Make the Sk GL context class an abstract base class

include/gpu/gl/SkGLContextHelper.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 SkGLContextHelper_DEFINED
-#define SkGLContextHelper_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 SkGLContextHelper : public SkRefCnt {
-public:
-    SK_DECLARE_INST_COUNT(SkGLContextHelper)
-
-    SkGLContextHelper();
-    virtual ~SkGLContextHelper();
-
-    /**
-     * Initializes the context and makes it current.
-     */
-    bool init(GrGLStandard forcedGpuAPI, const int width, const int height);
-
-    int getFBOID() const { return fFBO; }
-
-    const GrGLInterface* gl() const { return fGL; }
-
-    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;
-
-    /**
-     * Subclass should destroy the underlying GL context.
-     */
-    virtual void destroyGLContext() = 0;
-
-private:
-    GrGLuint fFBO;
-    GrGLuint fColorBufferID;
-    GrGLuint fDepthStencilBufferID;
-    const GrGLInterface* fGL;
-
-    typedef SkRefCnt INHERITED;
-};
-
-/**
- * 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