Optimizations and more documentation of SkShadowShader

samplecode/SampleShadowing.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 "SampleCode.h"
 #include "SkPictureRecorder.h"
 #include "SkShadowPaintFilterCanvas.h"
@@ skipping 35 matching lines @@
         fSliders[1].fGeometry = SkRect::MakeLTRB(100, 420, 110, 440);
         fSliders[1].fOffset = 0.0f;
         fSliders[1].fScale = 10.0f;
 
         fSliders[2].fGeometry = SkRect::MakeLTRB(0, 440, 10, 460);
         fSliders[2].fOffset = 0.0f;
         fSliders[2].fScale = 0.0025f;
 
         fShadowParams.fShadowRadius = 4.0f;
         fShadowParams.fBiasingConstant = 0.3f;
-        fShadowParams.fMinVariance = 1024;
+        fShadowParams.fMinVariance = 0.015625;

[jvanverth1, 2016/08/29 18:30:14]

It's not clear to me why this is now 1/64.

[vjiaoblack, 2016/08/29 19:45:21]

I'll put the tranform in later.

It was because I use variance in a 0 - 1 space instead of 0 - 65536 space in the
shader now

         fShadowParams.fType = SkShadowParams::kVariance_ShadowType;
     }
 
 protected:
     bool onQuery(SkEvent *evt) override {
         if (SampleCode::TitleQ(*evt)) {
             SampleCode::TitleR(evt, "shadowing");
             return true;
         }
 
@@ skipping 231 matching lines @@
     sk_sp<SkLights> fLights;
 
     typedef SampleView INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 static SkView* MyFactory() { return new ShadowingView; }
 static SkViewRegister reg(MyFactory);
 
 #endif