Create GrGLSLVaryingHandler class for program building

src/gpu/glsl/GrGLSLVarying.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrGLSLVarying_DEFINED
+#define GrGLSLVarying_DEFINED
+
+#include "GrAllocator.h"
+#include "GrGeometryProcessor.h"
+#include "GrTypesPriv.h"
+#include "glsl/GrGLSLProgramDataManager.h"
+#include "glsl/GrGLSLShaderVar.h"
+
+class GrGLSLProgramBuilder;
+
+class GrGLSLVarying {
+public:
+    bool vsVarying() const { return kVertToFrag_Varying == fVarying ||
+                                    kVertToGeo_Varying == fVarying; }
+    bool fsVarying() const { return kVertToFrag_Varying == fVarying ||
+                                    kGeoToFrag_Varying == fVarying; }
+    const char* vsOut() const { return fVsOut; }
+    const char* gsIn() const { return fGsIn; }
+    const char* gsOut() const { return fGsOut; }
+    const char* fsIn() const { return fFsIn; }
+    GrSLType type() const { return fType; }
+
+protected:
+    enum Varying {
+        kVertToFrag_Varying,
+        kVertToGeo_Varying,
+        kGeoToFrag_Varying,
+    };
+
+    GrGLSLVarying(GrSLType type, Varying varying)
+        : fVarying(varying), fType(type), fVsOut(nullptr), fGsIn(nullptr), fGsOut(nullptr),
+          fFsIn(nullptr) {}
+
+    Varying fVarying;
+
+private:
+    GrSLType fType;
+    const char* fVsOut;
+    const char* fGsIn;
+    const char* fGsOut;
+    const char* fFsIn;
+
+    friend class GrGLSLVaryingHandler;
+};
+
+struct GrGLSLVertToFrag : public GrGLSLVarying {
+    GrGLSLVertToFrag(GrSLType type)
+        : GrGLSLVarying(type, kVertToFrag_Varying) {}
+};
+
+struct GrGLSLVertToGeo : public GrGLSLVarying {
+    GrGLSLVertToGeo(GrSLType type)
+        : GrGLSLVarying(type, kVertToGeo_Varying) {}
+};
+
+struct GrGLSLGeoToFrag : public GrGLSLVarying {
+    GrGLSLGeoToFrag(GrSLType type)
+        : GrGLSLVarying(type, kGeoToFrag_Varying) {}
+};
+
+static const int kVaryingsPerBlock = 8;
+
+class GrGLSLVaryingHandler {
+public:
+    explicit GrGLSLVaryingHandler(GrGLSLProgramBuilder* program)

[joshualitt, 2015/11/20 17:51:58]

not that it matters, but why is this explicit?

[bsalomon, 2015/11/20 18:20:36]

We strive to make all single arg constructors explicit unless we really really
want the compiler to silently insert conversions.

+        : fVertexInputs(kVaryingsPerBlock)
+        , fVertexOutputs(kVaryingsPerBlock)
+        , fGeomInputs(kVaryingsPerBlock)
+        , fGeomOutputs(kVaryingsPerBlock)
+        , fFragInputs(kVaryingsPerBlock)
+        , fFragOutputs(kVaryingsPerBlock)
+        , fProgramBuilder(program) {}
+
+    virtual ~GrGLSLVaryingHandler() {}
+
+    typedef GrTAllocator<GrGLSLShaderVar> VarArray;
+    typedef GrGLSLProgramDataManager::SeparableVaryingHandle SeparableVaryingHandle;
+
+    /*
+     * addVarying allows fine grained control for setting up varyings between stages. Calling this
+     * functions will make sure all necessary decls are setup for the client. The client however is
+     * responsible for setting up all shader code (e.g "vOut = vIn;") If you just need to take an
+     * attribute and pass it through to an output value in a fragment shader, use
+     * addPassThroughAttribute.
+     * TODO convert most uses of addVarying to addPassThroughAttribute
+     */
+    void addVarying(const char* name,
+                    GrGLSLVarying*,
+                    GrSLPrecision precision = kDefault_GrSLPrecision);
+
+    /*
+     * This call can be used by GP to pass an attribute through all shaders directly to 'output' in
+     * the fragment shader.  Though this call effects both the vertex shader and fragment shader,
+     * it expects 'output' to be defined in the fragment shader before this call is made. If there
+     * is a geometry shader, we will simply take the value of the varying from the first vertex and
+     * that will be set as the output varying for all emitted vertices.
+     * TODO it might be nicer behavior to have a flag to declare output inside this call
+     */
+    void addPassThroughAttribute(const GrGeometryProcessor::Attribute*, const char* output);
+
+    void emitAttributes(const GrGeometryProcessor& gp);
+
+    /*
+     * Creates a fragment shader varying that can be referred to.
+     * Comparable to GrGLSLUniformBuilder::addUniform().
+     */
+    virtual SeparableVaryingHandle addSeparableVarying(
+        const char* name, GrGLSLVertToFrag*,
+        GrSLPrecision fsPrecision = kDefault_GrSLPrecision) = 0;
+
+    void getVertexDecls(SkString* inputDecls, SkString* outputDecls) const;
+    void getGeomDecls(SkString* inputDecls, SkString* outputDecls) const;
+    void getFragDecls(SkString* inputDecls, SkString* outputDecls) const;
+protected:
+    VarArray fVertexInputs;
+    VarArray fVertexOutputs;
+    VarArray fGeomInputs;
+    VarArray fGeomOutputs;
+    VarArray fFragInputs;
+    VarArray fFragOutputs;
+
+    // This is not owned by the class
+    GrGLSLProgramBuilder* fProgramBuilder;
+
+private:
+    void addVertexVarying(const char* name, GrSLPrecision precision, GrGLSLVarying* v);
+    void addGeomVarying(const char* name, GrSLPrecision precision, GrGLSLVarying* v);
+    void addFragVarying(GrSLPrecision precision, GrGLSLVarying* v);
+
+    void addAttribute(const GrShaderVar& var);
+
+    // helper function for get*Decls
+    void appendDecls(const VarArray& vars, SkString* out) const;
+
+    friend class GrGLSLProgramBuilder;
+};
+
+#endif