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 SkPixmap& base, const SkRasterClip&, const SkIRect& bounds, bool aa); 34 ~SkDeviceLooper(); 35 getPixmap()36 const SkPixmap& getPixmap() const { 37 SkASSERT(kDone_State != fState); 38 SkASSERT(fCurrDst); 39 return *fCurrDst; 40 } 41 getRC()42 const SkRasterClip& getRC() const { 43 SkASSERT(kDone_State != fState); 44 SkASSERT(fCurrRC); 45 return *fCurrRC; 46 } 47 48 void mapRect(SkRect* dst, const SkRect& src) const; 49 void mapMatrix(SkMatrix* dst, const SkMatrix& src) const; 50 51 /** 52 * Call next to setup the looper to return a valid coordinate chunk. 53 * Each time this returns true, it is safe to call mapRect() and 54 * mapMatrix(), to convert from "global" coordinate values to ones that 55 * are local to this chunk. 56 * 57 * When next() returns false, the list of chunks is done, and mapRect() 58 * and mapMatrix() should no longer be called. 59 */ 60 bool next(); 61 62 private: 63 const SkPixmap& fBaseDst; 64 const SkRasterClip& fBaseRC; 65 66 enum State { 67 kDone_State, // iteration is complete, getters will assert 68 kSimple_State, // no translate/clip mods needed 69 kComplex_State 70 }; 71 72 // storage for our tiled versions. Perhaps could use SkTLazy 73 SkPixmap fSubsetDst; 74 SkRasterClip fSubsetRC; 75 76 const SkPixmap* fCurrDst; 77 const SkRasterClip* fCurrRC; 78 SkIRect fClippedBounds; 79 SkIPoint fCurrOffset; 80 int fDelta; 81 State fState; 82 83 enum Delta { 84 kBW_Delta = 1 << 14, // 16K, gives room to spare for fixedpoint 85 kAA_Delta = kBW_Delta >> 2 // supersample 4x 86 }; 87 fitsInDelta(const SkIRect & r)88 bool fitsInDelta(const SkIRect& r) const { 89 return r.right() < fDelta && r.bottom() < fDelta; 90 } 91 92 bool computeCurrBitmapAndClip(); 93 }; 94 95 #endif 96