GrFP can express distance vector field req., program builder declares variable for it

src/core/SkNormalSource.cpp

Index: src/core/SkNormalSource.cpp
diff --git a/src/core/SkNormalSource.cpp b/src/core/SkNormalSource.cpp
index 394ce8fe45eab79934790050fbeb34f9bf750955..41c3da3995b1a1124409e988ad7935a52045316f 100644
--- a/src/core/SkNormalSource.cpp
+++ b/src/core/SkNormalSource.cpp
@@ -14,9 +14,41 @@
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 
-// Genretating vtable
+#if SK_SUPPORT_GPU
+    #include "GrCoordTransform.h"
+    #include "GrInvariantOutput.h"
+    #include "GrTextureParams.h"
+    #include "glsl/GrGLSLFragmentProcessor.h"
+    #include "glsl/GrGLSLFragmentShaderBuilder.h"
+    #include "SkGr.h"
+#endif
+
+// Generating vtable
 SkNormalSource::~SkNormalSource() {}
 
+#if SK_SUPPORT_GPU
+
+// GLSLFragmentProcessors for NormalSourceImpls must sub-class this class and override onEmitCode.
+// This class exists to intercept emitCode calls and emit <0, 0, 1> if the FP requires a distance
+// vector but the GP doesn't provide it.

[egdaniel, 2016/07/13 19:27:26]

Add to this comment that we don't need to adjust the key here since the use of a
given GP (through its class ID already in the key), will determine what code
gets emitted here.

[dvonbeck, 2016/07/13 21:28:14]

Done.

+class GLSLNormalFP : public GrGLSLFragmentProcessor {
+public:
+    void emitCode(EmitArgs& args) override {
+        if (args.fFp.usesDistanceVectorField() && !args.fGpImplementsDistanceVector) {
+            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+            fragBuilder->codeAppendf("// GLSLNormalFP intercepted emitCode call, GP does not "
+                                     "implement required distance vector feature\n");
+            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
+        } else {
+            this->onEmitCode(args);
+        }
+    }
+protected:
+    virtual void onEmitCode(EmitArgs& args) = 0;
+};
+
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 
 class NormalMapSourceImpl : public SkNormalSource {
@@ -75,13 +107,6 @@ private:
 
 #if SK_SUPPORT_GPU
 
-#include "GrCoordTransform.h"
-#include "GrInvariantOutput.h"
-#include "GrTextureParams.h"
-#include "glsl/GrGLSLFragmentProcessor.h"
-#include "glsl/GrGLSLFragmentShaderBuilder.h"
-#include "SkGr.h"
-
 class NormalMapFP : public GrFragmentProcessor {
 public:
     NormalMapFP(sk_sp<GrFragmentProcessor> mapFP, const SkMatrix& invCTM)
@@ -91,12 +116,12 @@ public:
         this->initClassID<NormalMapFP>();
     }
 
-    class GLSLNormalMapFP : public GrGLSLFragmentProcessor {
+    class GLSLNormalMapFP : public GLSLNormalFP {
     public:
         GLSLNormalMapFP()
             : fColumnMajorInvCTM22{0.0f} {}
 
-        void emitCode(EmitArgs& args) override {
+        void onEmitCode(EmitArgs& args) override {
             GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
             GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
 
@@ -382,13 +407,12 @@ public:
         this->initClassID<NormalFlatFP>();
     }
 
-    class GLSLNormalFlatFP : public GrGLSLFragmentProcessor {
+    class GLSLNormalFlatFP : public GLSLNormalFP {
     public:
         GLSLNormalFlatFP() {}
 
-        void emitCode(EmitArgs& args) override {
+        void onEmitCode(EmitArgs& args) override {
             GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
-
             fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
         }
 
@@ -530,10 +554,12 @@ public:
         : fType(type)
         , fWidth(width)
         , fHeight(height) {
+        fUsesDistanceVectorField = true;
+
         this->initClassID<NormalBevelFP>();
     }
 
-    class GLSLNormalBevelFP : public GrGLSLFragmentProcessor {
+    class GLSLNormalBevelFP : public GLSLNormalFP {
     public:
         GLSLNormalBevelFP() {
             fPrevType = SkNormalSource::BevelType::kLinear;
@@ -541,10 +567,10 @@ public:
             fPrevHeight = SkFloatToScalar(0.0f);
         }
 
-        void emitCode(EmitArgs& args) override {
+        void onEmitCode(EmitArgs& args) override {
             GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
-
-            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
+            fragBuilder->codeAppendf("%s = normalize(vec4(0.0, 0.0, 1.0, 0.0));",
+                                     args.fOutputColor);
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,