1/*
2 * Copyright 2012 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 SkSurface_Base_DEFINED
9#define SkSurface_Base_DEFINED
10
11#include "SkCanvas.h"
12#include "SkImagePriv.h"
13#include "SkSurface.h"
14#include "SkSurfacePriv.h"
15
16class SkSurface_Base : public SkSurface {
17public:
18    SkSurface_Base(int width, int height, const SkSurfaceProps*);
19    SkSurface_Base(const SkImageInfo&, const SkSurfaceProps*);
20    virtual ~SkSurface_Base();
21
22    virtual GrBackendObject onGetTextureHandle(BackendHandleAccess) {
23        return 0;
24    }
25
26    virtual bool onGetRenderTargetHandle(GrBackendObject*, BackendHandleAccess) {
27        return false;
28    }
29
30    /**
31     *  Allocate a canvas that will draw into this surface. We will cache this
32     *  canvas, to return the same object to the caller multiple times. We
33     *  take ownership, and will call unref() on the canvas when we go out of
34     *  scope.
35     */
36    virtual SkCanvas* onNewCanvas() = 0;
37
38    virtual sk_sp<SkSurface> onNewSurface(const SkImageInfo&) = 0;
39
40    /**
41     *  Allocate an SkImage that represents the current contents of the surface.
42     *  This needs to be able to outlive the surface itself (if need be), and
43     *  must faithfully represent the current contents, even if the surface
44     *  is changed after this called (e.g. it is drawn to via its canvas).
45     */
46    virtual sk_sp<SkImage> onNewImageSnapshot() = 0;
47
48    /**
49     *  Default implementation:
50     *
51     *  image = this->newImageSnapshot();
52     *  if (image) {
53     *      image->draw(canvas, ...);
54     *      image->unref();
55     *  }
56     */
57    virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*);
58
59    /**
60     * Called as a performance hint when the Surface is allowed to make it's contents
61     * undefined.
62     */
63    virtual void onDiscard() {}
64
65    /**
66     *  If the surface is about to change, we call this so that our subclass
67     *  can optionally fork their backend (copy-on-write) in case it was
68     *  being shared with the cachedImage.
69     */
70    virtual void onCopyOnWrite(ContentChangeMode) = 0;
71
72    /**
73     *  Signal the surface to remind its backing store that it's mutable again.
74     *  Called only when we _didn't_ copy-on-write; we assume the copies start mutable.
75     */
76    virtual void onRestoreBackingMutability() {}
77
78    /**
79     * Issue any pending surface IO to the current backend 3D API and resolve any surface MSAA.
80     * Inserts the requested number of semaphores for the gpu to signal when work is complete on the
81     * gpu and inits the array of GrBackendSemaphores with the signaled semaphores.
82     */
83    virtual bool onFlush(int numSemaphores, GrBackendSemaphore* signalSemaphores) {
84        return false;
85    }
86
87    /**
88     * Caused the current backend 3D API to wait on the passed in semaphores before executing new
89     * commands on the gpu. Any previously submitting commands will not be blocked by these
90     * semaphores.
91     */
92    virtual bool onWait(int numSemaphores, const GrBackendSemaphore* waitSemaphores) {
93        return false;
94    }
95
96    inline SkCanvas* getCachedCanvas();
97    inline sk_sp<SkImage> refCachedImage();
98
99    bool hasCachedImage() const { return fCachedImage != nullptr; }
100
101    // called by SkSurface to compute a new genID
102    uint32_t newGenerationID();
103
104private:
105    std::unique_ptr<SkCanvas>   fCachedCanvas;
106    sk_sp<SkImage>              fCachedImage;
107
108    void aboutToDraw(ContentChangeMode mode);
109
110    // Returns true if there is an outstanding image-snapshot, indicating that a call to aboutToDraw
111    // would trigger a copy-on-write.
112    bool outstandingImageSnapshot() const;
113
114    friend class SkCanvas;
115    friend class SkSurface;
116
117    typedef SkSurface INHERITED;
118};
119
120SkCanvas* SkSurface_Base::getCachedCanvas() {
121    if (nullptr == fCachedCanvas) {
122        fCachedCanvas = std::unique_ptr<SkCanvas>(this->onNewCanvas());
123        if (fCachedCanvas) {
124            fCachedCanvas->setSurfaceBase(this);
125        }
126    }
127    return fCachedCanvas.get();
128}
129
130sk_sp<SkImage> SkSurface_Base::refCachedImage() {
131    if (fCachedImage) {
132        return fCachedImage;
133    }
134
135    fCachedImage = this->onNewImageSnapshot();
136
137    SkASSERT(!fCachedCanvas || fCachedCanvas->getSurfaceBase() == this);
138    return fCachedImage;
139}
140
141#endif
142