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/*
* Copyright 2014 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkCanvasDrawable_DEFINED
#define SkCanvasDrawable_DEFINED
#include "SkRefCnt.h"
class SkCanvas;
class SkPicture;
struct SkRect;
/**
* Base-class for objects that draw into SkCanvas.
*
* The object has a generation ID, which is guaranteed to be unique across all drawables. To
* allow for clients of the drawable that may want to cache the results, the drawable must
* change its generation ID whenever its internal state changes such that it will draw differently.
*/
class SkCanvasDrawable : public SkRefCnt {
public:
SkCanvasDrawable();
/**
* Draws into the specified content. The drawing sequence will be balanced upon return
* (i.e. the saveLevel() on the canvas will match what it was when draw() was called,
* and the current matrix and clip settings will not be changed.
*/
void draw(SkCanvas*);
SkPicture* newPictureSnapshot();
/**
* Return a unique value for this instance. If two calls to this return the same value,
* it is presumed that calling the draw() method will render the same thing as well.
*
* Subclasses that change their state should call notifyDrawingChanged() to ensure that
* a new value will be returned the next time it is called.
*/
uint32_t getGenerationID();
/**
* Return the (conservative) bounds of what the drawable will draw. If the drawable can
* change what it draws (e.g. animation or in response to some external change), then this
* must return a bounds that is always valid for all possible states.
*/
SkRect getBounds();
/**
* Calling this invalidates the previous generation ID, and causes a new one to be computed
* the next time getGenerationID() is called. Typically this is called by the object itself,
* in response to its internal state changing.
*/
void notifyDrawingChanged();
protected:
virtual SkRect onGetBounds() = 0;
virtual void onDraw(SkCanvas*) = 0;
virtual SkPicture* onNewPictureSnapshot();
private:
int32_t fGenerationID;
};
#endif
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