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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     /**
     38      * The primary purpose of this function it to provide a means of scheduling
     39      * work on the GPU (since all of the subclasses create primary buffers for
     40      * testing that are small and not meant to be rendered to the screen).
     41      *
     42      * If the drawing surface provided by the platform is double buffered this
     43      * call will cause the platform to swap which buffer is currently being
     44      * targeted.  If the current surface does not include a back buffer, this
     45      * call has no effect.
     46      */
     47     virtual void swapBuffers() const = 0;
     48 
     49     bool hasExtension(const char* extensionName) const {
     50         SkASSERT(NULL != fGL);
     51         return fExtensions.has(extensionName);
     52     }
     53 
     54 protected:
     55     /**
     56      * Subclass implements this to make a GL context. The returned GrGLInterface
     57      * should be populated with functions compatible with the context. The
     58      * format and size of backbuffers does not matter since an FBO will be
     59      * created.
     60      */
     61     virtual const GrGLInterface* createGLContext() = 0;
     62 
     63     /**
     64      * Subclass should destroy the underlying GL context.
     65      */
     66     virtual void destroyGLContext() = 0;
     67 
     68 private:
     69     GrGLExtensions fExtensions;
     70     GrGLuint fFBO;
     71     GrGLuint fColorBufferID;
     72     GrGLuint fDepthStencilBufferID;
     73     const GrGLInterface* fGL;
     74 
     75     typedef SkRefCnt INHERITED;
     76 };
     77 
     78 /**
     79  * Helper macros for using the GL context through the GrGLInterface. Example:
     80  * SK_GL(glCtx, GenTextures(1, &texID));
     81  */
     82 #define SK_GL(ctx, X) (ctx).gl()->f ## X;    \
     83                       SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fGetError())
     84 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->f ## X;    \
     85                   SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fGetError())
     86 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->f ## X
     87 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->f ## X
     88 
     89 #endif
     90