Implement support for mixed sampled render targets

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index b7901400fbd68c132c4b448e20874b9bb64ba291..f819117377397bb9e7d4e9d960cddcc5110f216e 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -350,6 +350,9 @@ void GrGLGpu::onResetContext(uint32_t resetBits) {
         if (this->caps()->pathRenderingSupport()) {
             this->glPathRendering()->resetContext();
         }
+        if (this->glCaps().fbMixedSamplesSupport()) {
+            GL_CALL(CoverageModulation(GR_GL_RGBA));

[Chris Dalton, 2015/03/12 07:43:35]

Let's verify there isn't a performance penalty to leaving this always enabled.
If there is, we will want to only enable as needed (at the same time we
enable/disable MULTISAMPLE).

Also, I don't think this belongs under PathRendering. I'd probably put it under
kBlend_GrGLBackendState, or _maybe_ kMSAAEnable_GrGLBackendState.

[Chris Dalton, 2015/03/12 08:04:52]

One more thing:

The coverage modulation we use may depend on the blending mode. Premultiplied
alpha would use GL_RGBA, whereas not-premultiplied alpha would need GL_ALPHA.
Have you thought this through and figured that GL_RGBA is always the correct
mode for skia? If not, Skia has already solved this problem for their own
coverage modulation so we chould just copy how they do it.

[vbuzinov, 2015/03/13 13:37:22]

1-Done. 2-Not done

+        }
     }
 
     // we assume these values
@@ -447,6 +450,7 @@ GrRenderTarget* GrGLGpu::onWrapBackendRenderTarget(const GrBackendRenderTargetDe
     GrGLuint fboID = static_cast<GrGLuint>(wrapDesc.fRenderTargetHandle);
     idDesc.fRenderFBO.reset(SkNEW_ARGS(GrGLFBO, (fboID)));
     idDesc.fMSColorRenderbufferID = 0;
+    idDesc.fSampleConfig = wrapDesc.fSampleConfig;
     idDesc.fLifeCycle = GrGpuResource::kWrapped_LifeCycle;
 
     GrSurfaceDesc desc;
@@ -794,6 +798,7 @@ static bool renderbuffer_storage_msaa(GrGLContext& ctx,
     switch (ctx.caps()->msFBOType()) {
         case GrGLCaps::kDesktop_ARB_MSFBOType:
         case GrGLCaps::kDesktop_EXT_MSFBOType:
+        case GrGLCaps::kStencil_MSFBOType:
         case GrGLCaps::kES_3_0_MSFBOType:
             GL_ALLOC_CALL(ctx.interface(),
                             RenderbufferStorageMultisample(GR_GL_RENDERBUFFER,
@@ -828,6 +833,9 @@ bool GrGLGpu::createRenderTargetObjects(const GrSurfaceDesc& desc, bool budgeted
     idDesc->fMSColorRenderbufferID = 0;
     idDesc->fLifeCycle = budgeted ? GrGpuResource::kCached_LifeCycle :
                                     GrGpuResource::kUncached_LifeCycle;
+    idDesc->fSampleConfig = GrGLCaps::kStencil_MSFBOType ==
+                            this->glCaps().msFBOType() ? kStencil_GrSampleConfig :
+                                                         kUnified_GrSampleConfig;
 
     GrGLenum status;
 
@@ -1147,7 +1155,7 @@ bool GrGLGpu::createStencilBufferForRenderTarget(GrRenderTarget* rt, int width,
     SkASSERT(width >= rt->width());
     SkASSERT(height >= rt->height());
 
-    int samples = rt->numSamples();
+    int samples = rt->numSamples(kStencil_GrSampleConfig);
     GrGLStencilBuffer::IDDesc sbDesc;
 
     int stencilFmtCnt = this->glCaps().stencilFormats().count();
@@ -2101,7 +2109,7 @@ void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA, bool isLineDraw)
     // Replace RT_HAS_MSAA with this definition once this driver bug is no longer a relevant concern
     #define RT_HAS_MSAA rt->isMultisampled()
 #else
-    #define RT_HAS_MSAA (rt->isMultisampled() || isLineDraw)
+    #define RT_HAS_MSAA (rt->isMultisampled(kStencil_GrSampleConfig) || isLineDraw)

[Chris Dalton, 2015/03/12 07:43:35]

This feels awkward to check the stencil. Ideally there would be way to ask "Do
you have multisampling anywhere?"

Also don't forget to fix the line above in the #if 0

 #endif
 
     if (kGL_GrGLStandard == this->glStandard()) {