGetProcAddress, implementations may choose to also export those functions statically from the object libraries implementing those functions. However, portable clients cannot rely on this behavior.

3.12

Releasing Thread State

EGL maintains a small amount of per-thread state, including the error status returned by eglGetError, the currently bound rendering API defined by eglBindAPI, and the current contexts for each supported client API. The overhead of maintaining this state may be objectionable in applications which create and destroy many threads, but only call EGL or client APIs in a few of those threads at any given time. To return EGL to its state at thread initialization, call EGLBoolean eglReleaseThread(void); EGL_TRUE is returned on success, and the following actions are taken:

• For each client API supported by EGL, if there is a currently bound context, that context is released. This is equivalent to calling eglMakeCurrent with ctx set to EGL_NO_CONTEXT and both draw and read set to EGL_NO_SURFACE (see section 3.7.3). • The current rendering API is reset to its value at thread initialization (see section 3.7). • Any additional implementation-dependent per-thread state maintained by EGL is marked for deletion as soon as possible. eglReleaseThread may be called in any thread at any time, and may be called more than once in a single thread. The initialization status of EGL (see section 3.2) is not affected by releasing the thread; only per-thread state is affected. Resources explicitly allocated by calls to EGL, such as contexts, surfaces, and configuration lists, are not affected by eglReleaseThread. Such resources belong not to the thread, but to the EGL implementation as a whole. EGL 1.5 - August 27, 2014

3.12. RELEASING THREAD STATE

Applications may call other EGL routines from a thread following eglReleaseThread, but any such call may reallocate the EGL state previously released. In particular, calling eglGetError immediately following a successful call to eglReleaseThread should not be done. Such a call will return EGL_SUCCESS but will also result in reallocating per-thread state. Errors eglReleaseThread returns EGL_FALSE on failure. There are no defined conditions under which failure will occur. Even if EGL is not initialized on any EGLDisplay, eglReleaseThread should succeed. However, platform-dependent failures may be signaled through the value returned from eglGetError. Unless the platform-dependent behavior is known, a failed call to eglReleaseThread should be assumed to leave the current rendering API, and the currently bound contexts for each supported client API, in an unknown state.

EGL 1.5 - August 27, 2014

Chapter 4

Extending EGL EGL implementors may extend EGL by adding new commands or additional enumerated values for existing EGL commands. New names for EGL functions and enumerated types must clearly indicate whether some particular feature is in the core EGL or is vendor specific. To make a vendor-specific name, append a company identifier (in upper case) and any additional vendor-specific tags (e.g. machine names). For instance, SGI might add new commands and manifest constants of the form eglNewCommandSGI and EGL_NEW_DEFINITION_SGI. If two or more vendors agree in good faith to implement the same extension, and to make the specification of that extension publicly available, the procedures and tokens that are defined by the extension can be suffixed by EXT. Extensions approved by supra-vendor organizations use similar identifiers, such as KHR for extensions approved by the Khronos Group). It is critically important for interoperability that enumerants and entry point names be unique across vendors. The Khronos API Registrar maintains a registry of enumerants, and all shipping enumerant values must be determined by requesting blocks of enumerants from the registry. See http://www.opengl.org/registry/ for more information on defining extensions.

Chapter 5

EGL Versions, Header Files, and Enumerants Each version of EGL supports specified client API versions, and all prior versions of those APIs up to that version. For OpenGL ES 1.x, such support includes both Common and Common-Lite profiles. EGL implementations may also support later versions of client APIs or additional client APIs, but such support will usually depend on vendor extensions. • EGL 1.0 supports OpenGL ES 1.0. • EGL 1.1 adds support for OpenGL ES 1.1. • EGL 1.2 adds support for OpenGL ES 2.0 and OpenVG 1.0. • EGL 1.4 adds support for all versions of OpenGL. • EGL 1.5 adds support for OpenGL ES 3.0, and for sharing events with OpenCL via sync objects. Whether a particular client API is actually available at runtime may depend on additional factors. In most cases, EGL and each client API are provided in separate libraries, and applications must link to the EGL library and to each of the client APIs used by the application. However, details of this procedure vary, and developers must refer to platform-specific documentation.

5.1

Header Files

The EGL specification defines an ISO C language binding. This binding may also be used from C++ code. In these environments, the EGL header file 86

5.2. COMPILE-TIME VERSION DETECTION

<EGL/egl.h> provides prototypes for all the EGL entry points, and C preprocessor symbols for all the EGL tokens. C and C++ source code should #include <EGL/egl.h> before using any EGL entry points or symbols1 Languages other than C and C++ will define the EGL interfaces using other methods, not described in this specification. The Khronos Implementers Guidelines describe recommended practice, outline platform-specific issues, and provide other recommendations to people writing EGL implementations. For more details refer to the developer area at: http://www.khronos.org/

5.2

Compile-Time Version Detection

To allow code to be written portably against future EGL versions, the compile-time environment must make it possible to determine which EGL version interfaces are available. The details of such detection are language-specific and should be specified in the language binding documents for each language. For C and C++ code, the <EGL/egl.h> header defines C preprocessor symbols corresponding to all versions of EGL supported by the implementation: #define EGL_VERSION_1_0 1 #define EGL_VERSION_1_1 1 #define EGL_VERSION_1_2 1 #define EGL_VERSION_1_3 1 #define EGL_VERSION_1_4 1 #define EGL_VERSION_1_5 1 Future versions of EGL will define additional preprocessor symbols corresponding to the major and minor numbers of those versions.

5.3

Enumerant Values and Header Portability

Enumerant values for EGL tokens are required to be common across all implementations. A reference version of the egl.h header file, including defined values for all EGL enumerants, accompanies this specification and can be downloaded from http://www.khronos.org/ 1

For backwards compatibility, implementations supporting OpenGL ES 1.x must also support the EGL header on the path <GLES/egl.h>.

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5.3. ENUMERANT VALUES AND HEADER PORTABILITY

All platform-specific types, values, and macros used in egl.h are partitioned into a platform header, eglplatform.h, which is automatically included by egl.h. A copy of eglplatform.h providing definitions suitable for many platforms is included along with egl.h. Implementers should need to modify only eglplatform.h, never egl.h2 .

Please submit any additions to eglplatform.h made to support new platforms for inclusion in the reference copy.

