kc3-lang/angle/extensions/EGL_ANGLE_iosurface_client_buffer.txt

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• Hash : 7b1b8a01
  Author :
  Date : 2023-09-21T20:15:29
  

  Metal: Allow using GL_RGB with either RGBA/BGRA IOSurface.
  
  Previously we only allowed GL_RGB internal format to be used with BGRA
  IOSurface and GL_RGBX8_ANGLE to be used with RGBA IOSurface
  respectively.
  
  However, there are currently many places in Chrome prefer GL_RGB to be
  able to be used with both RGBA and BGRA IOSurface.
  
  This CL allows such combinations. Instead of deducing angle::FormatID of
  the IOSurface pbuffer based on the input GL internal format & type, we
  will take into account the pixel format of the IOSurface as well.
  
  For example, when we call eglCreatePbufferFromClientBuffer with GL_RGB
  internal format attribute:
  - if IOSurface's pixel format is 'RGBA' ->
    deduced angle::FormatID is R8G8B8A8_UNORM.
  - if IOSurface's pixel format is 'BGRA' ->
    deduced angle::FormatID is B8G8R8A8_UNORM.
  
  This CL also removes GL_RGBX8_ANGLE support from Metal backend. Because
  there are many places in Chrome that use this format enum for both RGBA
  & BGRA IOSurface when the extension is available. It's redundant to
  support that since GL_RGB already covers most of the required cases.
  
  Bug: angleproject:8350
  Change-Id: I5a121a97e031a42d0779721d4348f373dfaee9a0
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4881742
  Reviewed-by: Kenneth Russell <kbr@chromium.org>
  Commit-Queue: Quyen Le <lehoangquyen@chromium.org>
  Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
  

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• 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
      Le Hoang Quyen
  
  Contacts
  
      Corentin Wallez, Google Inc. (cwallez 'at' google.com)
  
  Status
  
      Draft
  
  Version
      Version 6, Aug 25, 2020
  
  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
          EGL_IOSURFACE_USAGE_HINT_ANGLE 0x348A
  
      Accepted in the <attribute> parameter of
      eglGetConfigAttrib:
  
          EGL_BIND_TO_TEXTURE_TARGET_ANGLE 0x348D
  
  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 that matches the attribute
        EGL_BIND_TO_TEXTURE_TARGET_ANGLE as queried from eglGetConfigAttrib.
        - 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.
  
      The attribute EGL_IOSURFACE_USAGE_HINT_ANGLE may optionally be specified as
      a combination of the bits EGL_IOSURFACE_READ_HINT_ANGLE and
      EGL_IOSURFACE_WRITE_HINT_ANGLE. On the iOS Simulator platform, where
      IOSurface support is incomplete, these hints indicate whether the intent is
      to read from the IOSurface, write to it, or both. Explicitly passing 0 for
      this attribute is equivalent to setting both the read and write usage
      bits. This attribute is ignored on other platforms."
  
      ---------------------------------------------------------------------------
      Texture Type               Texture Internal Format
      ---------------------------------------------------------------------------
      GL_UNSIGNED_BYTE               GL_RED
      GL_UNSIGNED_SHORT              GL_RED
      GL_UNSIGNED_SHORT              GL_R16UI
      GL_UNSIGNED_BYTE               GL_RG
      GL_UNSIGNED_SHORT              GL_RG
      GL_UNSIGNED_BYTE               GL_RGB
      GL_UNSIGNED_BYTE               GL_RGBA
      GL_UNSIGNED_BYTE               GL_BGRA_EXT
      GL_UNSIGNED_INT_2_10_10_10_REV GL_RGB10_A2
      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."
  
      Append to the end of Table 3.1.
      ---------------------------------------------------------------------------
      Attribute                           Type    Notes
      ---------------------------------------------------------------------------
      EGL_BIND_TO_TEXTURE_TARGET_ANGLE    enum    Texture target supported by
      IOSurface-backed pbuffers.
      ---------------------------------------------------------------------------
  
  
  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
      Version 4, 2019/12/28 - Add usage hint; require TEXTURE_RECTANGLE on macOS
                              and TEXTURE_2D on iOS
      Version 5, 2020/06/30 - Allow RGB10_A2 internal formats
      Version 6, 2020/08/25 - Allow R16 and RG16 formats for P010 surfaces
      Version 7, 2023/09/19 - Allow RGBA/RGBX surfaces
  

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