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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 "GrGLExtensions.h"
     12 #include "GrGLInterface.h"
     13 
     14 /**
     15  * Create an offscreen opengl context with an RGBA8 / 8bit stencil FBO.
     16  * Provides a GrGLInterface struct of function pointers for the context.
     17  */
     18 
     19 class SkGLContextHelper : public SkRefCnt {
     20 public:
     21     SK_DECLARE_INST_COUNT(SkGLContextHelper)
     22 
     23     SkGLContextHelper();
     24     virtual ~SkGLContextHelper();
     25 
     26     /**
     27      * Initializes the context and makes it current.
     28      */
     29     bool init(const int width, const int height);
     30 
     31     int getFBOID() const { return fFBO; }
     32 
     33     const GrGLInterface* gl() const { return fGL; }
     34 
     35     virtual void makeCurrent() const = 0;
     36 
     37     bool hasExtension(const char* extensionName) const {
     38         GrAssert(NULL != fGL);
     39         return fExtensions.has(extensionName);
     40     }
     41 
     42 protected:
     43     /**
     44      * Subclass implements this to make a GL context. The returned GrGLInterface
     45      * should be populated with functions compatible with the context. The
     46      * format and size of backbuffers does not matter since an FBO will be
     47      * created.
     48      */
     49     virtual const GrGLInterface* createGLContext() = 0;
     50 
     51     /**
     52      * Subclass should destroy the underlying GL context.
     53      */
     54     virtual void destroyGLContext() = 0;
     55 
     56 private:
     57     GrGLExtensions fExtensions;
     58     GrGLuint fFBO;
     59     GrGLuint fColorBufferID;
     60     GrGLuint fDepthStencilBufferID;
     61     const GrGLInterface* fGL;
     62 
     63     typedef SkRefCnt INHERITED;
     64 };
     65 
     66 /**
     67  * Helper macros for using the GL context through the GrGLInterface. Example:
     68  * SK_GL(glCtx, GenTextures(1, &texID));
     69  */
     70 #define SK_GL(ctx, X) (ctx).gl()->f ## X;    \
     71                       SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fGetError())
     72 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->f ## X;    \
     73                   SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fGetError())
     74 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->f ## X
     75 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->f ## X
     76 
     77 #endif
     78