EGL 1.5 - August 27, 2014

Chapter 6

Glossary Address Space the set of objects or memory locations accessible through a single name space. In other words, it is a data region that one or more threads may share through pointers. Client an application, which communicates with the underlying EGL implementation and underlying platform by some path. The application program is referred to as a client of the platform server. To the server, the client is the communication path itself. A program with multiple connections is viewed as multiple clients to the server. The resource lifetimes are controlled by the connection lifetimes, not the application program lifetimes. Client API one of the rendering APIs supported by EGL. At present client APIs include OpenGL, OpenGL ES and OpenVG, but other clients are expected to be added in future versions of EGL. Context creation / management, rendering semantics, and interaction between client APIs are all well-defined by EGL. There is (considerably more limited) support for rendering to EGL surfaces by non-client (native) rendering APIs, and the semantics of such support are more implementation-dependent. Compatible an OpenGL or OpenGL ES rendering context is compatible with (may be used to render into) a surface if they meet the constraints specified in section 2.2. Connection a bidirectional byte stream that carries the X (and EGL) protocol between the client and the server. A client typically has only one connection to a server. (Rendering) Context an OpenGL or OpenGL ES rendering context. This is a virtual machine. All OpenGL or OpenGL ES rendering is done with respect 89

90 to a context. The state maintained by one rendering context is not affected by another except in case of state that may be explicitly shared at context creation time, such as textures. Current Context an implicit context used by OpenGL, OpenGL ES and OpenVG, rather than passing a context parameter to each API entry point. The current OpenGL, OpenGL ES and OpenVG contexts are set as defined in section 3.7.3. EGLContext a handle to a rendering context. OpenGL and OpenGL ES rendering contexts consist of client side state and server side state. Other client APIs do not distinguish between the two types of state. EGLImage An opaque handle to a shared resource created by EGL client APIs, presumably a 2D array of image data EGLImage Source An object or sub-object originally created in a client API (such as a mipmap level of a texture object in OpenGL or OpenGL ES, or a VGImage in OpenVG) which is used as the buffer parameter in a call to eglCreateImage. EGLImage Target An object created in a client API (such as a texture object in OpenGL ES or a VGImage in OpenVG) from a previously-created EGLImage EGLImage Sibling The set of all EGLImage targets (in all client API contexts) which are created from the same EGLImage object, and the EGLImage source resouce which was used to create that EGLImage. Orphaning The process of respecifying and/or deleting an EGLImage sibling resource (inside a client API context) which does not result in deallocation of the memory associated with the EGLImage or affect rendering results using other EGLImage siblings. Referencing The process of creating an EGLImage target resource (inside a client API context) from an EGLImage. Respecification When the size, format, or other attributes of an EGLImage sibling are changed via client API calls such as gl*TexImage*. Respecification usually will result in orphaning the sibling. Note that changing the pixel values of the sibling (e.g. by rendering to it or by calling gl*TexSubImage*) does not constitute respecification.

EGL 1.5 - August 27, 2014

91 (Drawing) Surface an onscreen or offscreen buffer where pixel values resulting from rendering through OpenGL ES or other APIs are written. Thread one of a group of execution units all sharing the same address space. Typically, each thread will have its own program counter and stack pointer, but the text and data spaces are visible to each of the threads. A thread that is the only member of its group is equivalent to a process.

EGL 1.5 - August 27, 2014

Appendix A

Version 1.0 EGL version 1.0, approved on July 23, 2003, is the original version of EGL. EGL was loosely based on GLX 1.3, generalized to be implementable on many different operating systems and window systems and simplified to reflect the needs of embedded devices running OpenGL ES.

A.1

Acknowledgements

EGL 1.0 is the result of the contributions of many people, representing a cross section of the desktop, hand-held, and embedded computer industry. Following is a partial list of contributors, including the company that they represented at the time of their contribution: Aaftab Munshi, ATI Andy Methley, Panasonic Carl Korobkin, 3d4W Chris Hall, Seaweed Systems Claude Knaus, Silicon Graphics David Blythe, 3d4W Ed Plowman, ARM Graham Connor, Imagination Technologies Harri Holopainen, Hybrid Graphics Jacob Ström, Ericsson Jani Vaarala, Nokia

Jon Leech, Silicon Graphics Justin Couch, Yumetech Kari Pulli, Nokia Lane Roberts, Symbian Mark Callow, HI Mark Tarlton, Motorola Mike Olivarez, Motorola Neil Trevett, 3Dlabs Phil Huxley, Tao Group Tom Olson, Texas Instruments Ville Miettinen, Hybrid Graphics

Appendix B

Version 1.1 EGL version 1.1, approved on August 5, 2004, is the second release of EGL. It adds power management and swap control functionality based on vendor extensions from Imagination Technologies, and optional render-to-texture functionality based on the WGL_ARB_render_texture extension defined by the OpenGL ARB for desktop OpenGL.

B.1

Revision 1.1.2

EGL version 1.1.2 (revision 2 of EGL 1.1), approved on November 10, 2004, clarified that vertex buffer objects are shared among contexts in the same fashion as texture objects.

B.2

Acknowledgements

EGL 1.1 is the result of the contributions of many people, representing a cross section of the desktop, hand-held, and embedded computer industry. Following is a partial list of contributors, including the company that they represented at the time of their contribution: Aaftab Munshi, ATI Andy Methley, Panasonic Axel Mamode, Sony Barthold Lichtenbelt, 3Dlabs Benji Bowman, Imagination Technologies Borgar Ljosland, Falanx Brian Murray, Motorola Bryce Johnstone, Texas Instruments

Carlos Sarria, Imagination Technologies Chris Tremblay, Motorola Claude Knaus, Esmertec Clay Montgomery, Nokia Dan Petersen, Sun Dan Rice, Sun David Blythe, HI David Yoder, Motorola

B.2. ACKNOWLEDGEMENTS

Doug Twilleager, Sun Ed Plowman, ARM Graham Connor, Imagination Technologies Greg Stoner, Motorola Hannu Napari, Hybrid Harri Holopainen, Hybrid Jacob Ström, Ericsson Jani Vaarala, Nokia Jerry Evans, Sun John Metcalfe, Imagination Technologies Jon Leech, Silicon Graphics Kari Pulli, Nokia Lane Roberts, Symbian Madhukar Budagavi, Texas Instruments Mathias Agopian, PalmSource Mark Callow, HI

Mark Tarlton, Motorola Mike Olivarez, Motorola Neil Trevett, 3Dlabs Nick Triantos, Nvidia Petri Kero, Hybrid Petri Nordlund, Bitboys Phil Huxley, Tao Group Remi Arnaud, Sony Robert Simpson, Bitboys Tero Sarkkinen, Futuremark Timo Suoranta, Futuremark Thomas Tannert, Silicon Graphics Tomi Aarnio, Nokia Tom McReynolds, Nvidia Tom Olson, Texas Instruments Ville Miettinen, Hybrid Graphics

EGL 1.5 - August 27, 2014

Appendix C

Version 1.2 EGL version 1.2, approved on July 8, 2005, is the third release of EGL. It adds support for the OpenVG 2D client API, in addition to support for OpenGL ES, and generalizes EGL concepts to enable supporting other client APIs in the future.

