Some refactoring of GrCustomStage and friends

Review URL: http://codereview.appspot.com/6209071/



git-svn-id: http://skia.googlecode.com/svn/trunk@4003 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 129 insertions, 7 deletions

diff --git a/include/gpu/GrCustomStage.h b/include/gpu/GrCustomStage.h
index 64bcce3036..908b10d6ec 100644
--- a/include/gpu/GrCustomStage.h
+++ b/include/gpu/GrCustomStage.h
@@ -9,16 +9,18 @@
 #define GrCustomStage_DEFINED
 
 #include "GrRefCnt.h"
+#include "GrNoncopyable.h"
+#include "GrProgramStageFactory.h"
+#include "SkTemplates.h"
 
 class GrContext;
-class GrProgramStageFactory;
 
 /** Provides custom vertex shader, fragment shader, uniform data for a
-    particular stage of the Ganesh shading pipeline.
-    TODO: may want to refcount these? */
+    particular stage of the Ganesh shading pipeline. */
 class GrCustomStage : public GrRefCnt {
 
 public:
+    typedef GrProgramStageFactory::StageKey StageKey;
 
     GrCustomStage();
     virtual ~GrCustomStage();
@@ -31,10 +33,24 @@ public:
         stage guaranteed to produce an opaque output? */
     virtual bool isOpaque(bool inputTextureIsOpaque) const;
 
-    /** This pointer, besides creating back-end-specific helper
-        objects, is used for run-time-type-identification. Every
-        subclass must return a consistent unique value for it. */
-    virtual GrProgramStageFactory* getFactory() const = 0;
+    /** This object, besides creating back-end-specific helper
+        objects, is used for run-time-type-identification. The factory should be
+        an instance of templated class, GrTProgramStageFactory. It is templated
+        on the subclass of GrCustomStage. The subclass must have a nested type
+        (or typedef) named GLProgramStage which will be the subclass of
+        GrGLProgramStage created by the factory.
+
+        Example:
+        class MyCustomStage : public GrCustomStage {
+        ...
+            virtual const GrProgramStageFactory& getFactory() const 
+                                                            SK_OVERRIDE {
+                return GrTProgramStageFactory<MyCustomStage>::getInstance();
+            }
+        ...
+        };
+     */
+    virtual const GrProgramStageFactory& getFactory() const = 0;
 
     /** Returns true if the other custom stage will generate
         equal output.
diff --git a/include/gpu/GrProgramStageFactory.h b/include/gpu/GrProgramStageFactory.h
new file mode 100644
index 0000000000..e73b9ba7df
--- /dev/null
+++ b/include/gpu/GrProgramStageFactory.h
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrProgramStageFactory_DEFINED
+#define GrProgramStageFactory_DEFINED
+
+#include "GrTypes.h"
+
+/** Given a GrCustomStage of a particular type, creates the corresponding
+    graphics-backend-specific GrProgramStage. Also tracks equivalence
+    of shaders generated via a key.
+ */
+
+class GrCustomStage;
+class GrGLProgramStage;
+
+class GrProgramStageFactory : public GrNoncopyable {
+public:
+    typedef uint16_t StageKey;
+    enum {
+        kProgramStageKeyBits = 10,
+    };
+
+    virtual StageKey stageKey(const GrCustomStage* stage) const = 0;
+    virtual GrGLProgramStage* createGLInstance(
+        const GrCustomStage* stage) const = 0;
+
+    bool operator ==(const GrProgramStageFactory& b) const {
+        return fStageClassID == b.fStageClassID;
+    }
+    bool operator !=(const GrProgramStageFactory& b) const {
+        return !(*this == b);
+    }
+
+protected:
+    enum {
+        kIllegalStageClassID = 0,
+    };
+
+    GrProgramStageFactory() {
+        fStageClassID = kIllegalStageClassID;
+    }
+
+    static StageKey GenID() {
+        // fCurrStageClassID has been initialized to kIllegalStageClassID. The
+        // atomic inc returns the old value not the incremented value. So we add
+        // 1 to the returned value.
+        int32_t id = sk_atomic_inc(&fCurrStageClassID) + 1;
+        GrAssert(id < (1 << (8 * sizeof(StageKey) - kProgramStageKeyBits)));
+        return id;
+    }
+
+    StageKey fStageClassID;
+
+private:
+    static int32_t fCurrStageClassID;
+};
+
+template <typename StageClass>
+class GrTProgramStageFactory : public GrProgramStageFactory {
+
+public:
+    typedef typename StageClass::GLProgramStage GLProgramStage; 
+    
+    /** Returns an value that idenitifes the shader code generated by
+        a GrCustomStage. This enables caching of generated shaders. Part of the
+        id identifies the GrCustomShader subclass. The remainder is based
+        on the aspects of the GrCustomStage object's configuration that affect
+        code generation. */
+    virtual StageKey stageKey(const GrCustomStage* stage) const SK_OVERRIDE {
+        GrAssert(kIllegalStageClassID != fStageClassID);
+        StageKey stageID = GLProgramStage::GenKey(stage);
+        static const StageKey kIllegalIDMask =
+            ~((1 << kProgramStageKeyBits) - 1);
+        GrAssert(!(kIllegalIDMask & stageID));
+        return fStageClassID | stageID;
+    }
+
+    /** Returns a new instance of the appropriate *GL* implementation class
+     for the given GrCustomStage; caller is responsible for deleting
+     the object. */
+    virtual GLProgramStage* createGLInstance(
+                        const GrCustomStage* stage) const SK_OVERRIDE {
+        return new GLProgramStage(stage);
+    }
+
+    static const GrProgramStageFactory& getInstance() {
+        static SkAlignedSTStorage<1, GrTProgramStageFactory> gInstanceMem;
+        static const GrTProgramStageFactory* gInstance;
+        if (!gInstance) {
+            gInstance = new (gInstanceMem.get()) GrTProgramStageFactory();
+        }
+        return *gInstance;
+    }
+
+protected:
+    GrTProgramStageFactory() {
+        fStageClassID = GenID() << kProgramStageKeyBits;
+    }
+};
+
+#endif