1 /* 2 * Copyright 2006 The Android Open Source Project 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 9 #ifndef SkEdge_DEFINED 10 #define SkEdge_DEFINED 11 12 #include "SkRect.h" 13 #include "SkFDot6.h" 14 #include "SkMath.h" 15 16 // This correctly favors the lower-pixel when y0 is on a 1/2 pixel boundary 17 #define SkEdge_Compute_DY(top, y0) (SkLeftShift(top, 6) + 32 - (y0)) 18 19 struct SkEdge { 20 enum Type { 21 kLine_Type, 22 kQuad_Type, 23 kCubic_Type 24 }; 25 26 SkEdge* fNext; 27 SkEdge* fPrev; 28 29 SkFixed fX; 30 SkFixed fDX; 31 int32_t fFirstY; 32 int32_t fLastY; 33 int8_t fCurveCount; // only used by kQuad(+) and kCubic(-) 34 uint8_t fCurveShift; // appled to all Dx/DDx/DDDx except for fCubicDShift exception 35 uint8_t fCubicDShift; // applied to fCDx and fCDy only in cubic 36 int8_t fWinding; // 1 or -1 37 38 int setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip, int shiftUp); 39 // call this version if you know you don't have a clip 40 inline int setLine(const SkPoint& p0, const SkPoint& p1, int shiftUp); 41 inline int updateLine(SkFixed ax, SkFixed ay, SkFixed bx, SkFixed by); 42 void chopLineWithClip(const SkIRect& clip); 43 44 inline bool intersectsClip(const SkIRect& clip) const { 45 SkASSERT(fFirstY < clip.fBottom); 46 return fLastY >= clip.fTop; 47 } 48 49 #ifdef SK_DEBUG 50 void dump() const { 51 SkDebugf("edge: firstY:%d lastY:%d x:%g dx:%g w:%d\n", fFirstY, fLastY, SkFixedToFloat(fX), SkFixedToFloat(fDX), fWinding); 52 } 53 54 void validate() const { 55 SkASSERT(fPrev && fNext); 56 SkASSERT(fPrev->fNext == this); 57 SkASSERT(fNext->fPrev == this); 58 59 SkASSERT(fFirstY <= fLastY); 60 SkASSERT(SkAbs32(fWinding) == 1); 61 } 62 #endif 63 }; 64 65 struct SkQuadraticEdge : public SkEdge { 66 SkFixed fQx, fQy; 67 SkFixed fQDx, fQDy; 68 SkFixed fQDDx, fQDDy; 69 SkFixed fQLastX, fQLastY; 70 71 bool setQuadraticWithoutUpdate(const SkPoint pts[3], int shiftUp); 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 bool setCubicWithoutUpdate(const SkPoint pts[4], int shiftUp, bool sortY = true); 84 int setCubic(const SkPoint pts[4], 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_RASTERIZE_EVEN_ROUNDING 93 x0 = SkScalarRoundToFDot6(p0.fX, shift); 94 y0 = SkScalarRoundToFDot6(p0.fY, shift); 95 x1 = SkScalarRoundToFDot6(p1.fX, shift); 96 y1 = SkScalarRoundToFDot6(p1.fY, shift); 97 #else 98 float scale = float(1 << (shift + 6)); 99 x0 = int(p0.fX * scale); 100 y0 = int(p0.fY * scale); 101 x1 = int(p1.fX * scale); 102 y1 = int(p1.fY * scale); 103 #endif 104 } 105 106 int winding = 1; 107 108 if (y0 > y1) { 109 SkTSwap(x0, x1); 110 SkTSwap(y0, y1); 111 winding = -1; 112 } 113 114 int top = SkFDot6Round(y0); 115 int bot = SkFDot6Round(y1); 116 117 // are we a zero-height line? 118 if (top == bot) { 119 return 0; 120 } 121 122 SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0); 123 const SkFDot6 dy = SkEdge_Compute_DY(top, y0); 124 125 fX = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy)); // + SK_Fixed1/2 126 fDX = slope; 127 fFirstY = top; 128 fLastY = bot - 1; 129 fCurveCount = 0; 130 fWinding = SkToS8(winding); 131 fCurveShift = 0; 132 return 1; 133 } 134 135 #endif 136
