1/*
2 * Copyright 2011 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef GrRenderTarget_DEFINED
9#define GrRenderTarget_DEFINED
10
11#include "GrSurface.h"
12#include "SkRect.h"
13
14class GrStencilBuffer;
15class GrTexture;
16
17/**
18 * GrRenderTarget represents a 2D buffer of pixels that can be rendered to.
19 * A context's render target is set by setRenderTarget(). Render targets are
20 * created by a createTexture with the kRenderTarget_TextureFlag flag.
21 * Additionally, GrContext provides methods for creating GrRenderTargets
22 * that wrap externally created render targets.
23 */
24class GrRenderTarget : public GrSurface {
25public:
26    SK_DECLARE_INST_COUNT(GrRenderTarget)
27
28    // GrResource overrides
29    virtual size_t gpuMemorySize() const SK_OVERRIDE;
30
31    // GrSurface overrides
32    /**
33     * @return the texture associated with the render target, may be NULL.
34     */
35    virtual GrTexture* asTexture() SK_OVERRIDE { return fTexture; }
36    virtual const GrTexture* asTexture() const SK_OVERRIDE { return fTexture; }
37
38    /**
39     * @return this render target.
40     */
41    virtual GrRenderTarget* asRenderTarget() SK_OVERRIDE { return this; }
42    virtual const GrRenderTarget* asRenderTarget() const  SK_OVERRIDE {
43        return this;
44    }
45
46    virtual bool readPixels(int left, int top, int width, int height,
47                            GrPixelConfig config,
48                            void* buffer,
49                            size_t rowBytes = 0,
50                            uint32_t pixelOpsFlags = 0) SK_OVERRIDE;
51
52    virtual void writePixels(int left, int top, int width, int height,
53                             GrPixelConfig config,
54                             const void* buffer,
55                             size_t rowBytes = 0,
56                             uint32_t pixelOpsFlags = 0) SK_OVERRIDE;
57
58    // GrRenderTarget
59    /**
60     * If this RT is multisampled, this is the multisample buffer
61     * @return the 3D API's handle to this object (e.g. FBO ID in OpenGL)
62     */
63    virtual GrBackendObject getRenderTargetHandle() const = 0;
64
65    /**
66     * If this RT is multisampled, this is the buffer it is resolved to.
67     * Otherwise, same as getRenderTargetHandle().
68     * (In GL a separate FBO ID is used for the MSAA and resolved buffers)
69     * @return the 3D API's handle to this object (e.g. FBO ID in OpenGL)
70     */
71    virtual GrBackendObject getRenderTargetResolvedHandle() const = 0;
72
73    /**
74     * @return true if the surface is multisampled, false otherwise
75     */
76    bool isMultisampled() const { return 0 != fDesc.fSampleCnt; }
77
78    /**
79     * @return the number of samples-per-pixel or zero if non-MSAA.
80     */
81    int numSamples() const { return fDesc.fSampleCnt; }
82
83    /**
84     * Call to indicate the multisample contents were modified such that the
85     * render target needs to be resolved before it can be used as texture. Gr
86     * tracks this for its own drawing and thus this only needs to be called
87     * when the render target has been modified outside of Gr. This has no
88     * effect on wrapped backend render targets.
89     *
90     * @param rect  a rect bounding the area needing resolve. NULL indicates
91     *              the whole RT needs resolving.
92     */
93    void flagAsNeedingResolve(const SkIRect* rect = NULL);
94
95    /**
96     * Call to override the region that needs to be resolved.
97     */
98    void overrideResolveRect(const SkIRect rect);
99
100    /**
101     * Call to indicate that GrRenderTarget was externally resolved. This may
102     * allow Gr to skip a redundant resolve step.
103     */
104    void flagAsResolved() { fResolveRect.setLargestInverted(); }
105
106    /**
107     * @return true if the GrRenderTarget requires MSAA resolving
108     */
109    bool needsResolve() const { return !fResolveRect.isEmpty(); }
110
111    /**
112     * Returns a rect bounding the region needing resolving.
113     */
114    const SkIRect& getResolveRect() const { return fResolveRect; }
115
116    /**
117     * If the render target is multisampled this will perform a multisample
118     * resolve. Any pending draws to the target are first flushed. This only
119     * applies to render targets that are associated with GrTextures. After the
120     * function returns the GrTexture will contain the resolved pixels.
121     */
122    void resolve();
123
124    /**
125     * Provide a performance hint that the render target's contents are allowed
126     * to become undefined.
127     */
128    void discard();
129
130    // a MSAA RT may require explicit resolving , it may auto-resolve (e.g. FBO
131    // 0 in GL), or be unresolvable because the client didn't give us the
132    // resolve destination.
133    enum ResolveType {
134        kCanResolve_ResolveType,
135        kAutoResolves_ResolveType,
136        kCantResolve_ResolveType,
137    };
138    virtual ResolveType getResolveType() const = 0;
139
140    /**
141     * GrStencilBuffer is not part of the public API.
142     */
143    GrStencilBuffer* getStencilBuffer() const { return fStencilBuffer; }
144    void setStencilBuffer(GrStencilBuffer* stencilBuffer);
145
146protected:
147    GrRenderTarget(GrGpu* gpu,
148                   bool isWrapped,
149                   GrTexture* texture,
150                   const GrTextureDesc& desc)
151        : INHERITED(gpu, isWrapped, desc)
152        , fStencilBuffer(NULL)
153        , fTexture(texture) {
154        fResolveRect.setLargestInverted();
155    }
156
157    // override of GrResource
158    virtual void onAbandon() SK_OVERRIDE;
159    virtual void onRelease() SK_OVERRIDE;
160
161private:
162    friend class GrTexture;
163    // called by ~GrTexture to remove the non-ref'ed back ptr.
164    void owningTextureDestroyed() {
165        SkASSERT(NULL != fTexture);
166        fTexture = NULL;
167    }
168
169    GrStencilBuffer*  fStencilBuffer;
170    GrTexture*        fTexture; // not ref'ed
171
172    SkIRect           fResolveRect;
173
174    typedef GrSurface INHERITED;
175};
176
177#endif
178