Add glCopyCompressedTextureCHROMIUM

gpu/GLES2/extensions/CHROMIUM/CHROMIUM_compressed_copy_texture.txt

+Name
+
+    CHROMIUM_copy_compressed_texture
+
+Name Strings
+
+    GL_CHROMIUM_copy_compressed_texture
+
+Version
+
+    Last Modifed Date: May 28, 2015
+
+Dependencies
+
+    OpenGL ES 2.0 is required.
+
+    GL_AMD_compressed_ATC_texture, GL_ATI_texture_compression_atitc,
+    GL_EXT_texture_compression_dxt1, GL_ANGLE_texture_compression_dxt5,
+    GL_EXT_texture_compression_s3tc and GL_OES_compressed_ETC1_RGB8_texture
+    affects the definition of this extension.
+
+Overview
+
+    This extension provides functionality for copying compressed textures. It
+    adds a new function glCompressedCopyTextureCHROMIUM that works similarily
+    to glCopyTextureCHROMIUM, but for compressed textures.
+
+    Which compressed texture formats that this extension supports depends on
+    the supported texture compression formats of the host GPU.
+
+Issues
+
+    glCompressedCopyTextureCHROMIUM will first try to copy into a compressed
+    texture of the same format as the source texture. If unsucessful, the
+    destination texture format will be changed to GL_RGBA and the texture will
+    be stored uncompressed.
+
+New Procedures and Functions
+
+    The command
+
+        void glCompressedCopyTextureCHROMIUM (GLenum target, GLenum source_id,
+                                              GLenum dest_id)
+
+    Copies the contents of a compressed texture referred to by <source_id> to
+    <dest_id> texture.
+
+    Texture level 0 is copied from the source image to level 0 of the
+    destination texture.
+
+    The internal format of the source and destination texture must be
+    compressed, and they must match. The format must be one of the following

[piman, 2015/06/12 19:50:29]

"The internal format of the source and destination texture must be compressed,
and they must match"

That's not what's implemented in the code, and that's not consistent with the
level image-creating functions (e.g. glCopyTexImage2D, glCopyTextureCHROMIUM,
glCompressedTexImage2D etc.).
Typically, what you want, and this is what's implemented, is that the call will
create/replace the level image with a new image that has the same internal
format as the source.

You don't want to have to call glCompressedTexImage2D before calling this - that
would be more appropriate for a glCompressedCopySubTextureCHROMIUM (which
doesn't create the image).

[christiank, 2015/06/15 09:42:41]

Ah yes you're right. I have now rephrased the text a bit.

+    symbolic constants: GL_ATC_RGB_AMD,
+    GL_ATC_RGBA_INTERPOLATED_ALPHA_AMD, GL_COMPRESSED_RGB_S3TC_DXT1_EXT,
+    GL_COMPRESSED_RGBA_S3TC_DXT5_EXT, GL_ETC1_RGB8_OES
+
+    <target> uses the same parameters as TexImage2D.
+
+    INVALID_OPERATION is generated if internal format of source and destination

[piman, 2015/06/12 19:50:29]

"source and destination" -> "source" per the above.

[christiank, 2015/06/15 09:42:41]

Done.

+    texture is not one of the valid formats described above.
+
+    INVALID_OPERATION is generated if internal format of source and destination
+    texture doesn't match.

[piman, 2015/06/12 19:50:29]

Please add the INVALID_OPERATION error case if the destination texture is
immutable.

[piman, 2015/06/12 19:50:30]

Remove, per the above.

[christiank, 2015/06/15 09:42:42]

Done.

+
+    INVALID_VALUE is generated if <source_id> or <dest_id> are not valid texture
+    objects.
+
+    INVALID_VALUE is generated if textures corresponding to <dest_id> have not
+    been bound as GL_TEXTURE_2D object.
+
+    INVALID_VALUE is generated if level 0 of the source texture is not defined.
+
+Errors
+
+    None.
+
+New Tokens
+
+    None.
+
+New State
+
+    None.
+
+Revision History
+
+    28/5/2015    Documented the extension.