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 #ifndef SkEdge_DEFINED
9 #define SkEdge_DEFINED
10
11 #include "include/core/SkMath.h"
12 #include "include/core/SkRect.h"
13 #include "include/private/SkTo.h"
14 #include "src/core/SkFDot6.h"
15
16 #include <utility>
17
18 // This correctly favors the lower-pixel when y0 is on a 1/2 pixel boundary
19 #define SkEdge_Compute_DY(top, y0) (SkLeftShift(top, 6) + 32 - (y0))
20
21 struct SkEdge {
22 enum Type {
23 kLine_Type,
24 kQuad_Type,
25 kCubic_Type
26 };
27
28 SkEdge* fNext;
29 SkEdge* fPrev;
30
31 SkFixed fX;
32 SkFixed fDX;
33 int32_t fFirstY;
34 int32_t fLastY;
35 int8_t fCurveCount; // only used by kQuad(+) and kCubic(-)
36 uint8_t fCurveShift; // appled to all Dx/DDx/DDDx except for fCubicDShift exception
37 uint8_t fCubicDShift; // applied to fCDx and fCDy only in cubic
38 int8_t fWinding; // 1 or -1
39
40 int setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip, 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 bool setQuadraticWithoutUpdate(const SkPoint pts[3], int shiftUp);
74 int setQuadratic(const SkPoint pts[3], int shiftUp);
75 int updateQuadratic();
76 };
77
78 struct SkCubicEdge : public SkEdge {
79 SkFixed fCx, fCy;
80 SkFixed fCDx, fCDy;
81 SkFixed fCDDx, fCDDy;
82 SkFixed fCDDDx, fCDDDy;
83 SkFixed fCLastX, fCLastY;
84
85 bool setCubicWithoutUpdate(const SkPoint pts[4], int shiftUp, bool sortY = true);
86 int setCubic(const SkPoint pts[4], int shiftUp);
87 int updateCubic();
88 };
89
setLine(const SkPoint & p0,const SkPoint & p1,int shift)90 int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, int shift) {
91 SkFDot6 x0, y0, x1, y1;
92
93 {
94 #ifdef SK_RASTERIZE_EVEN_ROUNDING
95 x0 = SkScalarRoundToFDot6(p0.fX, shift);
96 y0 = SkScalarRoundToFDot6(p0.fY, shift);
97 x1 = SkScalarRoundToFDot6(p1.fX, shift);
98 y1 = SkScalarRoundToFDot6(p1.fY, shift);
99 #else
100 float scale = float(1 << (shift + 6));
101 x0 = int(p0.fX * scale);
102 y0 = int(p0.fY * scale);
103 x1 = int(p1.fX * scale);
104 y1 = int(p1.fY * scale);
105 #endif
106 }
107
108 int winding = 1;
109
110 if (y0 > y1) {
111 using std::swap;
112 swap(x0, x1);
113 swap(y0, y1);
114 winding = -1;
115 }
116
117 int top = SkFDot6Round(y0);
118 int bot = SkFDot6Round(y1);
119
120 // are we a zero-height line?
121 if (top == bot) {
122 return 0;
123 }
124
125 SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0);
126 const SkFDot6 dy = SkEdge_Compute_DY(top, y0);
127
128 fX = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy)); // + SK_Fixed1/2
129 fDX = slope;
130 fFirstY = top;
131 fLastY = bot - 1;
132 fCurveCount = 0;
133 fWinding = SkToS8(winding);
134 fCurveShift = 0;
135 return 1;
136 }
137
138 #endif
139