1 2 /* 3 * Copyright 2006 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 SkEdge_DEFINED 11 #define SkEdge_DEFINED 12 13 #include "SkRect.h" 14 #include "SkFDot6.h" 15 #include "SkMath.h" 16 17 // This correctly favors the lower-pixel when y0 is on a 1/2 pixel boundary 18 #define SkEdge_Compute_DY(top, y0) ((top << 6) + 32 - (y0)) 19 20 struct SkEdge { 21 enum Type { 22 kLine_Type, 23 kQuad_Type, 24 kCubic_Type 25 }; 26 27 SkEdge* fNext; 28 SkEdge* fPrev; 29 30 SkFixed fX; 31 SkFixed fDX; 32 int32_t fFirstY; 33 int32_t fLastY; 34 int8_t fCurveCount; // only used by kQuad(+) and kCubic(-) 35 uint8_t fCurveShift; // appled to all Dx/DDx/DDDx except for fCubicDShift exception 36 uint8_t fCubicDShift; // applied to fCDx and fCDy only in cubic 37 int8_t fWinding; // 1 or -1 38 39 int setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip, 40 int shiftUp); 41 // call this version if you know you don't have a clip 42 inline int setLine(const SkPoint& p0, const SkPoint& p1, int shiftUp); 43 inline int updateLine(SkFixed ax, SkFixed ay, SkFixed bx, SkFixed by); 44 void chopLineWithClip(const SkIRect& clip); 45 46 inline bool intersectsClip(const SkIRect& clip) const { 47 SkASSERT(fFirstY < clip.fBottom); 48 return fLastY >= clip.fTop; 49 } 50 51 #ifdef SK_DEBUG 52 void dump() const { 53 SkDebugf("edge: firstY:%d lastY:%d x:%g dx:%g w:%d\n", fFirstY, fLastY, SkFixedToFloat(fX), SkFixedToFloat(fDX), fWinding); 54 } 55 56 void validate() const { 57 SkASSERT(fPrev && fNext); 58 SkASSERT(fPrev->fNext == this); 59 SkASSERT(fNext->fPrev == this); 60 61 SkASSERT(fFirstY <= fLastY); 62 SkASSERT(SkAbs32(fWinding) == 1); 63 } 64 #endif 65 }; 66 67 struct SkQuadraticEdge : public SkEdge { 68 SkFixed fQx, fQy; 69 SkFixed fQDx, fQDy; 70 SkFixed fQDDx, fQDDy; 71 SkFixed fQLastX, fQLastY; 72 73 int setQuadratic(const SkPoint pts[3], int shiftUp); 74 int updateQuadratic(); 75 }; 76 77 struct SkCubicEdge : public SkEdge { 78 SkFixed fCx, fCy; 79 SkFixed fCDx, fCDy; 80 SkFixed fCDDx, fCDDy; 81 SkFixed fCDDDx, fCDDDy; 82 SkFixed fCLastX, fCLastY; 83 84 int setCubic(const SkPoint pts[4], const SkIRect* clip, int shiftUp); 85 int updateCubic(); 86 }; 87 88 int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, int shift) { 89 SkFDot6 x0, y0, x1, y1; 90 91 { 92 #ifdef SK_SCALAR_IS_FLOAT 93 float scale = float(1 << (shift + 6)); 94 x0 = int(p0.fX * scale); 95 y0 = int(p0.fY * scale); 96 x1 = int(p1.fX * scale); 97 y1 = int(p1.fY * scale); 98 #else 99 shift = 10 - shift; 100 x0 = p0.fX >> shift; 101 y0 = p0.fY >> shift; 102 x1 = p1.fX >> shift; 103 y1 = p1.fY >> shift; 104 #endif 105 } 106 107 int winding = 1; 108 109 if (y0 > y1) { 110 SkTSwap(x0, x1); 111 SkTSwap(y0, y1); 112 winding = -1; 113 } 114 115 int top = SkFDot6Round(y0); 116 int bot = SkFDot6Round(y1); 117 118 // are we a zero-height line? 119 if (top == bot) { 120 return 0; 121 } 122 123 SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0); 124 const int dy = SkEdge_Compute_DY(top, y0); 125 126 fX = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy)); // + SK_Fixed1/2 127 fDX = slope; 128 fFirstY = top; 129 fLastY = bot - 1; 130 fCurveCount = 0; 131 fWinding = SkToS8(winding); 132 fCurveShift = 0; 133 return 1; 134 } 135 136 137 #endif 138
