kc3-lang/angle/extensions/EGL_ANGLE_experimental_present_path.txt

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• Hash : 2a63b3f8
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  Date : 2016-02-08T12:29:08
  

  Re-land "Implement EGL_experimental_present_path_angle"
  
  - Re-land with clang fix.
  
  This allows ANGLE to render directly onto a D3D swapchain in the correct
  orientation when using the D3D11 renderer.
  
  The trick is to add an extra uniform to each shader which takes either
  the value +1.0 or -1.0. When rendering to a texture, ANGLE sets this
  value to -1.0. When rendering to the default framebuffer, ANGLE sets
  this value to +1.0. ANGLE multiplies vertex positions by this value in
  the VS to invert rendering when appropriate. It also corrects other
  state (e.g. viewport/scissor rect) and shader built-in values
  (e.g. gl_FragCoord).
  
  This saves a substantial amount of GPU time and lowers power
  consumption. For example, the old method (where ANGLE renders all
  content onto an offscreen texture, and then copies/inverts this onto the
  swapchain at eglSwapBuffers() time) uses about 20% of the GPU each frame
  on a Lumia 630.
  
  Verification:
  + dEQP GL ES2 tests pass when "present path fast" is enabled
  + all ANGLE_end2end_tests pass when "present path fast" is enabled
  
  BUG=angleproject:1219
  
  Change-Id: I56b339897828753a616d7bae837a2f354dba9c63
  Reviewed-on: https://chromium-review.googlesource.com/326730
  Tryjob-Request: Austin Kinross <aukinros@microsoft.com>
  Reviewed-by: Corentin Wallez <cwallez@chromium.org>
  Reviewed-by: Geoff Lang <geofflang@chromium.org>
  

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• extensions/EGL_ANGLE_experimental_present_path.txt

• Name
  
      ANGLE_experimental_present_path
  
  Name Strings
  
      EGL_ANGLE_experimental_present_path
  
  Contributors
  
      Austin Kinross
  
  Contacts
  
      Austin Kinross (aukinros 'at' microsoft 'dot' com)
  
  Status
  
      Experimental
  
  Version
  
      Version 1, Jan 22 2016
  
  Number
  
      EGL Extension #XXX
  
  Extension Type
  
      EGL display extension
  
  Dependencies
  
      Requires ANGLE_platform_angle_d3d.
  
      Written against the wording of EGL 1.4 as modified by
      ANGLE_platform_angle_d3d.
  
  Overview
  
      This extension exposes an optimized, but potentially non-conformant,
      rendering path for ANGLE's D3D11 renderer on Windows.
  
  New Types
  
      None
  
  New Procedures and Functions
  
      None
  
  New Tokens
  
      Accepted as an attribute name in the <attrib_list> argument of
      eglGetPlatformDisplayEXT:
  
          EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE      0x33A4
  
      Accepted as values for the EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE attribute:
  
          EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE 0x33A9
          EGL_EXPERIMENTAL_PRESENT_PATH_COPY_ANGLE 0x33AA
  
  Additions to the EGL Specification
  
      None.
  
  New Behavior
  
      To request a display that enables this optimized rendering path,
      the value of EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE should be set to
      EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE. Setting this value may impact
      OpenGL ES conformance (see Issue 1 below).
  
      The only valid values for the attribute
      EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE are
      EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE and
      EGL_EXPERIMENTAL_PRESENT_PATH_COPY_ANGLE. If any other value is specified
      then an EGL_BAD_ATTRIBUTE error is generated and EGL_NO_DISPLAY is
      returned.
  
      If a value for EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE is specified and
      EGL_PLATFORM_ANGLE_TYPE_ANGLE is not set to
      EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE then an EGL_BAD_ATTRIBUTE error is
      generated and EGL_NO_DISPLAY is returned.
  
  	If the attribute EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE
      is unspecified then it is implicitly set to
      EGL_EXPERIMENTAL_PRESENT_PATH_COPY_ANGLE.
  
  Issues
  
      1) Does setting EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE to be
         EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE maintain OpenGL ES
         conformance?
  
         RESOLVED: Not necessarily, that is implementation-specific. Check then
         EGL_CONFORMANT attribute to see if the implementation supports any
         conformant EGL configs when EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE
         is specified.
  
  Revision History
  
      Version 1, Jan 22 2016 (Austin Kinross)
        - Initial draft

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