kc3-lang/angle/extensions/EGL_ANGLE_iosurface_client_buffer.txt

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• Author : Geoff Lang
  Date : 2019-08-05 17:02:43
  Hash : b3eeb2a4
  Message : Emulate RGB textures using BGRX IOSurfaces. When the user requests an IOSurface Pbuffer with an RGB format, emulate the missing alpha channel by clearing it to 1.0 and masking reads and writes in shaders. BUG=angleproject:3766 Change-Id: I58c992bf641d9ece0f923603f32640615150e4f3 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1737437 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org>

• extensions/EGL_ANGLE_iosurface_client_buffer.txt

• Name
  
      ANGLE_iosurface_client_buffer
  
  Name Strings
  
      EGL_ANGLE_iosurface_client_buffer
  
  Contributors
  
      Corentin Wallez
      Geoff Lang
      James Darpinian
  
  Contacts
  
      Corentin Wallez, Google Inc. (cwallez 'at' google.com)
  
  Status
  
      Draft
  
  Version
      Version 3, Aug 13, 2019
  
  Number
  
      EGL Extension #??
  
  Dependencies
  
      This extension is written against the wording of the EGL 1.4
      Specification.
  
  Overview
  
      This extension allows creating EGL surfaces from IOSurface objects.
  
  New Types
  
      None
  
  New Procedures and Functions
  
      None
  
  New Tokens
  
      Accepted in the <buftype> parameter of eglCreatePbufferFromClientBuffer:
  
          EGL_IOSURFACE_ANGLE            0x3454
          EGL_IOSURFACE_PLANE_ANGLE      0x345A
          EGL_TEXTURE_RECTANGLE_ANGLE    0x345B
          EGL_TEXTURE_TYPE_ANGLE         0x345C
          EGL_TEXTURE_INTERNAL_FORMAT_ANGLE 0x345D
  
  Additions to Chapter 3 of the EGL 1.4 Specification (EGL Functions and Errors)
  
      Replace the last sentence of paragraph 1 of Section 3.5.3 with the
      following text.
      "Currently, the only client API resources which may be bound in this
      fashion are OpenVG VGImage objects and IOSurface objects."
  
      Replace the third paragraph of Section 3.5.3 with the following text.
      "<buftype> specifies the type of buffer to be bound. The only allowed values
      of <buftype> are EGL_OPENVG_IMAGE and EGL_IOSURFACE_ANGLE".
  
      Append the following text to the fourth paragraph of Section 3.5.3.
      "When <buftype> is EGL_IOSURFACE_ANGLE, <buffer> must be a valid IOSurface
      object case into the type EGLClientBuffer."
  
      Append to the end of Section 3.5.3.
      "When <buftype> is EGL_IOSURFACE_ANGLE, <attrib_list> must contain all the
      following attributes otherwise EGL_BAD_PARAMETER is generated. The
      attributes must satisfy the following constraints otherwise
      EGL_BAD_ATTRIBUTE is generated:
        - EGL_TEXTURE_TYPE_ANGLE, and EGL_TEXTURE_INTERNAL_FORMAT_ANGLE followed
      by OpenGL enums for texture types, and texture internal format
      respectively.
        - EGL_TEXTURE_FORMAT with a value of EGL_TEXTURE_RGBA
        - EGL_WIDTH with a value between 1 and the width of <buffer>.
        - EGL_HEIGHT with a value between 1 and the height of <buffer>.
        - EGL_TEXTURE_TARGET with a value of EGL_TEXTURE_RECTANGLE_ANGLE
        - EGL_IOSURFACE_PLANE_ANGLE with a value between 0 and the number of
      planes of <buffer> (exclusive).
  
      In addition the EGL_TEXTURE_TYPE_ANGLE and
      EGL_TEXTURE_INTERNAL_FORMAT_ANGLE attributes must be one of the
      combinations listed in table egl.iosurface.formats or an
      EGL_BAD_PARAMETER is generated. The combination must also be a valid
      combinations for glTexImage2D or EGL_BAD_PARAMETER is generated."
  
      ---------------------------------------------------------------------------
      Texture Type               Texture Internal Format
      ---------------------------------------------------------------------------
      GL_UNSIGNED_BYTE           GL_RED
      GL_UNSIGNED_SHORT          GL_R16UI
      GL_UNSIGNED_BYTE           GL_RG
      GL_UNSIGNED_BYTE           GL_RGB
      GL_UNSIGNED_BYTE           GL_BGRA_EXT
      GL_HALF_FLOAT              GL_RGBA
      ---------------------------------------------------------------------------
      Table egl.iosurface.formats - Valid combinations of format, type and
      internal format for IOSurface-backed pbuffers.
      ---------------------------------------------------------------------------
  
      Append to the end of Section 3.5.3.
      "When a pbuffer is created with type EGL_IOSURFACE_ANGLE, the contents
      of the associcated IOSurface object are undefined while the pbuffer is
      bound to a client texture."
  
  Issues
  
      1. Can RGB formats be supported?
  
      RESOLVED: Support for RGB internal formats is added in version 3. Surfaces
      with an RGB format will ensure that the alpha channel of the IOSurface is
      reset to 1.0 when it is used.
  
  Revision History
  
      Version 1, 2017/12/06 - first draft.
      Version 2, 2019/04/01 - Allow MakeCurrent.
      Version 3, 2019/08/13 - Allow RGB internal formats