On 09/16/2016 08:07 AM, Marek Olšák wrote:
On Thu, Sep 15, 2016 at 11:20 PM, Brian Paul <bri...@vmware.com> wrote:
Regardless of whether GL_MULTISAMPLE is enabled (it's enabled by default)
we should not set the alpha_to_coverage or alpha_to_one flags if the
current drawing buffer does not do MSAA.

This fixes the new piglit gl-1.3-alpha_to_coverage_nop test.
  src/mesa/state_tracker/st_atom_blend.c | 9 ++++++---
  src/mesa/state_tracker/st_context.c    | 3 ++-
  2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/mesa/state_tracker/st_atom_blend.c 
index 65de67b..222267e 100644
--- a/src/mesa/state_tracker/st_atom_blend.c
+++ b/src/mesa/state_tracker/st_atom_blend.c
@@ -265,9 +265,12 @@ update_blend( struct st_context *st )

     blend->dither = ctx->Color.DitherFlag;

-   if (ctx->Multisample.Enabled) {
-      /* unlike in gallium/d3d10 these operations are only performed
-         if msaa is enabled */
+   if (ctx->Multisample.Enabled &&
+       ctx->DrawBuffer &&

Is it possible for ctx->DrawBuffer to be NULL?

Probably not, but I'm not 100% sure. I have some memory of an extension to allow MakeCurrent(ctx!=null, fb==null) but I can't find it now. Or maybe MakeCurrent(ctx!=null, fb==null) is supposed to be generally supported now. I don't remember and will have to look.

I think the use case for MakeCurrent(ctx!=null, fb==null) is to have a context just to compile shaders, etc.

Actually, looking again now, I found the IncompleteFramebuffer object and the _mesa_get_incomplete_framebuffer() function. So it looks like that should be used to prevent the null pointer.

And we're not checking for DrawBuffer==NULL elsewhere. I can remove the check.

+       ctx->DrawBuffer->Visual.sampleBuffers > 0) {
+      /* Unlike in gallium/d3d10 these operations are only performed
+       * if both msaa is enabled and we have a multisample buffer.
+       */
        blend->alpha_to_coverage = ctx->Multisample.SampleAlphaToCoverage;
        blend->alpha_to_one = ctx->Multisample.SampleAlphaToOne;
diff --git a/src/mesa/state_tracker/st_context.c 
index ddc11a4..81b3387 100644
--- a/src/mesa/state_tracker/st_context.c
+++ b/src/mesa/state_tracker/st_context.c
@@ -166,7 +166,8 @@ void st_invalidate_state(struct gl_context * ctx, 
GLbitfield new_state)
     struct st_context *st = st_context(ctx);

     if (new_state & _NEW_BUFFERS) {
-      st->dirty |= ST_NEW_DSA |
+      st->dirty |= ST_NEW_BLEND |
+                   ST_NEW_DSA |
                     ST_NEW_FB_STATE |
                     ST_NEW_SAMPLE_MASK |
                     ST_NEW_SAMPLE_SHADING |

I guess it's OK to add a dependency on _NEW_BUFFERS, because that flag
is set the least often.

Reviewed-by: Marek Olšák <marek.ol...@amd.com>


PS: I'm also updating the check-in comment with remarks about how I stumbled across this in ETQW.


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