1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SkDrawLooper_DEFINED 18 #define SkDrawLooper_DEFINED 19 20 #include "SkFlattenable.h" 21 22 ////////////////// EXPERIMENTAL ////////////////////////// 23 24 class SkCanvas; 25 class SkPaint; 26 27 /** \class SkDrawLooper 28 Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are, 29 and something is drawn to a canvas with that paint, the looper subclass will 30 be called, allowing it to modify the canvas and/or paint for that draw call. 31 More than that, via the next() method, the looper can modify the draw to be 32 invoked multiple times (hence the name loop-er), allow it to perform effects 33 like shadows or frame/fills, that require more than one pass. 34 */ 35 class SkDrawLooper : public SkFlattenable { 36 public: 37 /** Called right before something is being drawn to the specified canvas 38 with the specified paint. Subclass that want to modify either parameter 39 can do so now. 40 */ 41 virtual void init(SkCanvas*, SkPaint*) {} 42 /** Called in a loop (after init()). Each time true is returned, the object 43 is drawn (possibly with a modified canvas and/or paint). When false is 44 finally returned, drawing for the object stops. 45 */ 46 virtual bool next() { return false; } 47 /** Called after the looper has finally returned false from next(), allowing 48 the looper to restore the canvas/paint to their original states. 49 is this required, since the subclass knows when it is done??? 50 should we pass the canvas/paint here, and/or to the next call 51 so that subclasses don't need to retain pointers to them during the 52 loop? 53 */ 54 virtual void restore() {} 55 56 protected: 57 SkDrawLooper() {} 58 SkDrawLooper(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {} 59 60 private: 61 typedef SkFlattenable INHERITED; 62 }; 63 64 #endif 65
