1 2 /* 3 * Copyright 2011 The Android Open Source Project 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef SkDrawLooper_DEFINED 11 #define SkDrawLooper_DEFINED 12 13 #include "SkFlattenable.h" 14 15 class SkCanvas; 16 class SkPaint; 17 struct SkRect; 18 class SkString; 19 20 /** \class SkDrawLooper 21 Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are, 22 and something is drawn to a canvas with that paint, the looper subclass will 23 be called, allowing it to modify the canvas and/or paint for that draw call. 24 More than that, via the next() method, the looper can modify the draw to be 25 invoked multiple times (hence the name loop-er), allow it to perform effects 26 like shadows or frame/fills, that require more than one pass. 27 */ 28 class SK_API SkDrawLooper : public SkFlattenable { 29 public: 30 SK_DECLARE_INST_COUNT(SkDrawLooper) 31 32 /** 33 * Called right before something is being drawn. This will be followed by 34 * calls to next() until next() returns false. 35 */ 36 virtual void init(SkCanvas*) = 0; 37 38 /** 39 * Called in a loop (after init()). Each time true is returned, the object 40 * is drawn (possibly with a modified canvas and/or paint). When false is 41 * finally returned, drawing for the object stops. 42 * 43 * On each call, the paint will be in its original state, but the canvas 44 * will be as it was following the previous call to next() or init(). 45 * 46 * The implementation must ensure that, when next() finally returns false, 47 * that the canvas has been restored to the state it was initially, before 48 * init() was first called. 49 */ 50 virtual bool next(SkCanvas*, SkPaint* paint) = 0; 51 52 /** 53 * The fast bounds functions are used to enable the paint to be culled early 54 * in the drawing pipeline. If a subclass can support this feature it must 55 * return true for the canComputeFastBounds() function. If that function 56 * returns false then computeFastBounds behavior is undefined otherwise it 57 * is expected to have the following behavior. Given the parent paint and 58 * the parent's bounding rect the subclass must fill in and return the 59 * storage rect, where the storage rect is with the union of the src rect 60 * and the looper's bounding rect. 61 */ 62 virtual bool canComputeFastBounds(const SkPaint& paint); 63 virtual void computeFastBounds(const SkPaint& paint, 64 const SkRect& src, SkRect* dst); 65 66 SkDEVCODE(virtual void toString(SkString* str) const = 0;) 67 68 protected: 69 SkDrawLooper() {} 70 SkDrawLooper(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {} 71 72 private: 73 typedef SkFlattenable INHERITED; 74 }; 75 76 #endif 77
