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) (SkLeftShift(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, int shiftUp); 40 // call this version if you know you don't have a clip 41 inline int setLine(const SkPoint& p0, const SkPoint& p1, int shiftUp); 42 inline int updateLine(SkFixed ax, SkFixed ay, SkFixed bx, SkFixed by); 43 void chopLineWithClip(const SkIRect& clip); 44 45 inline bool intersectsClip(const SkIRect& clip) const { 46 SkASSERT(fFirstY < clip.fBottom); 47 return fLastY >= clip.fTop; 48 } 49 50 #ifdef SK_DEBUG 51 void dump() const { 52 SkDebugf("edge: firstY:%d lastY:%d x:%g dx:%g w:%d\n", fFirstY, fLastY, SkFixedToFloat(fX), SkFixedToFloat(fDX), fWinding); 53 } 54 55 void validate() const { 56 SkASSERT(fPrev && fNext); 57 SkASSERT(fPrev->fNext == this); 58 SkASSERT(fNext->fPrev == this); 59 60 SkASSERT(fFirstY <= fLastY); 61 SkASSERT(SkAbs32(fWinding) == 1); 62 } 63 #endif 64 }; 65 66 struct SkQuadraticEdge : public SkEdge { 67 SkFixed fQx, fQy; 68 SkFixed fQDx, fQDy; 69 SkFixed fQDDx, fQDDy; 70 SkFixed fQLastX, fQLastY; 71 72 int setQuadratic(const SkPoint pts[3], int shiftUp); 73 int updateQuadratic(); 74 }; 75 76 struct SkCubicEdge : public SkEdge { 77 SkFixed fCx, fCy; 78 SkFixed fCDx, fCDy; 79 SkFixed fCDDx, fCDDy; 80 SkFixed fCDDDx, fCDDDy; 81 SkFixed fCLastX, fCLastY; 82 83 int setCubic(const SkPoint pts[4], int shiftUp); 84 int updateCubic(); 85 }; 86 87 int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, int shift) { 88 SkFDot6 x0, y0, x1, y1; 89 90 { 91 #ifdef SK_RASTERIZE_EVEN_ROUNDING 92 x0 = SkScalarRoundToFDot6(p0.fX, shift); 93 y0 = SkScalarRoundToFDot6(p0.fY, shift); 94 x1 = SkScalarRoundToFDot6(p1.fX, shift); 95 y1 = SkScalarRoundToFDot6(p1.fY, shift); 96 #else 97 float scale = float(1 << (shift + 6)); 98 x0 = int(p0.fX * scale); 99 y0 = int(p0.fY * scale); 100 x1 = int(p1.fX * scale); 101 y1 = int(p1.fY * scale); 102 #endif 103 } 104 105 int winding = 1; 106 107 if (y0 > y1) { 108 SkTSwap(x0, x1); 109 SkTSwap(y0, y1); 110 winding = -1; 111 } 112 113 int top = SkFDot6Round(y0); 114 int bot = SkFDot6Round(y1); 115 116 // are we a zero-height line? 117 if (top == bot) { 118 return 0; 119 } 120 121 SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0); 122 const SkFDot6 dy = SkEdge_Compute_DY(top, y0); 123 124 fX = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy)); // + SK_Fixed1/2 125 fDX = slope; 126 fFirstY = top; 127 fLastY = bot - 1; 128 fCurveCount = 0; 129 fWinding = SkToS8(winding); 130 fCurveShift = 0; 131 return 1; 132 } 133 134 135 #endif 136
