Added distance vector support for CircleGeometryProcessor

src/gpu/GrOvalRenderer.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 "GrOvalRenderer.h"
 
 #include "GrBatchFlushState.h"
@@ skipping 65 matching lines @@
     CircleGeometryProcessor(bool stroke, const SkMatrix& localMatrix) : fLocalMatrix(localMatrix){
         this->initClassID<CircleGeometryProcessor>();
         fInPosition = &this->addVertexAttrib(Attribute("inPosition", kVec2f_GrVertexAttribType,
                                                        kHigh_GrSLPrecision));
         fInColor = &this->addVertexAttrib(Attribute("inColor", kVec4ub_GrVertexAttribType));
         fInCircleEdge = &this->addVertexAttrib(Attribute("inCircleEdge",
                                                          kVec4f_GrVertexAttribType));
         fStroke = stroke;
     }
 
+    bool implementsDistanceVector() const override { return true; };
+
     const Attribute* inPosition() const { return fInPosition; }
     const Attribute* inColor() const { return fInColor; }
     const Attribute* inCircleEdge() const { return fInCircleEdge; }
     const SkMatrix& localMatrix() const { return fLocalMatrix; }
+
     virtual ~CircleGeometryProcessor() {}
 
     const char* name() const override { return "CircleEdge"; }
 
     class GLSLProcessor : public GrGLSLGeometryProcessor {
     public:
         GLSLProcessor() {}
 
         void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override{
             const CircleGeometryProcessor& cgp = args.fGP.cast<CircleGeometryProcessor>();
@@ skipping 27 matching lines @@
 
             fragBuilder->codeAppendf("float d = length(%s.xy);", v.fsIn());
             fragBuilder->codeAppendf("float edgeAlpha = clamp(%s.z * (1.0 - d), 0.0, 1.0);",
                                      v.fsIn());
             if (cgp.fStroke) {
                 fragBuilder->codeAppendf("float innerAlpha = clamp(%s.z * (d - %s.w), 0.0, 1.0);",
                                          v.fsIn(), v.fsIn());
                 fragBuilder->codeAppend("edgeAlpha *= innerAlpha;");
             }
 
+            if (args.fDistanceVectorName) {
+                fragBuilder->codeAppendf("%s = %s.z * (normalize(%s.xy) - %s.xy);",

[egdaniel, 2016/07/28 17:30:53]

I feel like this would read easier as something like devVec = normalize(in.xy) *
(in.z - d); where d is from above. Aka scale the vector by how far away we are.
I believe though both equations are the same.

[dvonbeck, 2016/07/28 17:55:14]

That wouldn't work because d is a number from 0-1, not from 0-radius. I could do
devVec = normalize(in.xy) * in.z * (1 - d). That looks easier to read, right?

[egdaniel, 2016/07/28 18:01:52]

Ahh yes duh.

Since we do in.z * (1-d) above, lets store that result in a variable earlier and
reuse it here.

[dvonbeck, 2016/07/29 15:08:55]

Done.

+                                         args.fDistanceVectorName, v.vsOut(), v.vsOut(), v.vsOut());

[egdaniel, 2016/07/28 17:30:53]

why not us fsIn() like the coverage code above?

[dvonbeck, 2016/07/29 15:08:55]

Done.

+            }
+
             fragBuilder->codeAppendf("%s = vec4(edgeAlpha);", args.fOutputCoverage);
         }
 
         static void GenKey(const GrGeometryProcessor& gp,
                            const GrGLSLCaps&,
                            GrProcessorKeyBuilder* b) {
             const CircleGeometryProcessor& cgp = gp.cast<CircleGeometryProcessor>();
             uint16_t key = cgp.fStroke ? 0x1 : 0x0;
             key |= cgp.localMatrix().hasPerspective() ? 0x2 : 0x0;
             b->add32(key);
@@ skipping 1546 matching lines @@
 }
 
 DRAW_BATCH_TEST_DEFINE(RRectBatch) {
     SkMatrix viewMatrix = GrTest::TestMatrixRectStaysRect(random);
     GrColor color = GrRandomColor(random);
     const SkRRect& rrect = GrTest::TestRRectSimple(random);
     return create_rrect_batch(color, viewMatrix, rrect, GrTest::TestStrokeRec(random));
 }
 
 #endif