Name ANDROID_create_native_client_buffer Name Strings EGL_ANDROID_create_native_client_buffer Contributors Craig Donner Contact Craig Donner, Google Inc. (cdonner 'at' google.com) Status Draft Version Version 1, January 19, 2016 Number EGL Extension #XXX Dependencies Requires EGL 1.2. EGL_ANDROID_image_native_buffer and EGL_KHR_image_base are required. This extension is written against the wording of the EGL 1.2 Specification as modified by EGL_KHR_image_base and EGL_ANDROID_image_native_buffer. Overview This extension allows creating an EGLClientBuffer backed by an Android window buffer (struct ANativeWindowBuffer) which can be later used to create an EGLImage. New Types None. New Procedures and Functions EGLClientBuffer eglCreateNativeClientBufferANDROID( const EGLint *attrib_list) New Tokens EGL_NATIVE_BUFFER_USAGE_ANDROID 0x3143 EGL_NATIVE_BUFFER_USAGE_PROTECTED_BIT_ANDROID 0x00000001 EGL_NATIVE_BUFFER_USAGE_RENDERBUFFER_BIT_ANDROID 0x00000002 EGL_NATIVE_BUFFER_USAGE_TEXTURE_BIT_ANDROID 0x00000004 Changes to Chapter 3 of the EGL 1.2 Specification (EGL Functions and Errors) Add the following to section 2.5.1 "EGLImage Specification" (as modified by the EGL_KHR_image_base and EGL_ANDROID_image_native_buffer specifications), below the description of eglCreateImageKHR: "The command EGLClientBuffer eglCreateNativeClientBufferANDROID( const EGLint *attrib_list) may be used to create an EGLClientBuffer backed by an ANativeWindowBuffer struct. EGL implementations must guarantee that the lifetime of the returned EGLClientBuffer is at least as long as the EGLImage(s) it is bound to, following the lifetime semantics described below in section 2.5.2; the EGLClientBuffer must be destroyed no earlier than when all of its associated EGLImages are destroyed by eglDestroyImageKHR. is a list of attribute-value pairs which is used to specify the dimensions, format, and usage of the underlying buffer structure. If is non-NULL, the last attribute specified in the list must be EGL_NONE. Attribute names accepted in are shown in Table aaa, together with the for which each attribute name is valid, and the default value used for each attribute if it is not included in . +---------------------------------+----------------------+---------------+ | Attribute | Description | Default Value | | | | | +---------------------------------+----------------------+---------------+ | EGL_NONE | Marks the end of the | N/A | | | attribute-value list | | | EGL_WIDTH | The width of the | 0 | | | buffer data | | | EGL_HEIGHT | The height of the | 0 | | | buffer data | | | EGL_RED_SIZE | The bits of Red in | 0 | | | the color buffer | | | EGL_GREEN_SIZE | The bits of Green in | 0 | | | the color buffer | | | EGL_BLUE_SIZE | The bits of Blue in | 0 | | | the color buffer | | | EGL_ALPHA_SIZE | The bits of Alpha in | 0 | | | the color buffer | | | | buffer data | | | EGL_NATIVE_BUFFER_USAGE_ANDROID | The usage bits of | 0 | | | the buffer data | | +---------------------------------+----------------------+---------------+ Table aaa. Legal attributes for eglCreateNativeClientBufferANDROID parameter. The maximum width and height may depend on the amount of available memory, which may also depend on the format and usage flags. The values of EGL_RED_SIZE, EGL_GREEN_SIZE, and EGL_BLUE_SIZE must be non-zero and correspond to a valid pixel format for the implementation. If EGL_ALPHA_SIZE is non-zero then the combination of all four sizes must correspond to a valid pixel format for the implementation. The EGL_NATIVE_BUFFER_USAGE_ANDROID flag may include any of the following bits: EGL_NATIVE_BUFFER_USAGE_PROTECTED_BIT_ANDROID: Indicates that the created buffer must have a hardware-protected path to external display sink. If a hardware-protected path is not available, then either don't composite only this buffer (preferred) to the external sink, or (less desirable) do not route the entire composition to the external sink. EGL_NATIVE_BUFFER_USAGE_RENDERBUFFER_BIT_ANDROID: The buffer will be used to create a renderbuffer. This flag must not be set if EGL_NATIVE_BUFFER_USAGE_TEXTURE_BIT_ANDROID is set. EGL_NATIVE_BUFFER_USAGE_TEXTURE_BIT_ANDROID: The buffer will be used to create a texture. This flag must not be set if EGL_NATIVE_BUFFER_USAGE_RENDERBUFFER_BIT_ANDROID is set. Errors If eglCreateNativeClientBufferANDROID fails, NULL will be returned, no memory will be allocated, and one of the following errors will be generated: * If the value of EGL_WIDTH or EGL_HEIGHT is not positive, the error EGL_BAD_PARAMETER is generated. * If the combination of the values of EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE, and EGL_ALPHA_SIZE is not a valid pixel format for the EGL implementation, the error EGL_BAD_PARAMETER is generated. * If the value of EGL_NATIVE_BUFFER_ANDROID is not a valid combination of gralloc usage flags for the EGL implementation, or is incompatible with the value of EGL_FORMAT, the error EGL_BAD_PARAMETER is Generated. * If both the EGL_NATIVE_BUFFER_USAGE_RENDERBUFFER_BIT_ANDROID and EGL_NATIVE_BUFFER_USAGE_TEXTURE_BIT_ANDROID are set in the value of EGL_NATIVE_BUFFER_USAGE_ANDROID, the error EGL_BAD_PARAMETER is Generated." Issues 1. Should this extension define what combinations of formats and usage flags EGL implementations are required to support? RESOLVED: Partially. The set of valid color combinations is implementation-specific and may depend on additional EGL extensions, but generally RGB565 and RGBA888 should be supported. The particular valid combinations for a given Android version and implementation should be documented by that version. 2. Should there be an eglDestroyNativeClientBufferANDROID to destroy the client buffers created by this extension? RESOLVED: No. A destroy function would add several complications: a) ANativeWindowBuffer is a reference counted object, may be used outside of EGL. b) The same buffer may back multiple EGLImages, though this usage may result in undefined behavior. c) The interactions between the lifetimes of EGLImages and their EGLClientBuffers would become needlessly complex. Because ANativeWindowBuffer is a reference counted object, implementations of this extension should ensure the buffer has a lifetime at least as long as a generated EGLImage (via EGL_ANDROID_image_native_buffer). The simplest method is to increment the reference count of the buffer in eglCreateImagKHR, and then decrement it in eglDestroyImageKHR. This should ensure proper lifetime semantics. Revision History #2 (Craig Donner, April 15, 2016) - Set color formats and usage bits explicitly using additional attributes, and add value for new token EGL_NATIVE_BUFFER_USAGE_ANDROID. #1 (Craig Donner, January 19, 2016) - Initial draft.