Add GM/slide to simulate Android-style reveal clip

src/effects/SkGaussianEdgeShader.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGaussianEdgeShader.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
@@ skipping 49 matching lines @@
 
         // enable output of distance information for shape
         fUsesDistanceVectorField = true;
     }
 
     class GLSLGaussianEdgeFP : public GrGLSLFragmentProcessor {
     public:
         GLSLGaussianEdgeFP() {}
 
         void emitCode(EmitArgs& args) override {
-
             GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
 
-            fragBuilder->codeAppendf("vec4 color = %s;", args.fInputColor);
-            fragBuilder->codeAppend("float radius = color.g*64.0;");
-            fragBuilder->codeAppend("float pad = color.b*64.0;");
+            if (!args.fGpImplementsDistanceVector) {
+                fragBuilder->codeAppendf("// GP does not implement fsDistanceVector - "
+                                         " returning black in \n");
+                fragBuilder->codeAppendf("%s = vec4(0, 0, 0, 0);", args.fOutputColor);

[jvanverth1, 2016/09/08 14:15:52]

Maybe (0, 0, 0, color.r) instead? At least you'd get the right shade without the
blurred edge.

[robertphillips, 2016/09/08 14:34:50]

Done.

+            } else {
+                fragBuilder->codeAppendf("vec4 color = %s;", args.fInputColor);
+                fragBuilder->codeAppend("float radius = color.g*64.0;");
+                fragBuilder->codeAppend("float pad = color.b*64.0;");
 
-            fragBuilder->codeAppendf("float factor = 1.0 - clamp((%s.z - pad)/radius, 0.0, 1.0);",
-                                     fragBuilder->distanceVectorName());
-            fragBuilder->codeAppend("factor = exp(-factor * factor * 4.0) - 0.018;");
-            fragBuilder->codeAppendf("%s = factor*vec4(0.0, 0.0, 0.0, color.r);", args.fOutputColor);
+                fragBuilder->codeAppendf("float factor = 1.0 - clamp((%s.z - pad)/radius, 0.0, 1.0);",
+                                         fragBuilder->distanceVectorName());
+                fragBuilder->codeAppend("factor = exp(-factor * factor * 4.0) - 0.018;");
+                fragBuilder->codeAppendf("%s = factor*vec4(0.0, 0.0, 0.0, color.r);",
+                                         args.fOutputColor);
+            }
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
                            GrProcessorKeyBuilder* b) {
             // only one shader generated currently
             b->add32(0x0);
         }
 
     protected:
         void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {}
@@ skipping 35 matching lines @@
 void SkGaussianEdgeShaderImpl::toString(SkString* str) const {
     str->appendf("GaussianEdgeShader: ()");
 }
 #endif
 
 sk_sp<SkFlattenable> SkGaussianEdgeShaderImpl::CreateProc(SkReadBuffer& buf) {
     return sk_make_sp<SkGaussianEdgeShaderImpl>();
 }
 
 void SkGaussianEdgeShaderImpl::flatten(SkWriteBuffer& buf) const {
-    this->INHERITED::flatten(buf);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 sk_sp<SkShader> SkGaussianEdgeShader::Make() {
     return sk_make_sp<SkGaussianEdgeShaderImpl>();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkGaussianEdgeShader)
 SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkGaussianEdgeShaderImpl)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
 
 ///////////////////////////////////////////////////////////////////////////////