C.1

Acknowledgements

EGL 1.2 is the result of the contributions of many people, representing a cross section of the desktop, hand-held, and embedded computer industry. Following is a partial list of contributors, including the company that they represented at the time of their contribution: Aaftab Munshi, ATI Anu Ramanathan, TI Daniel Rice, Sun Microsystems Espen Aamodt, Falanx Jani Vaarala, Nokia Jon Leech, SGI Jussi Räsänen, Hybrid Graphics Koichi Mori, Nokia Mark Callow, HI Corporation Members of the Khronos OpenGL ES Work-

ing Group Members of the Khronos OpenVG Working Group Michael.Nonweiler, ARM Neil Trevett, 3Dlabs / NVIDIA Petri Kero, Hybrid Graphics Robert Simpson, Bitboys Simon Fenney, PowerVR Tom Olson, TI

Appendix D

Version 1.3 EGL version 1.3 was voted out of the OpenKODE Working Group on December 4, 2006, and formally approval by the Khronos Board of Promoters on February 8, 2007. EGL 1.3 is the fourth release of EGL. It adds support for separate OpenGL ES 1.x and 2.x contexts with the EGL_CONTEXT_CLIENT_VERSION attribute to eglCreateContext and the EGL_OPENGL_ES2_BIT in the EGL_RENDERABLE_TYPE attribute, and adds the EGL_MATCH_NATIVE_PIXMAP pseudo-attribute to eglChooseConfig, to allow selecting configs matching specific native pixmaps. The EGL_CONFORMANT attribute was added to indicate if client API contexts will pass the required conformance tests, and the EGL_SURFACE_TYPE attribute was extended with the EGL_VG_COLORSPACE_LINEAR_BIT and EGL_VG_ALPHA_FORMAT_PRE_BIT bitfields to define whether or not linear colorspace and premultiplied alpha format are supported by the OpenVG implementation. For naming consistency, some tokens from EGL 1.2 have been renamed as shown in table D.1. The old names are also retained for backwards compatibility. The specification adds a number of clarifications (but not behavior changes) regarding config sorting, surface resource ownership, multiple client API context versions, and SDK issues. Finally, the eglplatform.h header is defined to accompany the reference egl.h header provided by Khronos.

D.1

Acknowledgements

EGL 1.3 is the result of the contributions of many people, representing a cross section of the desktop, hand-held, and embedded computer industry. Following is a list of contributors, including the company that they represented at the time of their contribution: 96

D.1. ACKNOWLEDGEMENTS

EGL 1.2 Token Name

EGL 1.3 Token Name

EGL_COLORSPACE EGL_COLORSPACE_LINEAR EGL_COLORSPACE_sRGB EGL_ALPHA_FORMAT EGL_ALPHA_FORMAT_PRE EGL_ALPHA_FORMAT_NONPRE

EGL_VG_COLORSPACE EGL_VG_COLORSPACE_LINEAR EGL_VG_COLORSPACE_sRGB EGL_VG_ALPHA_FORMAT EGL_VG_ALPHA_FORMAT_PRE EGL_VG_ALPHA_FORMAT_NONPRE

NativeDisplayType NativePixmapType NativeWindowType

EGLNativeDisplayType EGLNativePixmapType EGLNativeWindowType

Table D.1: Renamed tokens

Aaftab Munshi, ATI Daniel Rice, Sun Microsystems Espen Aamodt, Falanx Gary King, NVIDIA Jani Vaarala, Nokia Jasin Bushnaief, Hybrid Graphics Jay Abbott, TAO Jon Kennedy, 3Dlabs Jon Leech Jussi Räsänen, Hybrid Graphics Kalle Raita, Hybrid Graphics Kari Pulli, Nokia Koichi Mori, Nokia Leonardo Estevez, TI Mark Callow, HI Corporation Members of the Khronos OpenGL ES Work-

ing Group Members of the Khronos OpenKODE Working Group Members of the Khronos OpenVG Working Group Neil Trevett, NVIDIA Petri Kero, Hybrid Graphics Remi Arnaud, Sony Computer Entertainment Robert J. Simpson, Bitboys Robert Palmer, Symbian Sampo Lappalainen, Hybrid Graphics Simon Fenney, Imagination Technologies Sven Gothel, ATI Teemu Rantalaiho, Hybrid Graphics Tom Olson, TI

EGL 1.5 - August 27, 2014

Appendix E

Version 1.4 EGL version 1.4 was voted out of the Khronos Technical Working Group on March 25, 2008, and formally approved by the Khronos Board of Promoters on May 29, 2008. EGL 1.4 is the fifth release of EGL. It introduces the following new features: • Allow multisampled configurations for OpenVG, by relaxing OpenGL ESspecific language and documenting that multisample buffer resolution may be performed when switching which client API is rendering to a surface. • Allow control of multisample resolution behavior (use of a box filter) using the EGL_MULTISAMPLE_RESOLVE EGLSurface attribute. • Allow control of swap behavior (preserving back buffer contents) using the EGL_SWAP_BEHAVIOR bit in the EGL_SURFACE_TYPE EGLSurface attribute. • Enable support for OpenGL (in addition to, or instead of OpenGL ES) as a client API. • Relax definition of EGLNativeDisplayType to allow a variety of mappings to X and Microsoft Windows data structures. • Document the meaning of the EGL_LEVEL EGLConfig attribute. • Document that eglMakeCurrent can raise an EGL_BAD_ACCESS error when binding more contexts in the current thread group than are supported by the implementation. • Add a specific example of how eglCreatePbufferFromClientBuffer can fail due to implementation constraints. 98

E.1. UPDATES TO EGL 1.4

• Fix prototypes of functions with empty argument lists.

E.1

Updates to EGL 1.4

After the initial version of EGL 1.4 was released, minor changes and corrections were made in later revisions as described below. Changes in the revision approved on January 20, 2009: • Change object destruction behavior such that object handles become invalid immediately after an object is deleted, although the underlying object may remain valid if it’s current to a context. This affects eglTerminate (section 3.2), eglDestroySurface (section 3.5.5), eglDestroyContext (section 3.7.2), and eglGetCurrentContext and eglGetCurrentSurface (section 3.7.4). • Clarify initialization and termination behavior of EGLDisplays, and behavior of EGL functions when passed an uninitialized display, in sections 3.2 and 3.7.3. Changes in the revision approved on April 15, 2009: • Specified in section 2.1.2 that all objects exist in the namespace of an EGLDisplay (bug 4303). • Clarified meaning of EGL_PIXEL_ASPECT_RATIO and the purpose of EGL_DISPLAY_SCALING in section 3.5.6 (bug 3594). Changes in the revision approved on June 23, 2009: • Expanded description of “generic” errors applying to multiple commands in section 3.1 (bug 4993). • Noted in sections 3.7.4 and 3.7.3 that EGL_NO_DISPLAY is not a valid EGLDisplay, and passing it as a display parameter should generate errors (bug 4993). • Added clarification of meaning of config masks in section 3.4.1 (bug 5276). Changes in the revision approved on September 25, 2009:

