Implement color filter as GrGLEffect

src/gpu/gl/GrGLProgramDesc.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLProgramDesc.h"
 #include "GrBackendEffectFactory.h"
 #include "GrDrawEffect.h"
@@ skipping 38 matching lines @@
     colorStages->reset();
     coverageStages->reset();
 
     // This should already have been caught
     SkASSERT(!(GrDrawState::kSkipDraw_BlendOptFlag & blendOpts));
 
     bool skipCoverage = SkToBool(blendOpts & GrDrawState::kEmitTransBlack_BlendOptFlag);
 
     bool skipColor = SkToBool(blendOpts & (GrDrawState::kEmitTransBlack_BlendOptFlag |
                                            GrDrawState::kEmitCoverage_BlendOptFlag));
+    int firstEffectiveColorStage = 0;
+    bool inputColorIsUsed = true;
+    if (!skipColor) {
+        firstEffectiveColorStage = drawState.numColorStages();
+        while (firstEffectiveColorStage > 0 && inputColorIsUsed) {
+            --firstEffectiveColorStage;
+            const GrEffect* effect = drawState.getColorStage(firstEffectiveColorStage).getEffect()->get();
+            inputColorIsUsed = effect->willUseInputColor();
+        }
+    }
+
+    int firstEffectiveCoverageStage = 0;
+    bool inputCoverageIsUsed = true;
+    if (!skipCoverage) {
+        firstEffectiveCoverageStage = drawState.numCoverageStages();
+        while (firstEffectiveCoverageStage > 0 && inputCoverageIsUsed) {
+            --firstEffectiveCoverageStage;
+            const GrEffect* effect = drawState.getCoverageStage(firstEffectiveCoverageStage).getEffect()->get();
+            inputCoverageIsUsed = effect->willUseInputColor();
+        }
+    }
 
     // The descriptor is used as a cache key. Thus when a field of the
     // descriptor will not affect program generation (because of the attribute
     // bindings in use or other descriptor field settings) it should be set
     // to a canonical value to avoid duplicate programs with different keys.
 
     bool requiresColorAttrib = !skipColor && drawState.hasColorVertexAttribute();
     bool requiresCoverageAttrib = !skipCoverage && drawState.hasCoverageVertexAttribute();
     // we only need the local coords if we're actually going to generate effect code
     bool requiresLocalCoordAttrib = !(skipCoverage  && skipColor) &&
                                     drawState.hasLocalCoordAttribute();
 
     bool colorIsTransBlack = SkToBool(blendOpts & GrDrawState::kEmitTransBlack_BlendOptFlag);
     bool colorIsSolidWhite = (blendOpts & GrDrawState::kEmitCoverage_BlendOptFlag) ||
-                             (!requiresColorAttrib && 0xffffffff == drawState.getColor());
+                             (!requiresColorAttrib && 0xffffffff == drawState.getColor()) ||
+                             (!inputColorIsUsed);
 
-    int numEffects = (skipColor ? 0 : drawState.numColorStages()) +
-                     (skipCoverage ? 0 : drawState.numCoverageStages());
+    int numEffects = (skipColor ? 0 : (drawState.numColorStages() - firstEffectiveColorStage)) +
+                     (skipCoverage ? 0 : (drawState.numCoverageStages() - firstEffectiveCoverageStage));
 
     size_t newKeyLength = KeyLength(numEffects);
     bool allocChanged;
     desc->fKey.reset(newKeyLength, SkAutoMalloc::kAlloc_OnShrink, &allocChanged);
     if (allocChanged || !desc->fInitialized) {
         // make sure any padding in the header is zero if we we haven't used this allocation before.
         memset(desc->header(), 0, kHeaderSize);
     }
     // write the key length
     *desc->atOffset<uint32_t, kLengthOffset>() = newKeyLength;
 
     KeyHeader* header = desc->header();
     EffectKey* effectKeys = desc->effectKeys();
 
     int currEffectKey = 0;
     bool readsDst = false;
     bool readFragPosition = false;
     bool hasVertexCode = false;
     if (!skipColor) {
-        for (int s = 0; s < drawState.numColorStages(); ++s) {
+        for (int s = firstEffectiveColorStage; s < drawState.numColorStages(); ++s) {
             effectKeys[currEffectKey++] =
                 get_key_and_update_stats(drawState.getColorStage(s), gpu->glCaps(),
                                          requiresLocalCoordAttrib, &readsDst, &readFragPosition,
                                          &hasVertexCode);
         }
     }
     if (!skipCoverage) {
-        for (int s = 0; s < drawState.numCoverageStages(); ++s) {
+        for (int s = firstEffectiveCoverageStage; s < drawState.numCoverageStages(); ++s) {
             effectKeys[currEffectKey++] =
                 get_key_and_update_stats(drawState.getCoverageStage(s), gpu->glCaps(),
                                          requiresLocalCoordAttrib, &readsDst, &readFragPosition,
                                          &hasVertexCode);
         }
     }
 
     header->fHasVertexCode = hasVertexCode || requiresLocalCoordAttrib;
     header->fEmitsPointSize = isPoints;
-    header->fColorFilterXfermode = skipColor ? SkXfermode::kDst_Mode : drawState.getColorFilterMode();
 
