Implement support for mixed sampled render targets

include/gpu/GrTypes.h

Index: include/gpu/GrTypes.h
diff --git a/include/gpu/GrTypes.h b/include/gpu/GrTypes.h
index 3f02c62bfd07aab21c647c673beef0850a782c32..fc85956288dfaa79bde9f7966fa02bddd7ceda9c 100644
--- a/include/gpu/GrTypes.h
+++ b/include/gpu/GrTypes.h
@@ -423,6 +423,32 @@ enum GrSurfaceOrigin {
 };
 
 /**
+ * Sample config clarifies the meaning of samples count.
+ * In default kUnified_GrSampleConfig sample count refers to MSAA sample count.
+ * If NV_framebuffer_mixed_samples is available and sample config is chosen to be
+ * kStencil_GrSampleConfig, sample count refers to the stencil sample count only,
+ * and the color sample count is assumed to be zero.
+ */
+enum GrSampleConfig {
+    kUnified_GrSampleConfig,
+    kStencil_GrSampleConfig,
+};
+
+/**
+ * Pipeline stage serves as a query parameter to render target's isMultisampled
+ * and numSamples methods.  It signifies whether the caller is interested in
+ * multisampling in color buffer or stencil buffer specifically, both, or any of
+ * the two.  Used by the NV_framebuffer_mixed_samples implementation.
+ */

[Chris Dalton, 2015/03/19 12:07:41]

I think this enum belongs inside the GrRenderTarget class.

+enum GrPipelineStage {
+    kColorBuffer_GrPipelineStage,
+    kStencilBuffer_GrPipelineStage,
+    kEverywhere_GrPipelineStage = kColorBuffer_GrPipelineStage,
+    kAnywhere_GrPipelineStage = kStencilBuffer_GrPipelineStage,
+    kRaster_GrPipelineStage = kStencilBuffer_GrPipelineStage

[Chris Dalton, 2015/03/19 12:07:41]

We maybe don't have to include kRaster for now. Sorry about that. It has some
extra considerations if a stencil buffer isn't attached yet...

+};
+
+/**
  * Describes a surface to be created.
  */
 struct GrSurfaceDesc {
@@ -549,6 +575,13 @@ struct GrBackendRenderTargetDesc {
      */
     int                             fSampleCnt;
     /**
+     * If fSampleCnt is > 1, which buffers are multisampled (color and stencil,
+     * or just stencil?). The default is both. Note that mixing multisampled
+     * and aliased buffers is only possible if NV_framebuffer_mixed_samples is
+     * available.
+     */
+    GrSampleConfig                  fSampleConfig;
+    /**
      * Number of bits of stencil per-pixel.
      */
     int                             fStencilBits;