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      1 
      2 /*
      3  * Copyright 2013 Google Inc.
      4  *
      5  * Use of this source code is governed by a BSD-style license that can be
      6  * found in the LICENSE file.
      7  */
      8 #ifndef SkGLContextHelper_DEFINED
      9 #define SkGLContextHelper_DEFINED
     10 
     11 #include "GrGLInterface.h"
     12 
     13 /**
     14  * Create an offscreen opengl context with an RGBA8 / 8bit stencil FBO.
     15  * Provides a GrGLInterface struct of function pointers for the context.
     16  */
     17 
     18 class SK_API SkGLContextHelper : public SkRefCnt {
     19 public:
     20     SK_DECLARE_INST_COUNT(SkGLContextHelper)
     21 
     22     SkGLContextHelper();
     23     virtual ~SkGLContextHelper();
     24 
     25     /**
     26      * Initializes the context and makes it current.
     27      */
     28     bool init(GrGLStandard forcedGpuAPI, const int width, const int height);
     29 
     30     int getFBOID() const { return fFBO; }
     31 
     32     const GrGLInterface* gl() const { return fGL; }
     33 
     34     virtual void makeCurrent() const = 0;
     35 
     36     /**
     37      * The primary purpose of this function it to provide a means of scheduling
     38      * work on the GPU (since all of the subclasses create primary buffers for
     39      * testing that are small and not meant to be rendered to the screen).
     40      *
     41      * If the drawing surface provided by the platform is double buffered this
     42      * call will cause the platform to swap which buffer is currently being
     43      * targeted.  If the current surface does not include a back buffer, this
     44      * call has no effect.
     45      */
     46     virtual void swapBuffers() const = 0;
     47 
     48     bool hasExtension(const char* extensionName) const {
     49         SkASSERT(fGL);
     50         return fGL->hasExtension(extensionName);
     51     }
     52 
     53     /**
     54      * This notifies the context that we are deliberately testing abandoning
     55      * the context. It is useful for debugging contexts that would otherwise
     56      * test that GPU resources are properly deleted. It also allows a debugging
     57      * context to test that further GL calls are not made by Skia GPU code.
     58      */
     59     void testAbandon();
     60 
     61 protected:
     62     /**
     63      * Subclass implements this to make a GL context. The returned GrGLInterface
     64      * should be populated with functions compatible with the context. The
     65      * format and size of backbuffers does not matter since an FBO will be
     66      * created.
     67      */
     68     virtual const GrGLInterface* createGLContext(GrGLStandard forcedGpuAPI) = 0;
     69 
     70     /**
     71      * Subclass should destroy the underlying GL context.
     72      */
     73     virtual void destroyGLContext() = 0;
     74 
     75 private:
     76     GrGLuint fFBO;
     77     GrGLuint fColorBufferID;
     78     GrGLuint fDepthStencilBufferID;
     79     const GrGLInterface* fGL;
     80 
     81     typedef SkRefCnt INHERITED;
     82 };
     83 
     84 /**
     85  * Helper macros for using the GL context through the GrGLInterface. Example:
     86  * SK_GL(glCtx, GenTextures(1, &texID));
     87  */
     88 #define SK_GL(ctx, X) (ctx).gl()->fFunctions.f ## X;    \
     89                       SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
     90 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X;    \
     91                   SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
     92 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->fFunctions.f ## X
     93 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X
     94 
     95 #endif
     96