     // Currently the experimental GS will only work with triangle prims (and it doesn't do anything
     // other than pass through values from the VS to the FS anyway).
 #if GR_GL_EXPERIMENTAL_GS
 #if 0
     header->fExperimentalGS = gpu->caps().geometryShaderSupport();
 #else
     header->fExperimentalGS = false;
 #endif
 #endif
     bool defaultToUniformInputs = GR_GL_NO_CONSTANT_ATTRIBUTES || gpu->caps()->pathRenderingSupport();
 
     if (colorIsTransBlack) {
         header->fColorInput = kTransBlack_ColorInput;
     } else if (colorIsSolidWhite) {
         header->fColorInput = kSolidWhite_ColorInput;
     } else if (defaultToUniformInputs && !requiresColorAttrib) {
         header->fColorInput = kUniform_ColorInput;
     } else {
         header->fColorInput = kAttribute_ColorInput;
         header->fHasVertexCode = true;
     }
 
     bool covIsSolidWhite = !requiresCoverageAttrib && 0xffffffff == drawState.getCoverage();
 
     if (skipCoverage) {
         header->fCoverageInput = kTransBlack_ColorInput;
-    } else if (covIsSolidWhite) {
+    } else if (covIsSolidWhite || !inputCoverageIsUsed) {
         header->fCoverageInput = kSolidWhite_ColorInput;
     } else if (defaultToUniformInputs && !requiresCoverageAttrib) {
         header->fCoverageInput = kUniform_ColorInput;
     } else {
         header->fCoverageInput = kAttribute_ColorInput;
         header->fHasVertexCode = true;
     }
 
     if (readsDst) {
         SkASSERT(NULL != dstCopy || gpu->caps()->dstReadInShaderSupport());
@@ skipping 42 matching lines @@
     // Here we deal with whether/how we handle color and coverage separately.
 
     // Set these defaults and then possibly change our mind if there is coverage.
     header->fDiscardIfZeroCoverage = false;
     header->fCoverageOutput = kModulate_CoverageOutput;
 
     // If we do have coverage determine whether it matters.
     bool separateCoverageFromColor = false;
     if (!drawState.isCoverageDrawing() && !skipCoverage &&
         (drawState.numCoverageStages() > 0 || requiresCoverageAttrib)) {
-        // color filter is applied between color/coverage computation
-        if (SkXfermode::kDst_Mode != header->fColorFilterXfermode) {
-            separateCoverageFromColor = true;
-        }
 
         // If we're stenciling then we want to discard samples that have zero coverage
         if (drawState.getStencil().doesWrite()) {
             header->fDiscardIfZeroCoverage = true;
             separateCoverageFromColor = true;
         }
 
         if (gpu->caps()->dualSourceBlendingSupport() &&
             !(blendOpts & (GrDrawState::kEmitCoverage_BlendOptFlag |
                            GrDrawState::kCoverageAsAlpha_BlendOptFlag))) {
@@ skipping 11 matching lines @@
                 separateCoverageFromColor = true;
             }
         } else if (readsDst &&
                    kOne_GrBlendCoeff == srcCoeff &&
                    kZero_GrBlendCoeff == dstCoeff) {
             header->fCoverageOutput = kCombineWithDst_CoverageOutput;
             separateCoverageFromColor = true;
         }
     }
     if (!skipColor) {
-        for (int s = 0; s < drawState.numColorStages(); ++s) {
+        for (int s = firstEffectiveColorStage; s < drawState.numColorStages(); ++s) {
             colorStages->push_back(&drawState.getColorStage(s));
         }
-        header->fColorEffectCnt = drawState.numColorStages();
     }
     if (!skipCoverage) {
         SkTArray<const GrEffectStage*, true>* array;
         if (separateCoverageFromColor) {
             array = coverageStages;
-            header->fCoverageEffectCnt = drawState.numCoverageStages();
         } else {
             array = colorStages;
-            header->fColorEffectCnt += drawState.numCoverageStages();
         }
-        for (int s = 0; s < drawState.numCoverageStages(); ++s) {
+        for (int s = firstEffectiveCoverageStage; s < drawState.numCoverageStages(); ++s) {
             array->push_back(&drawState.getCoverageStage(s));
         }
     }
+    header->fColorEffectCnt = colorStages->count();
+    header->fCoverageEffectCnt = coverageStages->count();
 
     *desc->checksum() = 0;
     *desc->checksum() = SkChecksum::Compute(reinterpret_cast<uint32_t*>(desc->fKey.get()),
                                             newKeyLength);
     desc->fInitialized = true;
 }
 
 GrGLProgramDesc& GrGLProgramDesc::operator= (const GrGLProgramDesc& other) {
     fInitialized = other.fInitialized;
     if (fInitialized) {
         size_t keyLength = other.keyLength();
         fKey.reset(keyLength);
         memcpy(fKey.get(), other.fKey.get(), keyLength);
     }
     return *this;
 }