Refactor SkGLContext to be actually extendable

include/gpu/gl/SkGLContext.h

 
 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkGLContext_DEFINED
 #define SkGLContext_DEFINED
 
 #include "GrGLInterface.h"
 
 /**
  * Create an offscreen opengl context with an RGBA8 / 8bit stencil FBO.
  * Provides a GrGLInterface struct of function pointers for the context.
  */
 
 class SK_API SkGLContext : public SkRefCnt {
 public:
     SK_DECLARE_INST_COUNT(SkGLContext)
 
-    SkGLContext();
-    virtual ~SkGLContext();
+    virtual ~SkGLContext() SK_OVERRIDE;
 
-    /**
-     * Initializes the context and makes it current.
-     */
-    bool init(GrGLStandard forcedGpuAPI, const int width, const int height);
+    bool isValid() const { return NULL != gl(); }
 
-    int getFBOID() const { return fFBO; }
-
-    const GrGLInterface* gl() const { return fGL; }
+    const GrGLInterface* gl() const { return fGL.get(); }
 
     virtual void makeCurrent() const = 0;
 
     /**
      * The primary purpose of this function it to provide a means of scheduling
      * work on the GPU (since all of the subclasses create primary buffers for
      * testing that are small and not meant to be rendered to the screen).
      *
      * If the drawing surface provided by the platform is double buffered this
      * call will cause the platform to swap which buffer is currently being
      * targeted.  If the current surface does not include a back buffer, this
      * call has no effect.
      */
     virtual void swapBuffers() const = 0;
 
-    bool hasExtension(const char* extensionName) const {
-        SkASSERT(fGL);
-        return fGL->hasExtension(extensionName);
-    }
-
     /**
      * This notifies the context that we are deliberately testing abandoning
      * the context. It is useful for debugging contexts that would otherwise
      * test that GPU resources are properly deleted. It also allows a debugging
      * context to test that further GL calls are not made by Skia GPU code.
      */
     void testAbandon();
 
 protected:
-    /**
-     * Subclass implements this to make a GL context. The returned GrGLInterface
-     * should be populated with functions compatible with the context. The
-     * format and size of backbuffers does not matter since an FBO will be
-     * created.
-     */
-    virtual const GrGLInterface* createGLContext(GrGLStandard forcedGpuAPI) = 0;
+    SkGLContext();
 
-    /**
-     * Subclass should destroy the underlying GL context.
-     */
-    virtual void destroyGLContext() = 0;
-
-private:
-    GrGLuint fFBO;
-    GrGLuint fColorBufferID;
-    GrGLuint fDepthStencilBufferID;
-    const GrGLInterface* fGL;
+    /** Subclass provides the gl interface object if construction was
+     *  successful. */
+    SkAutoTUnref<const GrGLInterface> fGL;
 
     typedef SkRefCnt INHERITED;
 };
 
 /** Creates platform-dependent GL context object
+ * Returns a valid gl context object or NULL if such can not be created.
  * Note: If Skia embedder needs a custom GL context that sets up the GL
  * interface, this function should be implemented by the embedder.
  * Otherwise, the default implementation for the platform should be compiled in
  * the library.
  */
-SK_API SkGLContext* SkCreatePlatformGLContext();
+SK_API SkGLContext* SkCreatePlatformGLContext(GrGLStandard forcedGpuAPI);
 
 /**
  * Helper macros for using the GL context through the GrGLInterface. Example:
  * SK_GL(glCtx, GenTextures(1, &texID));
  */
 #define SK_GL(ctx, X) (ctx).gl()->fFunctions.f ## X;    \
                       SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X;    \
                   SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->fFunctions.f ## X
 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X
 
 #endif