Commit 8059c2ea authored by Carl Worth's avatar Carl Worth

i965: Use swizzles to force R, G, and B to 0.0 for ALPHA textures.

Similar to the previous commit, we may be using a texture with actual RGBA
storage for the GL_ALPHA format, so force the color values to 0.0.

This commit fixes the following piglit (sub) tests:


Note: Haswell bypasses this swizzle code, so may require an independent fix
for this bug.
Reviewed-by: Eric Anholt's avatarEric Anholt <>
parent 33599433
......@@ -729,11 +729,18 @@ brw_get_texture_swizzle(const struct gl_texture_object *t)
/* For a format with no alpha channel, force the alpha result to
* 1.0. (This allows for an RGBA texture to be used for an RGB
* format, for example).
/* If the texture's format is alpha-only, force R, G, and B to
* 0.0. Similarly, if the texture's format has no alpha channel,
* force the alpha value read to 1.0. This allows for the
* implementation to use an RGBA texture for any of these formats
* without leaking any unexpected values.
switch (img->_BaseFormat) {
case GL_ALPHA:
swizzles[0] = SWIZZLE_ZERO;
swizzles[1] = SWIZZLE_ZERO;
swizzles[2] = SWIZZLE_ZERO;
case GL_RED:
case GL_RG:
case GL_RGB:
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