[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.

v2: add _NEW_COLOR flag in _mesa_update_state_locked()

Fixes piglit fbo-alphatest-nocolor-ff failures with Gallium drivers.
---
 src/mesa/main/ff_fragment_shader.cpp |    6 ++++++
 src/mesa/main/state.c                |    2 +-
 2 files changed, 7 insertions(+), 1 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 */
diff --git a/src/mesa/main/state.c b/src/mesa/main/state.c
index 80fd03b..bed6c89 100644
--- a/src/mesa/main/state.c
+++ b/src/mesa/main/state.c
@@ -589,7 +589,7 @@ _mesa_update_state_locked( struct gl_context *ctx )
    if (ctx->FragmentProgram._MaintainTexEnvProgram) {
       prog_flags |= (_NEW_BUFFERS | _NEW_TEXTURE | _NEW_FOG |
 		     _NEW_ARRAY | _NEW_LIGHT | _NEW_POINT | _NEW_RENDERMODE |
-		     _NEW_PROGRAM | _NEW_FRAG_CLAMP);
+		     _NEW_PROGRAM | _NEW_FRAG_CLAMP | _NEW_COLOR);
    }
    if (ctx->VertexProgram._MaintainTnlProgram) {
       prog_flags |= (_NEW_ARRAY | _NEW_TEXTURE | _NEW_TEXTURE_MATRIX |
-- 
1.7.3.4