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      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 "SkSurface.h"
     13 #include "SkSurfacePriv.h"
     14 
     15 class SkSurface_Base : public SkSurface {
     16 public:
     17     SkSurface_Base(int width, int height, const SkSurfaceProps*);
     18     SkSurface_Base(const SkImageInfo&, const SkSurfaceProps*);
     19     virtual ~SkSurface_Base();
     20 
     21     /**
     22      *  Allocate a canvas that will draw into this surface. We will cache this
     23      *  canvas, to return the same object to the caller multiple times. We
     24      *  take ownership, and will call unref() on the canvas when we go out of
     25      *  scope.
     26      */
     27     virtual SkCanvas* onNewCanvas() = 0;
     28 
     29     virtual SkSurface* onNewSurface(const SkImageInfo&) = 0;
     30 
     31     /**
     32      *  Allocate an SkImage that represents the current contents of the surface.
     33      *  This needs to be able to outlive the surface itself (if need be), and
     34      *  must faithfully represent the current contents, even if the surface
     35      *  is chaged after this calle (e.g. it is drawn to via its canvas).
     36      */
     37     virtual SkImage* onNewImageSnapshot() = 0;
     38 
     39     /**
     40      *  Default implementation:
     41      *
     42      *  image = this->newImageSnapshot();
     43      *  if (image) {
     44      *      image->draw(canvas, ...);
     45      *      image->unref();
     46      *  }
     47      */
     48     virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*);
     49 
     50     /**
     51      * Called as a performance hint when the Surface is allowed to make it's contents
     52      * undefined.
     53      */
     54     virtual void onDiscard() {}
     55 
     56     /**
     57      *  If the surface is about to change, we call this so that our subclass
     58      *  can optionally fork their backend (copy-on-write) in case it was
     59      *  being shared with the cachedImage.
     60      */
     61     virtual void onCopyOnWrite(ContentChangeMode) = 0;
     62 
     63     inline SkCanvas* getCachedCanvas();
     64     inline SkImage* getCachedImage();
     65 
     66     // called by SkSurface to compute a new genID
     67     uint32_t newGenerationID();
     68 
     69 private:
     70     SkCanvas*   fCachedCanvas;
     71     SkImage*    fCachedImage;
     72 
     73     void aboutToDraw(ContentChangeMode mode);
     74     friend class SkCanvas;
     75     friend class SkSurface;
     76 
     77     typedef SkSurface INHERITED;
     78 };
     79 
     80 SkCanvas* SkSurface_Base::getCachedCanvas() {
     81     if (NULL == fCachedCanvas) {
     82         fCachedCanvas = this->onNewCanvas();
     83         if (fCachedCanvas) {
     84             fCachedCanvas->setSurfaceBase(this);
     85         }
     86     }
     87     return fCachedCanvas;
     88 }
     89 
     90 SkImage* SkSurface_Base::getCachedImage() {
     91     if (NULL == fCachedImage) {
     92         fCachedImage = this->onNewImageSnapshot();
     93         SkASSERT(!fCachedCanvas || fCachedCanvas->getSurfaceBase() == this);
     94     }
     95     return fCachedImage;
     96 }
     97 
     98 #endif
     99