If the user requested a GL_RGB texture but the driver actually allocated
an RGBA texture, the alpha values in the texture may not be defined.
If we later bind the texture as a color target and try to blend into
it with GL_DST_ALPHA or GL_ONE_MINUS_DST_ALPHA we may blend with
undefined alpha values when, in fact, the dest alpha value should be one.
So replace GL_DST_ALPHA/GL_ONE_MINUS_DST_ALPHA with GL_ONE/GL_ZERO.
Fixes the piglit fbo-blending-formats test for some GL_RGB formats
with the VMware driver. Also tested with llvmpipe.
v2: use the i-th (not j-th) render buffer's base format
---
src/mesa/state_tracker/st_atom_blend.c | 38 +++++++++++++++++++++++++---------
1 file changed, 28 insertions(+), 10 deletions(-)
diff --git a/src/mesa/state_tracker/st_atom_blend.c
b/src/mesa/state_tracker/st_atom_blend.c
index 6bb4077..6337e1c 100644
--- a/src/mesa/state_tracker/st_atom_blend.c
+++ b/src/mesa/state_tracker/st_atom_blend.c
@@ -44,10 +44,21 @@
/**
* Convert GLenum blend tokens to pipe tokens.
* Both blend factors and blend funcs are accepted.
+ * \param destBaseFormat the base format of the render target, such as
+ * GL_RGBA, GL_RGB, GL_RED, GL_ALPHA, etc.
*/
static GLuint
-translate_blend(GLenum blend)
+translate_blend(GLenum blend, GLenum destBaseFormat)
{
+ /* If we don't have destination alpha and the blend factor is either
+ * GL_DST_ALPHA or GL_ONE_MINUS_DST_ALPHA then we use
+ * PIPE_BLENDFACTOR_ONE or _ZERO instead.
+ */
+ const bool haveDstA = (destBaseFormat == GL_RGBA ||
+ destBaseFormat == GL_ALPHA ||
+ destBaseFormat == GL_INTENSITY ||
+ destBaseFormat == GL_LUMINANCE_ALPHA);
+
switch (blend) {
/* blend functions */
case GL_FUNC_ADD:
@@ -69,7 +80,7 @@ translate_blend(GLenum blend)
case GL_SRC_ALPHA:
return PIPE_BLENDFACTOR_SRC_ALPHA;
case GL_DST_ALPHA:
- return PIPE_BLENDFACTOR_DST_ALPHA;
+ return haveDstA ? PIPE_BLENDFACTOR_DST_ALPHA : PIPE_BLENDFACTOR_ONE;
case GL_DST_COLOR:
return PIPE_BLENDFACTOR_DST_COLOR;
case GL_SRC_ALPHA_SATURATE:
@@ -91,7 +102,7 @@ translate_blend(GLenum blend)
case GL_ONE_MINUS_DST_COLOR:
return PIPE_BLENDFACTOR_INV_DST_COLOR;
case GL_ONE_MINUS_DST_ALPHA:
- return PIPE_BLENDFACTOR_INV_DST_ALPHA;
+ return haveDstA ? PIPE_BLENDFACTOR_INV_DST_ALPHA : PIPE_BLENDFACTOR_ZERO;
case GL_ONE_MINUS_CONSTANT_COLOR:
return PIPE_BLENDFACTOR_INV_CONST_COLOR;
case GL_ONE_MINUS_CONSTANT_ALPHA:
@@ -208,14 +219,21 @@ update_blend( struct st_context *st )
else if (ctx->Color.BlendEnabled) {
/* blending enabled */
for (i = 0, j = 0; i < num_state; i++) {
+ const struct gl_renderbuffer *rb;
+ GLenum baseFormat;
blend->rt[i].blend_enable = (ctx->Color.BlendEnabled >> i) & 0x1;
if (ctx->Extensions.ARB_draw_buffers_blend)
j = i;
+ /* _NEW_BUFFERS */
+ /* Get the base format of the i-th render target */
+ rb = ctx->DrawBuffer->_ColorDrawBuffers[i];
+ baseFormat = rb ? rb->_BaseFormat : GL_RGBA;
+
blend->rt[i].rgb_func =
- translate_blend(ctx->Color.Blend[j].EquationRGB);
+ translate_blend(ctx->Color.Blend[j].EquationRGB, baseFormat);
if (ctx->Color.Blend[i].EquationRGB == GL_MIN ||
ctx->Color.Blend[i].EquationRGB == GL_MAX) {
@@ -225,13 +243,13 @@ update_blend( struct st_context *st )
}
else {
blend->rt[i].rgb_src_factor =
- translate_blend(ctx->Color.Blend[j].SrcRGB);
+ translate_blend(ctx->Color.Blend[j].SrcRGB, baseFormat);
blend->rt[i].rgb_dst_factor =
- translate_blend(ctx->Color.Blend[j].DstRGB);
+ translate_blend(ctx->Color.Blend[j].DstRGB, baseFormat);
}
blend->rt[i].alpha_func =
- translate_blend(ctx->Color.Blend[j].EquationA);
+ translate_blend(ctx->Color.Blend[j].EquationA, baseFormat);
if (ctx->Color.Blend[i].EquationA == GL_MIN ||
ctx->Color.Blend[i].EquationA == GL_MAX) {
@@ -241,9 +259,9 @@ update_blend( struct st_context *st )
}
else {
blend->rt[i].alpha_src_factor =
- translate_blend(ctx->Color.Blend[j].SrcA);
+ translate_blend(ctx->Color.Blend[j].SrcA, baseFormat);
blend->rt[i].alpha_dst_factor =
- translate_blend(ctx->Color.Blend[j].DstA);
+ translate_blend(ctx->Color.Blend[j].DstA, baseFormat);
}
}
}
@@ -285,7 +303,7 @@ update_blend( struct st_context *st )
const struct st_tracked_state st_update_blend = {
"st_update_blend", /* name */
{ /* dirty */
- (_NEW_COLOR | _NEW_MULTISAMPLE), /* XXX _NEW_BLEND someday? */ /* mesa
*/
+ (_NEW_BUFFERS | _NEW_COLOR | _NEW_MULTISAMPLE), /* mesa */
0, /* st */
},
update_blend, /* update */
--
1.9.1
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