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gltexturebuilder: Document format expectations

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Provide some details about storage and alpha handling.
This commit is contained in:
Matthias Clasen
2023-05-29 23:45:06 -04:00
parent 2bf2635635
commit 4f6d7c69a1
1 changed files with 9 additions and 0 deletions
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gdk/gdkgltexturebuilder.c
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@@ -644,6 +644,15 @@ gdk_gl_texture_builder_get_format (GdkGLTextureBuilder *self)
* The format is the preferred format the texture data should be downloaded to. The
* format must be supported by the GL version of [property@Gdk.GLTextureBuilder:context].
*
* GDK's texture download code assumes that the format corresponds to the storage
* parameters of the GL texture in an obvious way. For example, a format of
* `GDK_MEMORY_R16G16B16A16_PREMULTIPLIED` is expected to be stored as `GL_RGBA16`
* texture, and `GDK_MEMORY_G8A8` is expected to be stored as `GL_RG8` texture.
*
* GDK allows GL textures to have unpremultiplied alpha, but GSK's GL renderer can't
* currently handle such textures. Non-RGBA textures need to have swizzling parameters
* set up properly to be usable in GSK's shaders.
*
* Setting the right format is particularly useful when using high bit depth textures
* to preserve the bit depth, to set the correct value for unpremultiplied textures
* and to make sure opaque textures are treated as such.