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PojavLauncherTeam
GitHub Repository: PojavLauncherTeam/mesa
 Path: blob/21.2-virgl/docs/_extra/specs/MESA_bgra.txt
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Name

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    MESA_bgra

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Name Strings

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    GL_MESA_bgra

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Contact

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    Gert Wollny (gert.wollny 'at' collabora.com)

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Notice

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    Copyright (c) 2021 Collabora LTD 

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    Copyright (c) 2009-2013 The Khronos Group Inc. Copyright terms at

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        http://www.khronos.org/registry/speccopyright.html

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Version

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    Version 1, 2021/04/30.

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    Based on EXT_bgra version 1, modified 1997/05/19.

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Number

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    TBD

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Dependencies

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    OpenGL ES 2.0 is required.

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    Written based on the wording of the OpenGL ES 3.2 specification.

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    There are interactions with the extensions EXT_clear_texture.

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Overview

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    MESA_bgra extends the list of combinations host-memory color formats

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    with internal formats to include BGRA and BGR as acceptable formats

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    with RGB8/SRGB8 and RGBA/sRGB8_ALPHA8 as internal formats respectively.

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    This feature is of interest in virtualized environments, where the host

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    supports OpenGL ES only, and the virtualized guest is supposed to support

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    a subset of OpenGL including textures created with the format BGRA.

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IP Status

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    Open-source; freely implementable.

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Issues

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    None.

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New Procedures and Functions

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    None

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New Tokens

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   Accepted by the <format> parameter of TexImage2D and TexSubImage2D:

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       GL_BGR_EXT                                      0x80E0

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       GL_BGRA_EXT                                     0x80E1

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Additions to Chapter 8 of the GLES 3.2 Specification (Textures and Samplers)

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    Add to table 8.2 (Pixels data formats, valid combinations of format,

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    type, and unsized internalformat).

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      Format     Type            External          Internal Format 

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                                  Bytes

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                                per Pixel

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      -------------------------------------------------------------

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      BGRA      UNSIGNED_BYTE        4                   RGBA

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      BGR       UNSIGNED_BYTE        3                   RGB

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    Add to table 8.5 (Pixels data formats).

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      Format Name   Elements Meaning and Order    Target Buffer

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      -------------------------------------------------------------

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      BGR_EXT                 B, G, R                Color

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      BGRA_EXT               B, G, R, A              Color

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    Add to table 8.9 (Effective internal format correspondig to

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    external format).

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      Format        Type                          Effective

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                                                Internal format

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      -------------------------------------------------------------

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      BGRA_EXT       UNSIGNED_BYTE                  RGBA8

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      BGR_EXT        UNSIGNED_BYTE                  RGB8

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Interactions with EXT_clear_texture

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    When EXT_clear_texture is supported the accepted formats for

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    ClearTextureEXT and ClearSubTextureEXT are extended to include

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    the entries added above. 

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Revision History

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    Original draft, revision 1.0, May 4, 2021 (Gert Wollny)

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       rewrite EXT_bgra against OpenGL ES 3.2 instead of OpenGL 1,0.

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    Revision 1.1 (May 5. 2021): Add the new tokens, and fix

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       Clear*Texture function names.

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