EGL 1.5 - August 27, 2014

E.1. UPDATES TO EGL 1.4

100

• Updated language in section 3.5.1 to make clear that the window system (as well as EGL and client APIs other than OpenVG) is not necessarily affected by the value of the EGL_VG_ALPHA_FORMAT attribute, and that preferred window system behavior is to ignore EGL_VG_ALPHA_FORMAT (bug 5526). • Clarified error conditions for eglCreatePbufferFromClientBuffer in section 3.5.3 (bug 5473). Changes in the revision approved on March 3, 2010: • Change descriptions of EGL_SWAP_BEHAVIOR_PRESERVED_BIT in table 3.2 and EGL_SWAP_BEHAVIOR in section 3.4 to specify that they apply only to the color buffer. Relax language in section 3.10.1 to allow ancillary buffer contents to be undefined after swap, regardless of the value of EGL_SWAP_BEHAVIOR; clarify how EGL_SWAP_BEHAVIOR controls color buffer preservation; and add a footnote describing this subtle behavior change relative to older versions of EGL 1.4 (bug 5970). Changes in the revision approved on April 7, 2010: • Update table 3.1 and the description of EGL_BUFFER_SIZE in section 3.4 to clarify that this attribute is simply the sum of the RGBA or LA component sizes, and does not include any padding or alignment bits that may be present in the underlying pixel format (bug 6143). Changes in the revision approved on May 21, 2010: • Note that EGL_MATCH_NATIVE_PIXMAP is not a valid attribute to eglGetConfigAttrib in section 3.4.3 (bug 6285). Changes in the revision approved on July 21, 2010: • Clarify lifetime of shared objects when contexts on the share list are destroyed in section 3.7.2 (Bug 6582). Changes in the revision approved on October 6, 2010: • Fix typo in section 2.4 (public Bug 340). • Refine eglTerminate language in section 3.2 to specify that handles to all types of EGL resources owned by the terminated display are invalidated, although the display handle itself remains valid (Bug 6776). EGL 1.5 - August 27, 2014

E.1. UPDATES TO EGL 1.4

101

• Fix error condition for eglCreateWindowSurface in section 3.5.1 to be generated if there is already an EGLSurface associated with the native window, rather than an EGLConfig (Bug 6667). • Expand footnote describing counterintuitive behavior of EGLConfig sort rule 3 in section 3.4.1 (public Bug 327). • Add Tero Pihlajakoski to the Acknowledgements. Changes in the revision approved on April 20, 2011: • Note that EGL_DONT_CARE is not a valid attribute value for EGL_MATCH_NATIVE_PIXMAP in section 3.4.1 (Bug 7456). • Correct sort order of EGL_COLOR_BUFFER_TYPE in table 3.4 (Bug 7431). Changes in the revision approved on February 13, 2013: • Clarify support for OpenGL as well as OpenGL ES in sections 1, 2.2, 2.2, 2.2.2, 2.3, 2.4, 2.6, and 5 (Bug 9864). • Added new section 2.2.2.1, clarifying that the y coordinate used when rendering to native window or pixmap surfaces is inverted relative to the client API coordinate system, so that images appear as expected. N.b. this is not a behavior change (Bug 9701). • Note in section 3.1 that since eglGetError always returns error information about the most recently called EGL function, calling eglGetError twice in a row will return EGL_SUCCESS on the second call. • Add language to the description of eglBindAPI in section 3.7 making EGL_OPENGL_API and EGL_OPENGL_ES_API equivalent for all purposes other than eglCreateContext, and added eglCopyBuffers and eglSwapBuffers to the list of commands affected by the current rendering API (Bug 9118). • Minor language fixes to description of eglGetProcAddress in section 3.11 (Bug 9865). • Clarify support for OpenGL as well as OpenGL ES in chapter 6 (Bug 9864). Changes in the revision approved on December 4, 2013: • Modified the definition of EGLint in section 2.1.1 so that it may not be large enough to hold a native pointer, and described why the regression is being adopted (Bug 11027). EGL 1.5 - August 27, 2014

E.2. ACKNOWLEDGEMENTS

102

• Updated section 2.2.2.1 to not mandate that all window systems invert the coordinate system relative to client APIs (Bug 9701). • Change selection type of EGL_CONFIG_ID from Exact to Special in table 3.4 (Bug 10567). • Added new section 3.7.3.2 specifying that EGL does not provide ordering guarantees across eglMakeCurrent (Bug 10664). • Change description of eglQueryContext query in section 3.7.4 so EGL_CONTEXT_CLIENT_VERSION returns the version of the context actually created, not the version requested (Bug 10906). • Clarify that querying EGL_RENDER_BUFFER returns values depending on the draw surface in section 3.7.4; that eglWaitClient and eglWaitNative guarantee synchronization to both read and draw surfaces in section 3.8; and that eglSwapInterval affects, and eglSwapBuffers and eglCopyBuffers are restricted to the currently bound draw surface in sections 3.10.3 and 3.10.4 (Bug 10200). • Add a footnote to the description of eglGetProcAddress in section 3.11 clarifying that calling through an extension function pointer to an extension not implemented by a client API results in undefined behavior (Bug 10147).

E.2

Acknowledgements

EGL 1.4 is the result of the contributions of many people, representing a cross section of the desktop, hand-held, and embedded computer industry. Following is a list of contributors, including the company that they represented at the time of their contribution: Acorn Pooley, NVIDIA Andrzej Mamona, AMD Barthold Lichtenbelt, NVIDIA Benj Lipchak, AMD Benji Bowman, Imagination Technologies Bill Licea-Kane, AMD Dongkyun Jeong, Samsung Ed Plowman, ARM Gabriele Svelto, ST Microelectronics Gary King, NVIDIA Georg Kolling, Imagination Technologies Graham Connor, Imagination Technologies

Ian Romanick, Intel Jim Van Welzen, NVIDIA Jon Leech Kari Pulli, Nokia Leonardo Estevez, TI Mark Callow, HI Corporation Marko Lukat, Antix Labs Matti Paavola, Nokia Maurice Ribble, AMD Members of the Khronos OpenGL ES, OpenKODE, OpenMAX, OpenVG, and OpenWF Working Groups

EGL 1.5 - August 27, 2014

E.2. ACKNOWLEDGEMENTS

Michael Giovinco, Seaweed Systems Neil Trevett, NVIDIA Pasi Keranen, Nokia Pierre Boudier, AMD Richard Sahlin, Ericsson Robert Palmer, Symbian Robert Simpson, AMD Roger Nixon, Broadcom

103

Sami Kyostila, Nokia Steven Fischer, Motorola Tero Pihlajakoski, Symbio Tim Renouf, Antix Labs Tom Olson, TI Yeshwant Muthusamy, Nokia Zhifang Long, Marvell

