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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(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(NULL != fGL);
     50         return fGL->hasExtension(extensionName);
     51     }
     52 
     53 protected:
     54     /**
     55      * Subclass implements this to make a GL context. The returned GrGLInterface
     56      * should be populated with functions compatible with the context. The
     57      * format and size of backbuffers does not matter since an FBO will be
     58      * created.
     59      */
     60     virtual const GrGLInterface* createGLContext() = 0;
     61 
     62     /**
     63      * Subclass should destroy the underlying GL context.
     64      */
     65     virtual void destroyGLContext() = 0;
     66 
     67 private:
     68     GrGLuint fFBO;
     69     GrGLuint fColorBufferID;
     70     GrGLuint fDepthStencilBufferID;
     71     const GrGLInterface* fGL;
     72 
     73     typedef SkRefCnt INHERITED;
     74 };
     75 
     76 /**
     77  * Helper macros for using the GL context through the GrGLInterface. Example:
     78  * SK_GL(glCtx, GenTextures(1, &texID));
     79  */
     80 #define SK_GL(ctx, X) (ctx).gl()->fFunctions.f ## X;    \
     81                       SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fFunctions.fGetError())
     82 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X;    \
     83                   SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fFunctions.fGetError())
     84 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->fFunctions.f ## X
     85 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X
     86 
     87 #endif
     88