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:
EXT_texture_snorm/fbo-blending-formats
GL_ALPHA16_SNORM
GL_ALPHA8_SNORM
GL_ALPHA_SNORM
Note: Haswell bypasses this swizzle code, so may require an independent fix
for this bug.
---
src/mesa/drivers/dri/i965/brw_wm_surface_state.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
b/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
index b1f1df1..b772ef6 100644
--- a/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
+++ b/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
@@ -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;
+ break;
case GL_RED:
case GL_RG:
case GL_RGB:
--
1.7.10.4
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