EGL 1.5 - August 27, 2014

Appendix F

Version 1.5 EGL version 1.5 was voted out of the Khronos Technical Working Group on January 31, 2014, and formally approved by the Khronos Board of Promoters on March 14, 2014. EGL 1.5 is the sixth release of EGL. It introduces the following new features (the EGL extension(s) each feature is based on are also shown parenthetically): • Platform support: – Distinguishing client and display extensions, and defining a method to query, without initializing a display, the set of supported client extensions (EGL_EXT_client_extensions). – Providing a mechanism for support of multiple platforms (such as window systems or offscreen rendering frameworks) in a single EGL implementation at runtime (EGL_EXT_platform_base). • Client API interoperability: – Sync objects representing events whose completion can be tested or waited on. Such events include fences placed in client API command streams (EGL_KHR_fence_sync) and events triggered by OpenCL event objects (EGL_KHR_cl_event2), and the ability to wait for sync objects in the server for a client API context, allowing application code to continue to execute in parallel (EGL_KHR_wait_sync). • Image sharing: – Definition of image objects suitable for sharing 2D arrays of image data between client APIs (EGL_KHR_image_base) 104

F.1. CHANGE LOG FOR RELEASED SPECIFICATIONS

105

– Methods to create image objects from OpenGL and OpenGL ES API resources including two- and three-dimensional textures, cube maps and render buffers (EGL_KHR_gl_texture_2D_image, EGL_KHR_gl_texture_3D_image, EGL_KHR_gl_texture_cubemap_image, and EGL_KHR_gl_renderbuffer_image). • General API cleanup: – A new context creation command with attributes specifying the requested OpenGL and OpenGL ES version, context properties, profile, and the ability to be made current without providing a default framebuffer (EGL_KHR_create_context), as well as robust buffer access behavior and graphics reset notification behavior (EGL_EXT_create_context_robustness). – Defining eglGetProcAddress to support querying of all EGL and client API functions, not just extensions (EGL_KHR_get_all_proc_addresses and EGL_KHR_client_get_all_proc_addresses). – Enabling creation of EGLSurfaces which will be rendered to in sRGB by OpenGL and OpenGL ES contexts supporting that capability (EGL_KHR_gl_colorspace). – Extending eglMakeCurrent to make a context current without either a read of draw surface (EGL_KHR_surfaceless_context).

F.1

Change Log for Released Specifications

Changes in the revision approved on August 27, 2014: • Remove language in section 3.9 stating that inapplicable attributes to eglCreateImage are ignored, since this is inconsistent with the explicit error defined for this case (Bug 12585). Changes in the revision approved on May 21, 2014: • Allow querying the EGL client version string by passing EGL_NO_DISPLAY to eglQueryString in section 3.3 (Bug 12204), and define the meaning of the client version (Bug 12204). • Change error code for invalid type arguments to eglCreateSync to EGL_BAD_PARAMETER in section 3.8.1 (Bug 11963). EGL 1.5 - August 27, 2014

F.1. CHANGE LOG FOR RELEASED SPECIFICATIONS

106

• Document in section 3.9.1 that respecification of an EGLImage sibling in an OpenGL or OpenGL ES context results in orphaning of the EGLImage (Bug 11851). Changes in the initial release of March 12, 2014, relative to the EGL 1.4 Specification: • Add new features as described in section F. • Minor typos and fixes - add OpenCL to section 1, add missing EGL types to section 2.1.1 and display-destruction discussion in section 3.2, retitle section 3.3 more generically, clarify applicability of EGL_LEVEL in section 3.4, fix parameter name for native window in section 3.5.1, clarify allowed types of OpenCL events in section 3.8.1.2, typos in sections 3.9 and 3.11 (Bug 11577). • Add footnote to description of EGLAttrib in section 2.1.1 explaining why not all EGL features using attribute lists have been updated to support EGLAttrib interface variants (Bug 11850). • Added eglSwapInterval to the list of commands affected by the current rendering API set with eglBindAPI in section 3.7 (Bug 11384). • Modify description of context reset notification strategy in section 3.7.1.6 to describe as relevant, but not require EXT extensions (Bug 9313). • Change eglCreateContext error in section 3.7.1.6 when config does not support the requested client API from EGL_BAD_CONFIG to EGL_BAD_MATCH, and clarify that the final EGL_BAD_MATCH error is intended as the error to be generated if context creation failed for reasons not enumerated previously in the Errors section (Bug 11562). • Remove redundant error for eglCreateContext in section 3.7.1.6, and remove error when specifying an OpenGL profile mask for a context version that doesn’t support profiles (Bug 11562). • Clarify that the GL viewport/scissor context state initialization described in section 3.7.3 only applies when a context is made current for the first time and it is without a default framebuffer. • Clarify completeness requirements on GL textures passed to eglCreateImage in section 3.9 (Bug 11081).

EGL 1.5 - August 27, 2014

F.2. ACKNOWLEDGEMENTS

F.2

107

Acknowledgements

EGL 1.5 is the result of the contributions of many people, representing a cross section of the desktop, hand-held, and embedded computer industry. Following is a list of contributors, including the company that they represented at the time of their contribution: Some major contributions made by individuals are listed together with their name. NVIDIA (EGL_KHR_surfaceless_context)

Acorn Pooley,

Adrian Bucur, Samsung Alex Walters, Imagination Technologies Alon Or-bach, Samsung (Khronos EGL Working Group Chair) Anders Pedersen, ARM Barthold Lichtenbelt, NVIDIA Benji Bowman, Imagination Technologies Benoit Jacob, Mozilla Brian Ellis, Qualcomm Brian Murray, Freescale Brian Paul, VMware Bruce Merry, ARM Chad Versace, Intel (EGL_EXT_client_extensions, EGL_EXT_platform_base) Chris Knox, NVIDIA Chris Wynn, NVIDIA Christopher James Halse Rogers, Canonical Daniel Koch, NVIDIA David Garcia, Qualcomm Endre Sund, ARM Gary King, NVIDIA (EGL_KHR_image_base, EGL_KHR_gl_*_image) Georg Kolling, Imagination Technologies Graeme Leese, Broadcom Graham Sellers, AMD Greg Roth, NVIDIA (EGL_EXT_-

create_context_robustness) Greg Stoner, AMD Gregory Prisament, NVIDIA Hans-Martin Will Hwanyong Lee, Kyungpook National University Ian Romanick, Intel Insu Yu, Samsung Jakob Bornecrantz, VMware

Jones, NVIDIA (EGL_KHR_client_get_all_proc_addresses, EGL_KHR_get_all_proc_addresses)

