Implement support for mixed sampled render targets

include/gpu/GrRenderTarget.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrRenderTarget_DEFINED
 #define GrRenderTarget_DEFINED
 
@@ skipping 13 matching lines @@
 class GrRenderTarget : virtual public GrSurface {
 public:
     SK_DECLARE_INST_COUNT(GrRenderTarget)
 
     // GrSurface overrides
     GrRenderTarget* asRenderTarget() SK_OVERRIDE { return this; }
     const GrRenderTarget* asRenderTarget() const  SK_OVERRIDE { return this; }
 
     // GrRenderTarget
     /**
-     * @return true if the surface is multisampled, false otherwise
+     * @param  pipelineStage  specifies the buffer(s) for which multisampling
+                              is queried
+     * @return true if the surface is multisampled in all of the buffers
+     *         specified by the sample config, false if any are non-MSAA
      */

[Chris Dalton, 2015/03/19 12:07:40]

Maybe pipeline stage would be better to say than buffer. For example, raster is
a pipeline stage that could be multisampled, but not a buffer... 

-    bool isMultisampled() const { return 0 != fDesc.fSampleCnt; }
+    bool isMultisampled(GrPipelineStage pipelineStage =
+                                        kEverywhere_GrPipelineStage) const {
+        return 0 != numSamples(pipelineStage);
+    }
 
     /**
-     * @return the number of samples-per-pixel or zero if non-MSAA.
+     * @param  pipelineStage  specifies the buffer(s) for which sample count
+                              is queried
+     * @return the number of samples-per-pixel or zero if any of the specified
+     *         buffers is non-MSAA.
      */
-    int numSamples() const { return fDesc.fSampleCnt; }
+    int numSamples(GrPipelineStage pipelineStage =
+                                   kEverywhere_GrPipelineStage) const {
+        if (kStencil_GrSampleConfig == fSampleConfig &&
+            kColorBuffer_GrPipelineStage == pipelineStage) {
+            return 0;
+        }
+        return fDesc.fSampleCnt;
+    }
+
+    /**
+     * @return sample config: kUnified_GrSampleConfig if both color and stencil
+               buffers are MSAA, or kStencil_GrSampleConfig if only stencil
+               buffer is MSAA.
+     */
+    GrSampleConfig sampleConfig() const {
+        return fSampleConfig;
+    }
 
     /**
      * Call to indicate the multisample contents were modified such that the
      * render target needs to be resolved before it can be used as texture. Gr
      * tracks this for its own drawing and thus this only needs to be called
      * when the render target has been modified outside of Gr. This has no
      * effect on wrapped backend render targets.
      *
      * @param rect  a rect bounding the area needing resolve. NULL indicates
      *              the whole RT needs resolving.
@@ skipping 35 matching lines @@
         kAutoResolves_ResolveType,
         kCantResolve_ResolveType,
     };
     virtual ResolveType getResolveType() const = 0;
 
     // Provides access to functions that aren't part of the public API.
     GrRenderTargetPriv renderTargetPriv();
     const GrRenderTargetPriv renderTargetPriv() const;
 
 protected:
-    GrRenderTarget(GrGpu* gpu, LifeCycle lifeCycle, const GrSurfaceDesc& desc)
+    GrRenderTarget(GrGpu* gpu, LifeCycle lifeCycle, const GrSurfaceDesc& desc,
+                   GrSampleConfig sampleConfig)
         : INHERITED(gpu, lifeCycle, desc)
+        , fSampleConfig(sampleConfig)
         , fStencilBuffer(NULL) {
         fResolveRect.setLargestInverted();
     }
 
     // override of GrResource
     void onAbandon() SK_OVERRIDE;
     void onRelease() SK_OVERRIDE;
 
 private:
     // Checked when this object is asked to attach a stencil buffer.
     virtual bool canAttemptStencilAttachment() const = 0;
 
     friend class GrRenderTargetPriv;
 
+    GrSampleConfig    fSampleConfig;
+
     GrStencilBuffer*  fStencilBuffer;
 
     SkIRect           fResolveRect;
 
     typedef GrSurface INHERITED;
 };
 
 #endif