don't compose with (forced) opaque colors

Bug: skia:
Change-Id: Ic5ea706430b4698e7e937a0cc424ec29b0d8da10
Reviewed-on: https://skia-review.googlesource.com/22029
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 3 insertions, 16 deletions

diff --git a/src/gpu/effects/GrXfermodeFragmentProcessor.cpp b/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
index 94491c976e..ad0427174f 100644
--- a/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
+++ b/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
@@ -146,14 +146,12 @@ private:
     }
 
     GrColor4f constantOutputForConstantInput(GrColor4f input) const override {
-        float alpha = input.fRGBA[3];
-        input = input.opaque();
         GrColor4f srcColor = ConstantOutputForConstantInput(this->childProcessor(0), input);
         GrColor4f dstColor = ConstantOutputForConstantInput(this->childProcessor(1), input);
         SkPM4f src = GrColor4fToSkPM4f(srcColor);
         SkPM4f dst = GrColor4fToSkPM4f(dstColor);
         SkPM4f res = SkBlendMode_Apply(fMode, src, dst);
-        return SkPM4fToGrColor4f(res).mulByScalar(alpha);
+        return SkPM4fToGrColor4f(res);
     }
 
     GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
@@ -205,18 +203,12 @@ void GLComposeTwoFragmentProcessor::emitCode(EmitArgs& args) {
     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
     const ComposeTwoFragmentProcessor& cs = args.fFp.cast<ComposeTwoFragmentProcessor>();
 
-    const char* inputColor = nullptr;
-    if (args.fInputColor) {
-        inputColor = "inputColor";
-        fragBuilder->codeAppendf("vec4 inputColor = vec4(%s.rgb, 1.0);", args.fInputColor);
-    }
-
     // declare outputColor and emit the code for each of the two children
     SkString srcColor("xfer_src");
-    this->emitChild(0, inputColor, &srcColor, args);
+    this->emitChild(0, args.fInputColor, &srcColor, args);
 
     SkString dstColor("xfer_dst");
-    this->emitChild(1, inputColor, &dstColor, args);
+    this->emitChild(1, args.fInputColor, &dstColor, args);
 
     // emit blend code
     SkBlendMode mode = cs.getMode();
@@ -226,11 +218,6 @@ void GLComposeTwoFragmentProcessor::emitCode(EmitArgs& args) {
                             dstColor.c_str(),
                             args.fOutputColor,
                             mode);
-
-    // re-multiply the output color by the input color's alpha
-    if (args.fInputColor) {
-        fragBuilder->codeAppendf("%s *= %s.a;", args.fOutputColor, args.fInputColor);
-    }
 }
 
 sk_sp<GrFragmentProcessor> GrXfermodeFragmentProcessor::MakeFromTwoProcessors(