James

Jamie Gennis, Google Jan-Harald Fredriksen, ARM Jeff Bolz, NVIDIA Jeff Juliano, NVIDIA Jeff Vigil, Qualcomm Jeffrey McGee, TI Jens Owen, LunarG Jeremy Hewitson, Nokia Jesse Barker, Linaro Jesse Hall, Google Jim Van Welzen, NVIDIA Joel Pilon, QNX Jon Leech (EGL 1.5 Specification Editor, EGL_KHR_cl_event2, EGL_KHR_create_context, EGL_KHR_fence_sync, EGL_KHR_gl_colorspace, EGL_KHR_wait_sync) Jonathan Grant, Renesas JungWoo Kim, Samsung Kalle Raita, drawElements Kari Pulli, NVIDIA Kenneth Russell, Google Kristian Kristensen, Intel Lars Remes, Ardites Magnus Wendt, ST Ericsson Marcus Lorentzon, ST Ericsson Mark Callow, Artspark Marko Lukat, Antix Labs Matteo Salardi, Imagination Technologies Matthew Porth, Samsung Matti Paavola, Nokia Maurice Ribble, Qualcomm Members of the Khronos OpenGL ARB and OpenGL ES Working Groups

EGL 1.5 - August 27, 2014

F.2. ACKNOWLEDGEMENTS

Mikael Beckius, Sony Ericsson Mikael Sevenier, Aptina Mike Weiblen, Transgaming Neil Trevett, NVIDIA (Khronos EGL Working Group Chair) Nicholas Haemel, NVIDIA Pasi Keranen, Nokia Pierre Boudier, AMD Piotr Tomaszewski, ST Ericsson Prabindh Sundareson, TI Rathinasamy Rajesh, Nokia Raymond Smith, ARM Remi Arnaud Rob Barris, NVIDIA Robert Bragg, Intel Robert Palmer, Nokia Roger Nixon, Broadcom Rufus Hamade, Imagination Technologies

108

Sami Kyöstilä, Nokia Shereef Shehata, TI Steven Fischer, Motorola Steven Holte, NVIDIA Szabolcs Tolnai, Imagination Technologies Tero Pihlajakoski, Symbio Tewari Anshuman Thierry Vuillaume, ST Ericsson Tim Renouf, Antix Timo Suoranta, Broadcom Tom Cooksey, ARM Tom Longo, AMD Tom Olson, ARM Vlad Mann, Nokia Vladimir Vukicevic, Mozilla Wes Bang, Nokia Yanjun Zhang, Vivante Yeshwant Muthusamy, Samsung

EGL 1.5 - August 27, 2014

Index CL COMPLETE, 67 cl khr egl image, 66 CL QUEUED, 67 CL RUNNING, 67 CL SUBMITTED, 67 Display, 15 EGL ALPHA FORMAT, 97 EGL ALPHA FORMAT NONPRE, 97 EGL ALPHA FORMAT PRE, 97 EGL ALPHA MASK SIZE, 20, 21, 29, 30 EGL ALPHA SIZE, 20, 21, 29, 30, 38, 47 EGL BACK BUFFER, 32, 33, 45, 46, 49, 63 EGL BAD ACCESS, 12, 39, 48, 58, 77, 98 EGL BAD ALLOC, 13, 34, 37, 41, 57, 59, 60, 77 EGL BAD ATTRIBUTE, 13, 27, 31, 37, 46, 55, 64, 68, 71 EGL BAD CONFIG, 13, 34, 37, 41, 56, 106 EGL BAD CONTEXT, 13, 16, 56, 57, 59, 64, 76, 82 EGL BAD CURRENT SURFACE, 13, 59, 64, 65 EGL BAD DISPLAY, 13, 14, 16, 17, 19, 59, 62, 68, 75, 76, 79 EGL BAD MATCH, 13, 34, 37–39, 41,

43, 48, 49, 55–59, 68, 70, 72, 76, 77, 81, 106 EGL BAD NATIVE PIXMAP, 13, 14, 41, 81, 82 EGL BAD NATIVE WINDOW, 14, 34, 59, 81 EGL BAD PARAMETER, 13, 15, 19, 26, 37, 38, 43, 48, 49, 51, 62, 65, 68, 70–72, 76, 77, 79, 105 EGL BAD SURFACE, 13, 16, 42, 46, 48, 49, 59, 81, 82 EGL BIND TO TEXTURE RGB, 20, 26, 29, 30, 46, 49 EGL BIND TO TEXTURE RGBA, 20, 26, 29, 30, 46, 49 EGL BLUE SIZE, 20, 21, 29, 30, 38, 47 EGL BUFFER DESTROYED, 43, 45 EGL BUFFER PRESERVED, 43, 45, 79 EGL BUFFER SIZE, 20, 21, 29, 30, 100 EGL CL EVENT HANDLE, 67, 68 EGL CLIENT APIS, 18 EGL COLOR BUFFER TYPE, 20, 21, 29, 30, 101 EGL COLORSPACE, 97 EGL COLORSPACE LINEAR, 97 EGL COLORSPACE sRGB, 97 EGL CONDITION SATISFIED, 69 EGL CONFIG CAVEAT, 20, 24, 28, 29

109

INDEX

110

EGL CONFIG ID, 19, 20, 28–30, 43, 44, 63, 102 EGL CONFORMANT, 20, 24, 25, 29, 30, 96 EGL CONTEXT CLIENT TYPE, 63 EGL CONTEXT CLIENT VERSION, 52, 63, 96, 102 EGL CONTEXT FORWARD COMPATIBLE, 54 EGL CONTEXT LOST, 10, 14, 59, 81 EGL CONTEXT MAJOR VERSION, 52, 53 EGL CONTEXT MINOR VERSION, 52, 53 EGL CONTEXT OPENGL COMPATIBILITY PROFILE BIT, 53, 57 EGL CONTEXT OPENGL CORE PROFILE BIT, 53, 54, 57 EGL CONTEXT OPENGL DEBUG, 54 EGL CONTEXT OPENGL FORWARD COMPATIBLE, 54 EGL CONTEXT OPENGL PROFILE MASK, 53, 54 EGL CONTEXT OPENGL RESET NOTIFICATION STRATEGY, 55 EGL CONTEXT OPENGL ROBUST ACCESS, 55 EGL CORE NATIVE ENGINE, 65 EGL DEFAULT DISPLAY, 16 EGL DEPTH SIZE, 20, 21, 29, 30 EGL DISPLAY SCALING, 45, 99 EGL DONT CARE, 27, 29, 30, 101 EGL DRAW, 62 EGL EXT client extensions, 104, 107 EGL EXT create context robustness, 105, 107

