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

Committed: https://skia.googlesource.com/skia/+/4ef6dfa7089c092c67b0d5ec34e89c1e319af196
Review-Url: https://codereview.chromium.org/2114993002

1 files changed, 57 insertions, 0 deletions

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