Add gl_SampleMask functionality to fragment builders

src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLSLFragmentShaderBuilder.h"
 #include "GrRenderTarget.h"
 #include "gl/GrGLGpu.h"
@@ skipping 56 matching lines @@
 }
 
 GrGLSLFragmentShaderBuilder::GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program,
                                                          uint8_t fragPosKey)
     : GrGLSLFragmentBuilder(program)
     , fSetupFragPosition(false)
     , fTopLeftFragPosRead(kTopLeftFragPosRead_FragPosKey == fragPosKey)
     , fHasCustomColorOutput(false)
     , fCustomColorOutputIndex(-1)
     , fHasSecondaryOutput(false)
+    , fHasInitializedSampleMask(false)
     , fHasReadDstColor(false)
     , fHasReadFragmentPosition(false) {
     fSubstageIndices.push_back(0);
 }
 
 bool GrGLSLFragmentShaderBuilder::enableFeature(GLSLFeature feature) {
     switch (feature) {
         case kStandardDerivatives_GLSLFeature: {
             if (!fProgramBuilder->glslCaps()->shaderDerivativeSupport()) {
                 return false;
@@ skipping 75 matching lines @@
             this->codePrependf("\t%svec4 %s = vec4(%s.x, %s - %s.y, 1.0, 1.0);\n",
                                precision, kCoordName, kTempName, rtHeightName, kTempName);
             this->codePrependf("%svec2 %s = gl_FragCoord.xy;", precision, kTempName);
             fSetupFragPosition = true;
         }
         SkASSERT(fProgramBuilder->fUniformHandles.fRTHeightUni.isValid());
         return kCoordName;
     }
 }
 
+void GrGLSLFragmentShaderBuilder::maskSampleCoverage(const char* mask, bool invert) {
+    const GrGLSLCaps& glslCaps = *fProgramBuilder->glslCaps();
+    if (!glslCaps.sampleVariablesSupport()) {
+        SkDEBUGFAIL("Attempted to mask sample coverage without support.");
+        return;
+    }
+    if (const char* extension = glslCaps.sampleVariablesExtensionString()) {
+        this->addFeature(1 << kSampleVariables_GLSLPrivateFeature, extension);
+    }
+    if (!fHasInitializedSampleMask) {
+        this->codePrependf("gl_SampleMask[0] = -1;");
+        fHasInitializedSampleMask = true;
+    }
+    if (invert) {
+        this->codeAppendf("gl_SampleMask[0] &= ~(%s);", mask);
+    } else {
+        this->codeAppendf("gl_SampleMask[0] &= %s;", mask);
+    }
+}
+
+void GrGLSLFragmentShaderBuilder::overrideSampleCoverage(const char* mask) {
+    const GrGLSLCaps& glslCaps = *fProgramBuilder->glslCaps();
+    if (!glslCaps.sampleMaskOverrideCoverageSupport()) {
+        SkDEBUGFAIL("Attempted to override sample coverage without support.");
+        return;
+    }
+    SkASSERT(glslCaps.sampleVariablesSupport());
+    if (const char* extension = glslCaps.sampleVariablesExtensionString()) {
+        this->addFeature(1 << kSampleVariables_GLSLPrivateFeature, extension);
+    }
+    if (this->addFeature(1 << kSampleMaskOverrideCoverage_GLSLPrivateFeature,
+                         "GL_NV_sample_mask_override_coverage")) {
+        // Redeclare gl_SampleMask with layout(override_coverage) if we haven't already.
+        fOutputs.push_back().set(kInt_GrSLType, GrShaderVar::kOut_TypeModifier,
+                                 "gl_SampleMask", 1, kHigh_GrSLPrecision,
+                                 "override_coverage");
+    }
+    this->codeAppendf("gl_SampleMask[0] = %s;", mask);
+    fHasInitializedSampleMask = true;
+}
+
 const char* GrGLSLFragmentShaderBuilder::dstColor() {
     fHasReadDstColor = true;
 
     const char* override = fProgramBuilder->primitiveProcessor().getDestColorOverride();
     if (override != nullptr) {
         return override;
     }
 
     const GrGLSLCaps* glslCaps = fProgramBuilder->glslCaps();
     if (glslCaps->fbFetchSupport()) {
@@ skipping 93 matching lines @@
 }
 
 void GrGLSLFragmentShaderBuilder::onAfterChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 2);
     fSubstageIndices.pop_back();
     fSubstageIndices.back()++;
     int removeAt = fMangleString.findLastOf('_');
     fMangleString.remove(removeAt, fMangleString.size() - removeAt);
 }