EGL EXT platform base, 104, 107 EGL EXTENSIONS, 2, 18, 19, 82 EGL FALSE, 2, 10, 12, 16, 17, 26, 27, 31, 36, 42, 43, 46, 48, 51, 54, 55, 57, 58, 64, 65, 69–72, 75, 79, 81, 82, 84 EGL FOREVER, 69 EGL GL COLORSPACE, 32, 33, 35, 36, 40, 44 EGL GL COLORSPACE LINEAR, 33 EGL GL COLORSPACE SRGB, 33 EGL GL RENDERBUFFER, 73–76 EGL GL TEXTURE 2D, 73–76 EGL GL TEXTURE 3D, 73–77 EGL GL TEXTURE CUBE MAP NEGATIVE X, 73, 74 EGL GL TEXTURE CUBE MAP NEGATIVE Y, 73, 74 EGL GL TEXTURE CUBE MAP NEGATIVE Z, 73, 74 EGL GL TEXTURE CUBE MAP POSITIVE X, 73, 74 EGL GL TEXTURE CUBE MAP POSITIVE Y, 73, 74 EGL GL TEXTURE CUBE MAP POSITIVE Z, 73, 74 EGL GL TEXTURE LEVEL, 73, 75– 77 EGL GL TEXTURE ZOFFSET, 73, 75, 77 EGL GREEN SIZE, 20, 21, 29, 30, 38, 47 EGL HEIGHT, 35–37, 43, 44 EGL HORIZONTAL RESOLUTION, 44, 45 EGL IMAGE PRESERVED, 75, 77, 78 EGL KHR cl event2, 3, 104, 107 EGL KHR client get all proc addresses, 105, 107 EGL KHR create context, 105, 107

EGL 1.5 - August 27, 2014

INDEX

111

EGL KHR fence sync, 61, 104, 107 EGL KHR get all proc addresses, 105, 107 EGL KHR gl * image, 107 EGL KHR gl colorspace, 105, 107 EGL KHR gl renderbuffer image, 105 EGL KHR gl texture 2D image, 105 EGL KHR gl texture 3D image, 105 EGL KHR gl texture cubemap image, 105 EGL KHR image base, 104, 107 EGL KHR lock surface3, 3 105, EGL KHR surfaceless context, 107 EGL KHR wait sync, 61, 104, 107 EGL LARGEST PBUFFER, 35, 36, 43–45 EGL LEVEL, 20, 25, 27, 29, 30, 98, 106 EGL LOSE CONTEXT ON RESET, 55 EGL LUMINANCE BUFFER, 21, 30 EGL LUMINANCE SIZE, 20, 21, 29, 30 EGL MATCH NATIVE PIXMAP, 27– 29, 31, 40, 96, 100, 101 EGL MAX PBUFFER HEIGHT, 20, 25, 28 EGL MAX PBUFFER PIXELS, 20, 25, 28 EGL MAX PBUFFER WIDTH, 20, 25, 28 EGL MAX SWAP INTERVAL, 20, 25, 29, 30, 81 EGL MIN SWAP INTERVAL, 20, 26, 29, 30, 81 EGL MIPMAP LEVEL, 42–45, 48 EGL MIPMAP TEXTURE, 35–39, 44, 45, 48 EGL MULTISAMPLE RESOLVE, 23,

42–45, 98 EGL MULTISAMPLE RESOLVE BOX, 42, 43, 45 EGL MULTISAMPLE RESOLVE BOX BIT, 23, 43 EGL MULTISAMPLE RESOLVE DEFAULT, 42, 43, 45 EGL NATIVE RENDERABLE, 20, 24, 29, 30 EGL NATIVE VISUAL ID, 20, 24, 28 EGL NATIVE VISUAL TYPE, 20, 24, 28–30 EGL NO CONTEXT, 12, 50, 51, 55, 56, 59–61, 68, 70, 72, 76, 83 EGL NO DISPLAY, 2, 15, 16, 18, 19, 59, 62, 99, 105 EGL NO IMAGE, 75 EGL NO RESET NOTIFICATION, 55 EGL NO SURFACE, 34, 36, 38, 41, 59, 60, 62, 83 EGL NO SYNC, 68 EGL NO TEXTURE, 36, 37, 42, 48, 49 EGL NON CONFORMANT CONFIG, 24, 28 EGL NONE, 15, 24, 25, 27–29, 32, 35, 38, 40, 51, 55, 61, 63, 66, 73, 75 EGL NOT INITIALIZED, 12, 14, 16, 18, 19, 26, 60 EGL OPENGL API, 50, 52, 53, 101 EGL OPENGL BIT, 24 EGL OPENGL ES2 BIT, 24, 37, 56, 96 EGL OPENGL ES3 BIT, 24, 37, 56 EGL OPENGL ES API, 50–52, 64, 101 EGL OPENGL ES BIT, 24, 29, 37, 56 EGL OPENVG API, 50 EGL OPENVG BIT, 24

EGL 1.5 - August 27, 2014

INDEX

112

EGL OPENVG IMAGE, 38 EGL PBUFFER BIT, 23, 26 EGL PIXEL ASPECT RATIO, 44, 45, 99 EGL PIXMAP BIT, 23, 41 EGL READ, 62 EGL RED SIZE, 20, 21, 25, 28–30, 38, 47 EGL RENDER BUFFER, 32, 33, 44, 45, 63, 102 EGL RENDERABLE TYPE, 20, 21, 23–25, 29, 30, 37, 56, 96 EGL RGB BUFFER, 21, 29, 30 EGL SAMPLE BUFFERS, 20, 22, 29, 30, 60 EGL SAMPLES, 20, 22, 29, 30 EGL SIGNALED, 67 EGL SINGLE BUFFER, 32, 45, 63 EGL SLOW CONFIG, 24, 28 EGL STENCIL SIZE, 20, 22, 29, 30 EGL SUCCESS, 12, 14, 84, 101 EGL SURFACE TYPE, 20, 23, 26, 28– 30, 34, 41, 43, 96, 98 EGL SWAP BEHAVIOR, 23, 42–45, 79, 98, 100 EGL SWAP BEHAVIOR PRESERVED BIT, 23, 43, 100 EGL SYNC CL EVENT, 67, 68, 71 EGL SYNC CL EVENT COMPLETE, 67, 68 EGL SYNC CONDITION, 67, 68, 71 EGL SYNC FENCE, 66–68, 71 EGL SYNC FLUSH COMMANDS BIT, 69 EGL SYNC PRIOR COMMANDS COMPLETE, 67 EGL SYNC STATUS, 67, 68, 71 EGL SYNC TYPE, 67, 68, 71 EGL TEXTURE 2D, 36, 47

