Add "sample locations" feature to GrProcessor

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 48 matching lines @@
 
 GrGLSLFragmentShaderBuilder::FragPosKey
 GrGLSLFragmentShaderBuilder::KeyForFragmentPosition(const GrRenderTarget* dst) {
     if (kTopLeft_GrSurfaceOrigin == dst->origin()) {
         return kTopLeftFragPosRead_FragPosKey;
     } else {
         return kBottomLeftFragPosRead_FragPosKey;
     }
 }
 
+static const char* sampleOffsetArrays[] = {
+    "deviceSpaceSampleOffsets",
+    "windowSpaceSampleOffsets"
+};
+
+GR_STATIC_ASSERT(0 == GrGLSLFPFragmentBuilder::kSkiaDevice_Coordinates);
+GR_STATIC_ASSERT(1 == GrGLSLFPFragmentBuilder::kGLSLWindow_Coordinates);
+GR_STATIC_ASSERT(SK_ARRAY_COUNT(sampleOffsetArrays) ==
+                 GrGLSLFPFragmentBuilder::kLast_Coordinates + 1);
+
 GrGLSLFragmentShaderBuilder::GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program,
                                                          uint8_t fragPosKey)
     : GrGLSLFragmentBuilder(program)
     , fSetupFragPosition(false)
     , fTopLeftFragPosRead(kTopLeftFragPosRead_FragPosKey == fragPosKey)
     , fHasCustomColorOutput(false)
     , fCustomColorOutputIndex(-1)
     , fHasSecondaryOutput(false)
+    , fUsedSampleOffsetArrays(0)
     , fHasInitializedSampleMask(false) {
     fSubstageIndices.push_back(0);
 #ifdef SK_DEBUG
     fUsedProcessorFeatures = GrProcessor::kNone_RequiredFeatures;
     fHasReadDstColor = false;
 #endif
 }
 
-bool GrGLSLFragmentShaderBuilder::hasFragmentPosition() const {
-    return 0 != fProgramBuilder->header().fFragPosKey;
-}
-
 bool GrGLSLFragmentShaderBuilder::enableFeature(GLSLFeature feature) {
     switch (feature) {
         case kStandardDerivatives_GLSLFeature: {
             if (!fProgramBuilder->glslCaps()->shaderDerivativeSupport()) {
                 return false;
             }
             const char* extension = fProgramBuilder->glslCaps()->shaderDerivativeExtensionString();
             if (extension) {
                 this->addFeature(1 << kStandardDerivatives_GLSLFeature, extension);
             }
@@ skipping 23 matching lines @@
     SkString coords2D("coords2D");
     if (0 != index) {
         coords2D.appendf("_%i", index);
     }
     this->codeAppendf("\tvec2 %s = %s.xy / %s.z;",
                       coords2D.c_str(), coords[index].c_str(), coords[index].c_str());
     return coords2D;
 }
 
 const char* GrGLSLFragmentShaderBuilder::fragmentPosition() {
-    SkASSERT(this->hasFragmentPosition());
+    SkASSERT(fProgramBuilder->canReadFragmentPosition());
     SkDEBUGCODE(fUsedProcessorFeatures |= GrProcessor::kFragmentPosition_RequiredFeature;)
 
     const GrGLSLCaps* glslCaps = fProgramBuilder->glslCaps();
     // We only declare "gl_FragCoord" when we're in the case where we want to use layout qualifiers
     // to reverse y. Otherwise it isn't necessary and whether the "in" qualifier appears in the
     // declaration varies in earlier GLSL specs. So it is simpler to omit it.
     if (fTopLeftFragPosRead) {
         fSetupFragPosition = true;
         return "gl_FragCoord";
     } else if (const char* extension = glslCaps->fragCoordConventionsExtensionString()) {
@@ skipping 27 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::appendOffsetToSample(const char* sampleIdx, Coordinates coords) {
+    SkASSERT(fProgramBuilder->canUseSampleLocations());

[Chris Dalton, 2016/02/29 20:52:50]

Is an assert here good enough? Or do we prefer an actual check,followed by
emitting "vec2(0)" if sample locations are not supported?

[bsalomon, 2016/03/01 14:28:55]

An assert seems fine.

+    SkDEBUGCODE(fUsedProcessorFeatures |= GrProcessor::kSampleLocations_RequiredFeature);
+    this->codeAppendf("%s[%s]", sampleOffsetArrays[coords], sampleIdx);
+    fUsedSampleOffsetArrays |= (1 << coords);
+}
+
 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) {
@@ skipping 116 matching lines @@
     const GrGLSLCaps& caps = *fProgramBuilder->glslCaps();
     return caps.mustDeclareFragmentShaderOutput() ? DeclaredSecondaryColorOutputName()
                                                   : "gl_SecondaryFragColorEXT";
 }
 
 void GrGLSLFragmentShaderBuilder::onFinalize() {
     fProgramBuilder->varyingHandler()->getFragDecls(&this->inputs(), &this->outputs());
     GrGLSLAppendDefaultFloatPrecisionDeclaration(kDefault_GrSLPrecision,
                                                  *fProgramBuilder->glslCaps(),
                                                  &this->precisionQualifier());
+    if (fUsedSampleOffsetArrays & (1 << kSkiaDevice_Coordinates)) {
+        this->defineSampleOffsetArray(sampleOffsetArrays[kSkiaDevice_Coordinates],
+                                      SkMatrix::MakeTrans(-0.5f, -0.5f));
+    }
+    if (fUsedSampleOffsetArrays & (1 << kGLSLWindow_Coordinates)) {
+        SkMatrix m;
+        m.setScale(1, -1);
+        m.preTranslate(-0.5f, -0.5f);
+        this->defineSampleOffsetArray(sampleOffsetArrays[kGLSLWindow_Coordinates], m);
+    }
+}
+
+void GrGLSLFragmentShaderBuilder::defineSampleOffsetArray(const char* name, const SkMatrix& m) {
+    const GrPipeline& pipeline = fProgramBuilder->pipeline();
+    const GrRenderTargetPriv& rtp = pipeline.getRenderTarget()->renderTargetPriv();
+    int effectiveSampleCnt = rtp.getEffectiveSampleCount(pipeline.getStencil());
+    SkSTArray<16, SkPoint, true> offsets;
+    offsets.push_back_n(effectiveSampleCnt);
+    m.mapPoints(offsets.begin(), rtp.getSampleLocations(pipeline.getStencil()), effectiveSampleCnt);
+    this->definitions().append("const ");
+    if (fProgramBuilder->glslCaps()->usesPrecisionModifiers()) {
+        this->definitions().append("highp ");
+    }
+    this->definitions().appendf("vec2 %s[] = vec2[](", name);
+    for (int i = 0; i < effectiveSampleCnt; ++i) {
+        this->definitions().appendf("vec2(%f, %f)", offsets[i].x(), offsets[i].y());
+        this->definitions().append(i + 1 != effectiveSampleCnt ? ", " : ");\n");
+    }
 }
 
 void GrGLSLFragmentShaderBuilder::onBeforeChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 1);
     fSubstageIndices.push_back(0);
     // second-to-last value in the fSubstageIndices stack is the index of the child proc
     // at that level which is currently emitting code.
     fMangleString.appendf("_c%d", fSubstageIndices[fSubstageIndices.count() - 2]);
 }
 
 void GrGLSLFragmentShaderBuilder::onAfterChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 2);
     fSubstageIndices.pop_back();
     fSubstageIndices.back()++;
     int removeAt = fMangleString.findLastOf('_');
     fMangleString.remove(removeAt, fMangleString.size() - removeAt);
 }