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
intersectsClipSkEdge46 inline bool intersectsClip(const SkIRect& clip) const {
47 SkASSERT(fFirstY < clip.fBottom);
48 return fLastY >= clip.fTop;
49 }
50
51 #ifdef SK_DEBUG
dumpSkEdge52 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
validateSkEdge56 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
setLine(const SkPoint & p0,const SkPoint & p1,int shift)88 int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, int shift) {
89 SkFDot6 x0, y0, x1, y1;
90
91 {
92 float scale = float(1 << (shift + 6));
93 x0 = int(p0.fX * scale);
94 y0 = int(p0.fY * scale);
95 x1 = int(p1.fX * scale);
96 y1 = int(p1.fY * scale);
97 }
98
99 int winding = 1;
100
101 if (y0 > y1) {
102 SkTSwap(x0, x1);
103 SkTSwap(y0, y1);
104 winding = -1;
105 }
106
107 int top = SkFDot6Round(y0);
108 int bot = SkFDot6Round(y1);
109
110 // are we a zero-height line?
111 if (top == bot) {
112 return 0;
113 }
114
115 SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0);
116 const int dy = SkEdge_Compute_DY(top, y0);
117
118 fX = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy)); // + SK_Fixed1/2
119 fDX = slope;
120 fFirstY = top;
121 fLastY = bot - 1;
122 fCurveCount = 0;
123 fWinding = SkToS8(winding);
124 fCurveShift = 0;
125 return 1;
126 }
127
128
129 #endif
130