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

This update allows fragment processors to require a field of vectors to the nearest edge. This requirement propagates:

- from child FPs to their parent
- from parent FPs to the GrPaint
- from GrPaint through the PipelineBuilder into GrPipeline
- acessed from GrPipeline by GrGLSLProgramBuilder

GrGLSL generates a variable for the distance vector and passes it down to the GeometryProcessor->emitCode() method.

This CL's base is the CL for adding the BevelNormalSource API: https://codereview.chromium.org/2080993002

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2114993002

Review-Url: https://codereview.chromium.org/2114993002

5 files changed, 79 insertions, 14 deletions

diff --git a/src/core/SkNormalBevelSource.cpp b/src/core/SkNormalBevelSource.cpp
index feccb0cce8..a63e434c3f 100644
--- a/src/core/SkNormalBevelSource.cpp
+++ b/src/core/SkNormalBevelSource.cpp
@@ -8,6 +8,7 @@
 #include "SkNormalBevelSource.h"
 
 #include "SkNormalSource.h"
+#include "SkNormalSourcePriv.h"
 #include "SkPoint3.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
@@ -25,17 +26,19 @@ public:
         , fWidth(width)
         , fHeight(height) {
         this->initClassID<NormalBevelFP>();
+
+        fUsesDistanceVectorField = true;
     }
 
-    class GLSLNormalBevelFP : public GrGLSLFragmentProcessor {
+    class GLSLNormalBevelFP : public GLSLNormalFP {
     public:
         GLSLNormalBevelFP() {
             fPrevWidth = SkFloatToScalar(0.0f);
             fPrevHeight = SkFloatToScalar(0.0f);
         }
 
-        void emitCode(EmitArgs& args) override {
-            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+        void onEmitCode(EmitArgs& args) override {
+            GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
             GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
 
             const char* widthUniName = nullptr;
@@ -46,7 +49,7 @@ public:
             fHeightUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kFloat_GrSLType,
                     kDefault_GrSLPrecision, "Height", &heightUniName);
 
-            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
+            fragBuilder->codeAppendf("%s = vec4(0.0, 0.0, 1.0, 0.0);", args.fOutputColor);
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
@@ -56,7 +59,8 @@ public:
         }
 
     protected:
-        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
+        void setNormalData(const GrGLSLProgramDataManager& pdman,
+                           const GrProcessor& proc) override {
             const NormalBevelFP& normalBevelFP = proc.cast<NormalBevelFP>();
 
             if (fPrevWidth  != normalBevelFP.fWidth) {
diff --git a/src/core/SkNormalFlatSource.cpp b/src/core/SkNormalFlatSource.cpp
index fcb1a4f3ad..bdd65b03e9 100644
--- a/src/core/SkNormalFlatSource.cpp
+++ b/src/core/SkNormalFlatSource.cpp
@@ -8,6 +8,7 @@
 #include "SkNormalFlatSource.h"
 
 #include "SkNormalSource.h"
+#include "SkNormalSourcePriv.h"
 #include "SkPoint3.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
@@ -23,12 +24,12 @@ public:
         this->initClassID<NormalFlatFP>();
     }
 
-    class GLSLNormalFlatFP : public GrGLSLFragmentProcessor {
+    class GLSLNormalFlatFP : public GLSLNormalFP {
     public:
         GLSLNormalFlatFP() {}
 
-        void emitCode(EmitArgs& args) override {
-            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+        void onEmitCode(EmitArgs& args) override {
+            GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
 
             fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
         }
@@ -39,7 +40,8 @@ public:
         }
 
     protected:
-        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {}
+        void setNormalData(const GrGLSLProgramDataManager& pdman,
+                           const GrProcessor& proc) override {}
     };
 
     void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
diff --git a/src/core/SkNormalMapSource.cpp b/src/core/SkNormalMapSource.cpp
index 2ecf1d310d..c2cda099ab 100644
--- a/src/core/SkNormalMapSource.cpp
+++ b/src/core/SkNormalMapSource.cpp
@@ -10,6 +10,7 @@
 #include "SkLightingShader.h"
 #include "SkMatrix.h"
 #include "SkNormalSource.h"
+#include "SkNormalSourcePriv.h"
 #include "SkPM4f.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
@@ -31,13 +32,13 @@ public:
         this->initClassID<NormalMapFP>();
     }
 
-    class GLSLNormalMapFP : public GrGLSLFragmentProcessor {
+    class GLSLNormalMapFP : public GLSLNormalFP {
     public:
         GLSLNormalMapFP()
             : fColumnMajorInvCTM22{0.0f} {}
 
-        void emitCode(EmitArgs& args) override {
-            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+        void onEmitCode(EmitArgs& args) override {
+            GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
             GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
 
             // add uniform
@@ -78,7 +79,8 @@ public:
         }
 
     protected:
-        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
+        void setNormalData(const GrGLSLProgramDataManager& pdman,
+                           const GrProcessor& proc) override {
             const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
 
             const SkMatrix& invCTM = normalMapFP.invCTM();
diff --git a/src/core/SkNormalSource.h b/src/core/SkNormalSource.h
index 8cbb3e4fae..4b09d0b411 100644
--- a/src/core/SkNormalSource.h
+++ b/src/core/SkNormalSource.h
@@ -111,7 +111,7 @@ public:
     /** Returns a normal source that generates a bevel for the given shape. UNIMPLEMENTED: Will
         return straight-up normals only.
 
-        @param  type   the type of bevel to add
+        @param  type   the type of bevel to add.
         @param  width  the width of the bevel, in source space. Must be positive.
         @param  height the height of the plateau, in source space. Can be positive, negative,
                        or zero. A negative height means the simulated bevels slope downwards.
diff --git a/src/core/SkNormalSourcePriv.h b/src/core/SkNormalSourcePriv.h
new file mode 100644
index 0000000000..ce8baf61e4
--- /dev/null
+++ b/src/core/SkNormalSourcePriv.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkNormalSourcePriv_DEFINED
+#define SkNormalSourcePriv_DEFINED
+
+#if SK_SUPPORT_GPU
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+
+/* GLSLFragmentProcessors for NormalSourceImpls must sub-class this class and override onEmitCode,
+ * and setNormalData calls, as well as all other calls FPs normally override, except for the 2
+ * defined in this superclass.
+ * 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. onSetData calls need to be intercepted too because
+ * uniform handlers will be invalid in subclasses where onEmitCode isn't called.
+ * 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.
+ */
+class GLSLNormalFP : public GrGLSLFragmentProcessor {
+public:
+    GLSLNormalFP()
+        : fDidIntercept(false) {}
+
+    void emitCode(EmitArgs& args) final override {
+        if (args.fFp.usesDistanceVectorField() && !args.fGpImplementsDistanceVector) {
+            GrGLSLFPFragmentBuilder* 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);
+
+            fDidIntercept = true;
+        } else {
+            this->onEmitCode(args);
+        }
+    }
+
+    void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) final override {
+        if (!fDidIntercept) {
+            this->setNormalData(pdman, proc);
+        }
+    }
+
+protected:
+    virtual void onEmitCode(EmitArgs& args) = 0;
+    virtual void setNormalData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) = 0;
+
+private:
+    bool fDidIntercept;
+};
+#endif
+
+#endif