1 /* 2 * Copyright 2013 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 SkDeviceLooper_DEFINED 9 #define SkDeviceLooper_DEFINED 10 11 #include "SkBitmap.h" 12 #include "SkMatrix.h" 13 #include "SkRasterClip.h" 14 15 /** 16 * Helper class to manage "tiling" a large coordinate space into managable 17 * chunks, where managable means areas that are <= some max critical coordinate 18 * size. 19 * 20 * The constructor takes an antialiasing bool, which affects what this maximum 21 * allowable size is: If we're drawing BW, then we need coordinates to stay 22 * safely within fixed-point range (we use +- 16K, to give ourselves room to 23 * add/subtract two fixed values and still be in range. If we're drawing AA, 24 * then we reduce that size by the amount that the supersampler scan converter 25 * needs (at the moment, that is 4X, so the "safe" range is +- 4K). 26 * 27 * For performance reasons, the class first checks to see if any help is needed 28 * at all, and if not (i.e. the specified bounds and base bitmap area already 29 * in the safe-zone, then the class does nothing (effectively). 30 */ 31 class SkDeviceLooper { 32 public: 33 SkDeviceLooper(const SkBitmap& base, const SkRasterClip&, 34 const SkIRect& bounds, bool aa); 35 ~SkDeviceLooper(); 36 getBitmap()37 const SkBitmap& getBitmap() const { 38 SkASSERT(kDone_State != fState); 39 SkASSERT(fCurrBitmap); 40 return *fCurrBitmap; 41 } 42 getRC()43 const SkRasterClip& getRC() const { 44 SkASSERT(kDone_State != fState); 45 SkASSERT(fCurrRC); 46 return *fCurrRC; 47 } 48 49 void mapRect(SkRect* dst, const SkRect& src) const; 50 void mapMatrix(SkMatrix* dst, const SkMatrix& src) const; 51 52 /** 53 * Call next to setup the looper to return a valid coordinate chunk. 54 * Each time this returns true, it is safe to call mapRect() and 55 * mapMatrix(), to convert from "global" coordinate values to ones that 56 * are local to this chunk. 57 * 58 * When next() returns false, the list of chunks is done, and mapRect() 59 * and mapMatrix() should no longer be called. 60 */ 61 bool next(); 62 63 private: 64 const SkBitmap& fBaseBitmap; 65 const SkRasterClip& fBaseRC; 66 67 enum State { 68 kDone_State, // iteration is complete, getters will assert 69 kSimple_State, // no translate/clip mods needed 70 kComplex_State 71 }; 72 73 // storage for our tiled versions. Perhaps could use SkTLazy 74 SkBitmap fSubsetBitmap; 75 SkRasterClip fSubsetRC; 76 77 const SkBitmap* fCurrBitmap; 78 const SkRasterClip* fCurrRC; 79 SkIRect fClippedBounds; 80 SkIPoint fCurrOffset; 81 int fDelta; 82 State fState; 83 84 enum Delta { 85 kBW_Delta = 1 << 14, // 16K, gives room to spare for fixedpoint 86 kAA_Delta = kBW_Delta >> 2 // supersample 4x 87 }; 88 fitsInDelta(const SkIRect & r)89 bool fitsInDelta(const SkIRect& r) const { 90 return r.right() < fDelta && r.bottom() < fDelta; 91 } 92 93 bool computeCurrBitmapAndClip(); 94 }; 95 96 #endif 97