Implement support for mixed sampled render targets

src/gpu/GrPipelineBuilder.h

Index: src/gpu/GrPipelineBuilder.h
diff --git a/src/gpu/GrPipelineBuilder.h b/src/gpu/GrPipelineBuilder.h
index ae9ca9b067b585795a921241c735833dd4f1aa0f..7685d76f3ce36beae17fc568d7bb3bc8e68714c4 100644
--- a/src/gpu/GrPipelineBuilder.h
+++ b/src/gpu/GrPipelineBuilder.h
@@ -45,7 +45,9 @@ public:
      * no GrPaint equivalents are set to default values with the exception of vertex attribute state
      * which is unmodified by this function and clipping which will be enabled.
      */
-    void setFromPaint(const GrPaint&, GrRenderTarget*, const GrClip&);
+    void setFromPaint(const GrPaint&, GrRenderTarget*, const GrClip&,
+                      GrRenderTarget::PipelineStage pipelineStage =

[Chris Dalton, 2015/03/20 07:01:45]

I think it's a little confusing to pass a parameter named 'pipelineStage' here.
It's not entirely obvious what the purpose of the parameter is just from reading
the code. I'm tryig to brainstorm for an approach I like better but am having a
hard time. Do you like any of these?

 * Give PipelineStage parameter a really descriptive name that says "pipeline
stages that need to be multisampled in order to use HWAA"
  ** What I don't like about this approach is that GrPipelineBuilder decides
whether to use HWAA, when really the calling code is who knows whether we should
use it. In the case of text, we shouldn't have to check
isMultiSampled(StencilBuffer) because we already know it's multisampled.
 * Instead of PipelineStage, add a second setFromPaint() overload with a new
parameter named 'bool useHWAA'. The original version calls this overload with
useHWAA='rt->isMultisampled() && paint.isAntiAlias()'
  ** What I don't like about this approach is that setFromPaint() seems to be
the one that should check paint.isAntiAlias()
 * instead of 'bool useHWAA', add 'bool canUseHWAA' with default value of
'rt->isMultisampled()' and setFromPaint uses 'paint.isAntiAlias() && canUseHWAA'
  ** What I don't like about this approach is that GrStencilAndCoverTextContext
has to send a bool 'true' value, which is confusing to read.
 * Instead of PipelineStage parameter, add PipelineStage member variable to
GrPipelineBuilder. kHWAntialias_StateBit becomes kAntialias_StateBit (whether or
not paint is antialiased) and isHWAntialias() returns '0 != (fFlagBits &
kAntialias_StateBit) &&
fRenderTarget->isMultisampled(fStagesThatHaveToBeMultisampledInOrderToUseHWAA)'
 * ...?

Maybe we could discuss this offline.

+                          GrRenderTarget::kEverywhere_PipelineStage);
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name Fragment Processors