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 08e83ec197c59b03362d7a08a17d7005cdad2c1e..45d15e31161fccaf8513413a5a788b2b808ee9f8 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -373,6 +373,13 @@ void GrGLGpu::onResetContext(uint32_t resetBits) {
 
     if (resetBits & kMSAAEnable_GrGLBackendState) {
         fMSAAEnabled = kUnknown_TriState;
+
+        // In mixed samples mode coverage modulation allows the coverage to be converted to
+        // "opacity", which can then be blended into the color buffer to accomplish antialiasing.
+        // Enable coverage modulation suitable for premultiplied alpha colors.

[Chris Dalton, 2015/06/11 23:34:38]

// This state has no effect when not rendering to a mixed sampled target.

+        if (this->glCaps().shaderCaps()->mixedSamplesSupport()) {
+            GL_CALL(CoverageModulation(GR_GL_RGBA));
+        }
     }
 
     fHWActiveTextureUnitIdx = -1; // invalid
@@ -851,6 +858,7 @@ static bool renderbuffer_storage_msaa(const GrGLContext& ctx,
     switch (ctx.caps()->msFBOType()) {
         case GrGLCaps::kDesktop_ARB_MSFBOType:
         case GrGLCaps::kDesktop_EXT_MSFBOType:
+        case GrGLCaps::kMixedSamples_MSFBOType:
         case GrGLCaps::kES_3_0_MSFBOType:
             GL_ALLOC_CALL(ctx.interface(),
                             RenderbufferStorageMultisample(GR_GL_RENDERBUFFER,
@@ -888,6 +896,9 @@ bool GrGLGpu::createRenderTargetObjects(const GrSurfaceDesc& desc,
     idDesc->fRTFBOID = 0;
     idDesc->fTexFBOID = 0;
     idDesc->fLifeCycle = lifeCycle;
+    idDesc->fSampleConfig = (GrGLCaps::kMixedSamples_MSFBOType == this->glCaps().msFBOType() &&
+                            desc.fSampleCnt > 0) ? GrRenderTarget::kStencil_SampleConfig :
+                                                   GrRenderTarget::kUnified_SampleConfig;
 
     GrGLenum status;
 
@@ -1170,7 +1181,7 @@ bool GrGLGpu::createStencilAttachmentForRenderTarget(GrRenderTarget* rt, int wid
     SkASSERT(width >= rt->width());
     SkASSERT(height >= rt->height());
 
-    int samples = rt->numSamples();
+    int samples = rt->numStencilSamples();
     GrGLStencilAttachment::IDDesc sbDesc;
 
     int stencilFmtCnt = this->glCaps().stencilFormats().count();
@@ -1607,6 +1618,11 @@ void GrGLGpu::discard(GrRenderTarget* renderTarget) {
             SkFAIL("Should never get here.");
             break;
         case GrGLCaps::kInvalidate_InvalidateFBType:
+            if (kNVIDIA_GrGLDriver == this->glContext().driver() &&
+                this->glCaps().shaderCaps()->mixedSamplesSupport()) {

[vbuzinov, 2015/06/11 12:30:57]

The nature of glInvalidateFramebuffer bug seems to be more convoluted.  Looks
like we are getting a hang when invalidating a non-mixed-sampled FBO on
amazon.skp that is used to compute the blur effect and has a mixed-sampled FBO
as a source.  Using a broader condition here until it gets resolved.

[bsalomon, 2015/06/11 13:33:14]

Can we just disable support for framebuffer invalidation when setting up the
caps (until the issue is resolved)? That way if we were to add another code path
that uses the functionality it'd inherit the workaround.

+                // Workaround NVIDIA bug related to glInvalidateFramebuffer and mixed samples.
+                break;
+            }
             if (0 == glRT->renderFBOID()) {
                 //  When rendering to the default framebuffer the legal values for attachments
                 //  are GL_COLOR, GL_DEPTH, GL_STENCIL, ... rather than the various FBO attachment
@@ -2090,7 +2106,7 @@ void GrGLGpu::flushStencil(const GrStencilSettings& stencilSettings) {
 }
 
 void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA) {
-    SkASSERT(!useHWAA || rt->isMultisampled());
+    SkASSERT(!useHWAA || rt->isStencilBufferMultisampled());
 
     if (this->glCaps().multisampleDisableSupport()) {
         if (useHWAA) {