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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 "SkImagePriv.h"
     13 #include "SkSurface.h"
     14 #include "SkSurfacePriv.h"
     15 
     16 class SkSurface_Base : public SkSurface {
     17 public:
     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 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 SkImage* onNewImageSnapshot(SkBudgeted, ForceCopyMode) = 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      */
     81     virtual void onPrepareForExternalIO() {}
     82 
     83     inline SkCanvas* getCachedCanvas();
     84     inline SkImage* refCachedImage(SkBudgeted, ForceUnique);
     85 
     86     bool hasCachedImage() const { return fCachedImage != nullptr; }
     87 
     88     // called by SkSurface to compute a new genID
     89     uint32_t newGenerationID();
     90 
     91 private:
     92     SkCanvas*   fCachedCanvas;
     93     SkImage*    fCachedImage;
     94 
     95     void aboutToDraw(ContentChangeMode mode);
     96 
     97     // Returns true if there is an outstanding image-snapshot, indicating that a call to aboutToDraw
     98     // would trigger a copy-on-write.
     99     bool outstandingImageSnapshot() const;
    100 
    101     friend class SkCanvas;
    102     friend class SkSurface;
    103 
    104     typedef SkSurface INHERITED;
    105 };
    106 
    107 SkCanvas* SkSurface_Base::getCachedCanvas() {
    108     if (nullptr == fCachedCanvas) {
    109         fCachedCanvas = this->onNewCanvas();
    110         if (fCachedCanvas) {
    111             fCachedCanvas->setSurfaceBase(this);
    112         }
    113     }
    114     return fCachedCanvas;
    115 }
    116 
    117 SkImage* SkSurface_Base::refCachedImage(SkBudgeted budgeted, ForceUnique unique) {
    118     SkImage* snap = fCachedImage;
    119     if (kYes_ForceUnique == unique && snap && !snap->unique()) {
    120         snap = nullptr;
    121     }
    122     if (snap) {
    123         return SkRef(snap);
    124     }
    125     ForceCopyMode fcm = (kYes_ForceUnique == unique) ? kYes_ForceCopyMode :
    126                                                        kNo_ForceCopyMode;
    127     snap = this->onNewImageSnapshot(budgeted, fcm);
    128     if (kNo_ForceUnique == unique) {
    129         SkASSERT(!fCachedImage);
    130         fCachedImage = SkSafeRef(snap);
    131     }
    132     SkASSERT(!fCachedCanvas || fCachedCanvas->getSurfaceBase() == this);
    133     return snap;
    134 }
    135 
    136 #endif
    137