Test that GrFragmentProcessors work without input colors.

src/gpu/effects/GrXfermodeFragmentProcessor.cpp

 /*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "effects/GrXfermodeFragmentProcessor.h"
 
 #include "GrFragmentProcessor.h"
@@ skipping 60 matching lines @@
 
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrComposeTwoFragmentProcessor);
 
 const GrFragmentProcessor* GrComposeTwoFragmentProcessor::TestCreate(GrProcessorTestData* d) {
 #if SK_ALLOW_STATIC_GLOBAL_INITIALIZERS
     // Create two random frag procs.
     // For now, we'll prevent either children from being a shader with children to prevent the
     // possibility of an arbitrarily large tree of procs.
     SkAutoTUnref<const GrFragmentProcessor> fpA;
     do {
-        fpA.reset(GrProcessorTestFactory<GrFragmentProcessor>::CreateStage(d));
+        fpA.reset(GrProcessorTestFactory<GrFragmentProcessor>::Create(d));
         SkASSERT(fpA);
     } while (fpA->numChildProcessors() != 0);
     SkAutoTUnref<const GrFragmentProcessor> fpB;
     do {
-        fpB.reset(GrProcessorTestFactory<GrFragmentProcessor>::CreateStage(d));
+        fpB.reset(GrProcessorTestFactory<GrFragmentProcessor>::Create(d));
         SkASSERT(fpB);
     } while (fpB->numChildProcessors() != 0);
 
     SkXfermode::Mode mode = static_cast<SkXfermode::Mode>(
             d->fRandom->nextRangeU(0, SkXfermode::kLastCoeffMode));
     return SkNEW_ARGS(GrComposeTwoFragmentProcessor, (fpA, fpB, mode));
 #else
     SkFAIL("Should not be called if !SK_ALLOW_STATIC_GLOBAL_INITIALIZERS");
     return nullptr;
 #endif
 }
 
 GrGLFragmentProcessor* GrComposeTwoFragmentProcessor::onCreateGLInstance() const{
     return SkNEW_ARGS(GrGLComposeTwoFragmentProcessor, (*this));
 }
 
 /////////////////////////////////////////////////////////////////////
 
 void GrGLComposeTwoFragmentProcessor::emitCode(EmitArgs& args) {
 
     GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
     const GrComposeTwoFragmentProcessor& cs = args.fFp.cast<GrComposeTwoFragmentProcessor>();
 
     // Store alpha of input color and un-premultiply the input color by its alpha. We will
     // re-multiply by this alpha after blending the output colors of the two child procs.
     // This is because we don't want the paint's alpha to affect either child proc's output
     // before the blend; we want to apply the paint's alpha AFTER the blend. This mirrors the
     // software implementation of SkComposeShader.
-    SkString inputAlpha("inputAlpha");
-    fsBuilder->codeAppendf("float %s = %s.a;", inputAlpha.c_str(), args.fInputColor);
-    fsBuilder->codeAppendf("%s /= %s.a;", args.fInputColor, args.fInputColor);
+    const char* opaqueInput = nullptr;
+    const char* inputAlpha = nullptr;
+    if (args.fInputColor) {
+        inputAlpha = "inputAlpha";
+        opaqueInput = "opaqueInput";
+        fsBuilder->codeAppendf("float inputAlpha = %s.a;", args.fInputColor);
+        fsBuilder->codeAppendf("vec4 opaqueInput = vec4(%s.rgb / inputAlpha, 1);",
+                               args.fInputColor);
+    }
 
     // declare outputColor and emit the code for each of the two children
     SkString outputColorSrc(args.fOutputColor);
     outputColorSrc.append("_src");
     fsBuilder->codeAppendf("vec4 %s;\n", outputColorSrc.c_str());
-    this->emitChild(0, args.fInputColor, outputColorSrc.c_str(), args);
+    this->emitChild(0, opaqueInput, outputColorSrc.c_str(), args);
 
     SkString outputColorDst(args.fOutputColor);
     outputColorDst.append("_dst");
     fsBuilder->codeAppendf("vec4 %s;\n", outputColorDst.c_str());
-    this->emitChild(1, args.fInputColor, outputColorDst.c_str(), args);
+    this->emitChild(1, opaqueInput, outputColorDst.c_str(), args);
 
     // emit blend code
     SkXfermode::Mode mode = cs.getMode();
     fsBuilder->codeAppend("{");
     fsBuilder->codeAppendf("// Compose Xfer Mode: %s\n", SkXfermode::ModeName(mode));
     GrGLBlend::AppendPorterDuffBlend(fsBuilder, outputColorSrc.c_str(),
                                      outputColorDst.c_str(), args.fOutputColor, mode);
     fsBuilder->codeAppend("}");
 
     // re-multiply the output color by the input color's alpha
-    fsBuilder->codeAppendf("%s *= %s;", args.fOutputColor, inputAlpha.c_str());
+    if (inputAlpha) {
+        fsBuilder->codeAppendf("%s *= %s;", args.fOutputColor, inputAlpha);
+    }
 }
 
-
 const GrFragmentProcessor* GrXfermodeFragmentProcessor::CreateFromTwoProcessors(
          const GrFragmentProcessor* src, const GrFragmentProcessor* dst, SkXfermode::Mode mode) {
     if (SkXfermode::kLastCoeffMode < mode) {
         return nullptr;
     }
     switch (mode) {
         case SkXfermode::kClear_Mode:
             return GrConstColorProcessor::Create(GrColor_TRANS_BLACK,
                                                  GrConstColorProcessor::kIgnore_InputMode);
             break;
         case SkXfermode::kSrc_Mode:
             return SkRef(src);
             break;
         case SkXfermode::kDst_Mode:
             return SkRef(dst);
             break;
         default:
             return new GrComposeTwoFragmentProcessor(src, dst, mode);
     }
 }