1 /* 2 * Copyright 2014 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 SkDrawable_DEFINED 9 #define SkDrawable_DEFINED 10 11 #include "SkRefCnt.h" 12 13 class SkCanvas; 14 class SkPicture; 15 struct SkRect; 16 17 /** 18 * Base-class for objects that draw into SkCanvas. 19 * 20 * The object has a generation ID, which is guaranteed to be unique across all drawables. To 21 * allow for clients of the drawable that may want to cache the results, the drawable must 22 * change its generation ID whenever its internal state changes such that it will draw differently. 23 */ 24 class SkDrawable : public SkRefCnt { 25 public: 26 SkDrawable(); 27 28 /** 29 * Draws into the specified content. The drawing sequence will be balanced upon return 30 * (i.e. the saveLevel() on the canvas will match what it was when draw() was called, 31 * and the current matrix and clip settings will not be changed. 32 */ 33 void draw(SkCanvas*, const SkMatrix* = NULL); 34 void draw(SkCanvas*, SkScalar x, SkScalar y); 35 36 SkPicture* newPictureSnapshot(); 37 38 /** 39 * Return a unique value for this instance. If two calls to this return the same value, 40 * it is presumed that calling the draw() method will render the same thing as well. 41 * 42 * Subclasses that change their state should call notifyDrawingChanged() to ensure that 43 * a new value will be returned the next time it is called. 44 */ 45 uint32_t getGenerationID(); 46 47 /** 48 * Return the (conservative) bounds of what the drawable will draw. If the drawable can 49 * change what it draws (e.g. animation or in response to some external change), then this 50 * must return a bounds that is always valid for all possible states. 51 */ 52 SkRect getBounds(); 53 54 /** 55 * Calling this invalidates the previous generation ID, and causes a new one to be computed 56 * the next time getGenerationID() is called. Typically this is called by the object itself, 57 * in response to its internal state changing. 58 */ 59 void notifyDrawingChanged(); 60 61 protected: 62 virtual SkRect onGetBounds() = 0; 63 virtual void onDraw(SkCanvas*) = 0; 64 65 /** 66 * Default implementation calls onDraw() with a canvas that records into a picture. Subclasses 67 * may override if they have a more efficient way to return a picture for the current state 68 * of their drawable. Note: this picture must draw the same as what would be drawn from 69 * onDraw(). 70 */ 71 virtual SkPicture* onNewPictureSnapshot(); 72 73 private: 74 int32_t fGenerationID; 75 }; 76 77 #endif 78