Implement support for KHR_blend_equation_advanced

src/gpu/GrDrawTarget.cpp

Index: src/gpu/GrDrawTarget.cpp
diff --git a/src/gpu/GrDrawTarget.cpp b/src/gpu/GrDrawTarget.cpp
index bca347dbea6edf206e0a30b53def318c554cc13d..1af3ac4ef02c56cfc869cb76a2f5d1e996d216b5 100644
--- a/src/gpu/GrDrawTarget.cpp
+++ b/src/gpu/GrDrawTarget.cpp
@@ -386,8 +386,20 @@ bool GrDrawTarget::setupDstReadIfNecessary(const GrPipelineBuilder& pipelineBuil
     if (!pipelineBuilder.willXPNeedDstCopy(*this->caps(), colorPOI, coveragePOI)) {
         return true;
     }
-    SkIRect copyRect;
+
     GrRenderTarget* rt = pipelineBuilder.getRenderTarget();
+
+    if (this->caps()->textureBarrierSupport()) {
+        if (GrTexture* rtTex = rt->asTexture()) {
+            // The render target is a texture, se we can read from it directly in the shader. The XP
+            // will be responsible to detect this situation and request a texture barrier.
+            dstCopy->setTexture(rtTex);
+            dstCopy->setOffset(0, 0);
+            return true;
+        }
+    }
+
+    SkIRect copyRect;
     pipelineBuilder.clip().getConservativeBounds(rt, &copyRect);
 
     if (drawBounds) {
@@ -1067,6 +1079,7 @@ void GrDrawTargetCaps::reset() {
 
     fUseDrawInsteadOfClear = false;
 
+    fBlendEquationSupport = kBasic_BlendEquationSupport;
     fMapBufferFlags = kNone_MapFlags;
 
     fMaxRenderTargetSize = 0;
@@ -1098,6 +1111,7 @@ GrDrawTargetCaps& GrDrawTargetCaps::operator=(const GrDrawTargetCaps& other) {
 
     fUseDrawInsteadOfClear = other.fUseDrawInsteadOfClear;
 
+    fBlendEquationSupport = other.fBlendEquationSupport;
     fMapBufferFlags = other.fMapBufferFlags;
 
     fMaxRenderTargetSize = other.fMaxRenderTargetSize;
@@ -1184,6 +1198,18 @@ SkString GrDrawTargetCaps::dump() const {
     r.appendf("Max Render Target Size             : %d\n", fMaxRenderTargetSize);
     r.appendf("Max Sample Count                   : %d\n", fMaxSampleCount);
 
+    static const char* kBlendEquationSupportNames[] = {
+        "Basic",
+        "Advanced",
+        "Advanced Coherent",
+    };
+    GR_STATIC_ASSERT(0 == kBasic_BlendEquationSupport);
+    GR_STATIC_ASSERT(1 == kAdvanced_BlendEquationSupport);
+    GR_STATIC_ASSERT(2 == kAdvancedCoherent_BlendEquationSupport);
+    GR_STATIC_ASSERT(SK_ARRAY_COUNT(kBlendEquationSupportNames) == kLast_BlendEquationSupport + 1);
+
+    r.appendf("Blend Equation Support             : %s\n",
+              kBlendEquationSupportNames[fBlendEquationSupport]);
     r.appendf("Map Buffer Support                 : %s\n",
               map_flags_to_string(fMapBufferFlags).c_str());