EGL TEXTURE FORMAT, 35–38, 42, 44, 45, 47–49 EGL TEXTURE RGB, 36 EGL TEXTURE RGBA, 36 EGL TEXTURE TARGET, 35–38, 42, 44, 45, 47 EGL TIMEOUT EXPIRED, 69 EGL TRANSPARENT BLUE VALUE, 20, 25, 28–30 EGL TRANSPARENT GREEN VALUE, 20, 25, 28–30 EGL TRANSPARENT RED VALUE, 20, 25, 28–30 EGL TRANSPARENT RGB, 25 EGL TRANSPARENT TYPE, 20, 25, 28–30 EGL TRUE, 2, 3, 12, 16, 17, 20, 26, 31, 36, 39, 45, 48, 54, 55, 64, 65, 70–72, 75, 77, 78, 83 EGL UNKNOWN, 45 EGL UNSIGNALED, 67 EGL VENDOR, 18 EGL VERSION, 18, 19 EGL VERTICAL RESOLUTION, 44, 45 EGL VG ALPHA FORMAT, 23, 32– 36, 38, 40, 44, 97, 100 EGL VG ALPHA FORMAT NONPRE, 33, 34, 97 EGL VG ALPHA FORMAT PRE, 23, 34, 97 EGL VG ALPHA FORMAT PRE BIT, 23, 96 EGL VG COLORSPACE, 23, 32–36, 38, 40, 44, 97 EGL VG COLORSPACE LINEAR, 23, 33, 97 EGL VG COLORSPACE LINEAR BIT, 23, 96

EGL 1.5 - August 27, 2014

INDEX

113

EGL VG COLORSPACE sRGB, 33, 97 EGL WIDTH, 35–37, 43, 44 EGL WINDOW BIT, 23, 28, 29, 34 EGLAttrib, 3, 106 eglBindAPI, 50, 51, 55, 63–65, 83, 101, 106 eglBindTexImage, 46–49, 73, 77 EGLBoolean, 2, 12, 24 eglChooseConfig, 19, 27, 30–32, 35, 38, 40, 51, 96 EGLClientBuffer, 38, 73, 75 eglClientWaitSync, 3, 66, 69–72 EGLConfig, 4, 5, 13, 19, 20, 22–32, 34, 35, 37, 38, 40, 41, 43, 44, 49, 56, 60, 63, 81, 98, 101 EGLContext, 3, 10, 13, 51, 75, 76 eglCopyBuffers, 6, 10, 22, 47, 50, 80– 82, 101, 102 eglCreateContext, 50, 51, 55, 57, 96, 101, 106 eglCreateImage, 3, 72–75, 77, 90, 105, 106 eglCreatePbufferFromClientBuffer, 37, 38, 58, 73, 77, 98, 100 eglCreatePbufferSurface, 25, 35, 36, 38, 40, 43 eglCreatePixmapSurface, 41 eglCreatePlatformPixmapSurface, 3, 40, 41 eglCreatePlatformWindowSurface, 3, 32, 34–36, 40, 41 eglCreateSync, 3, 66, 68, 70, 72, 105 eglCreateWindowSurface, 35, 101 eglDestroyContext, 10, 57, 61, 99 eglDestroyImage, 78, 79 eglDestroySurface, 39, 41, 42, 62, 99 eglDestroySync, 72 EGLDisplay, 3–5, 11, 13–18, 31, 50, 59, 62, 66, 68, 70, 73, 75, 76, 79,

84, 99 eglGetConfigAttrib, 31, 100 eglGetConfigs, 26, 27, 31 eglGetCurrentContext, 50, 61, 62, 66, 68–70, 99 eglGetCurrentDisplay, 50, 62, 68 eglGetCurrentSurface, 50, 62, 99 eglGetDisplay, 15, 16 eglGetError, 12, 14, 83, 84, 101 eglGetPlatformDisplay, 3, 15 eglGetProcAddress, 82, 83, 101, 102, 105 eglGetSyncAttrib, 3, 71 EGLImage, 3, 73, 77–79, 106 eglInitialize, 16–18 EGLint, 3, 101 eglMakeCurrent, 10, 17, 50, 58–60, 83, 98, 102, 105 EGLNativeDisplayType, 98 EGLNativePixmapType, 13, 14 EGLNativeWindowType, 14 eglQueryAPI, 51, 64 eglQueryContext, 32, 33, 45, 63, 64, 102 eglQueryString, 2, 11, 18, 62, 82, 105 eglQuerySurface, 36, 43, 45, 46, 63 eglReleaseTexImage, 46–49 eglReleaseThread, 14, 17, 83, 84 EGLSurface, 3–5, 10, 13, 19, 25, 32, 34, 40–43, 46, 48, 49, 51, 58, 73, 98, 101, 105 eglSurfaceAttrib, 22, 23, 42, 43, 45, 79 eglSwapBuffers, 6, 10, 22, 25, 26, 32, 43, 45, 47, 50, 79–81, 101, 102 eglSwapInterval, 25, 26, 50, 81, 82, 102, 106 EGLSync, 3 eglTerminate, 16, 17, 42, 57, 61, 62, 99, 100 EGLTime, 3

EGL 1.5 - August 27, 2014

INDEX

114

eglWaitClient, 9, 50, 64, 102 eglWaitGL, 64 eglWaitNative, 9, 50, 65, 102 eglWaitSync, 66, 67, 70–72 EXT, 106 GL ARB compatibility, 53 GL ARB robustness, 55 GL ARB sync, 67 GL BLUE BITS, 21 GL CONTEXT PROFILE MASK, 54 GL EXT robustness, 55 GL EXTENSIONS, 82 GL FRAMEBUFFER ATTACHMENT COLOR ENCODING, 33 GL FRAMEBUFFER SRGB, 33 GL GENERATE MIPMAP, 48 GL GREEN BITS, 21 GL INVALID OPERATION, 82 GL KHR debug, 54 GL LINEAR, 33 GL LOSE CONTEXT ON RESET ARB, 55 GL MAJOR VERSION, 53 GL MINOR VERSION, 53 GL NO RESET NOTIFICATION ARB, 55 GL OES EGL image, 78 GL OES EGL sync, 67 GL OES surfaceless context, 60 GL RED BITS, 21 GL RENDERBUFFER, 75 GL SRGB, 33 GL TEXTURE 2D, 8, 73 GL TEXTURE 3D, 8, 73 GL TEXTURE BASE LEVEL, 48 GL TEXTURE CUBE MAP, 8, 73 GL TRUE, 48 GL VERSION, 53

glBindBuffer, 8 glBindTexture, 8 glCopyTexImage2D, 48 glDeleteTextures, 78 glFinish, 9, 47, 61, 64 glFlush, 47, 80 glGetIntegerv, 53 glGetString, 53, 82 glMapBuffer, 58 glReadPixels, 47, 59 glScissor, 60 glTexImage, 46, 49 glTexImage2D, 48, 49 glViewport, 60 int, 3 intptr t, 3 VG EXTENSIONS, 82 VG KHR EGL sync, 67 VG lRGBA 8888, 38 vgDestroyImage, 39 vgFinish, 9, 64 vgFlush, 80 vgGetString, 82 VGImage, 37–39, 90 VGImageFormat, 33, 38

EGL 1.5 - August 27, 2014

EGL 1.5 Specification — EGL 1.5 Specification

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