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
18class SK_API SkGLContextHelper : public SkRefCnt {
19public:
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
53protected:
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
67private:
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