SkGLContextHelper.h revision c9542ca3d00878a18a57af80037060d6374d5650 
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
19class SkGLContextHelper : public SkRefCnt {
20public:
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
54protected:
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
68private:
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