[Mesa-dev] [PATCH] mesa: fix frag shader generation for alpha test with no color buffers

[Brian Paul]

If alpha test is enabled and there's no color buffers we still need the
fragment shader to emit a color.

Fixes piglit fbo-alphatest-nocolor-ff failures with Gallium drivers.
---
 src/mesa/main/ff_fragment_shader.cpp |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/src/mesa/main/ff_fragment_shader.cpp b/src/mesa/main/ff_fragment_shader.cpp
index 2ce81fe..3d7947b 100644
--- a/src/mesa/main/ff_fragment_shader.cpp
+++ b/src/mesa/main/ff_fragment_shader.cpp
@@ -489,6 +489,12 @@ static GLuint make_state_key( struct gl_context *ctx,  struct state_key *key )
    /* _NEW_BUFFERS */
    key->num_draw_buffers = ctx->DrawBuffer->_NumColorDrawBuffers;
 
+   /* _NEW_COLOR */
+   if (ctx->Color.AlphaEnabled && key->num_draw_buffers == 0) {
+      /* if alpha test is enabled we need to emit at least one color */
+      key->num_draw_buffers = 1;
+   }
+
    key->inputs_available = (inputs_available & inputs_referenced);
 
    /* compute size of state key, ignoring unused texture units */
-- 
1.7.3.4