1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
#include "SkLineClipper.h"
// return X coordinate of intersection with horizontal line at Y
static SkScalar sect_with_horizontal(const SkPoint src[2], SkScalar Y) {
SkScalar dy = src[1].fY - src[0].fY;
if (SkScalarNearlyZero(dy)) {
return SkScalarAve(src[0].fX, src[1].fX);
} else {
return src[0].fX + SkScalarMulDiv(Y - src[0].fY, src[1].fX - src[0].fX,
dy);
}
}
// return Y coordinate of intersection with vertical line at X
static SkScalar sect_with_vertical(const SkPoint src[2], SkScalar X) {
SkScalar dx = src[1].fX - src[0].fX;
if (SkScalarNearlyZero(dx)) {
return SkScalarAve(src[0].fY, src[1].fY);
} else {
return src[0].fY + SkScalarMulDiv(X - src[0].fX, src[1].fY - src[0].fY,
dx);
}
}
///////////////////////////////////////////////////////////////////////////////
bool SkLineClipper::IntersectLine(const SkPoint src[2], const SkRect& clip,
SkPoint dst[2]) {
SkRect bounds;
bounds.set(src, 2);
if (bounds.fLeft >= clip.fRight || clip.fLeft >= bounds.fRight ||
bounds.fTop >= clip.fBottom || clip.fTop >= bounds.fBottom) {
return false;
}
if (clip.contains(bounds)) {
if (src != dst) {
memcpy(dst, src, 2 * sizeof(SkPoint));
}
return true;
}
int index0, index1;
if (src[0].fY < src[1].fY) {
index0 = 0;
index1 = 1;
} else {
index0 = 1;
index1 = 0;
}
SkPoint tmp[2];
memcpy(tmp, src, sizeof(tmp));
// now compute Y intersections
if (tmp[index0].fY < clip.fTop) {
tmp[index0].set(sect_with_horizontal(src, clip.fTop), clip.fTop);
}
if (tmp[index1].fY > clip.fBottom) {
tmp[index1].set(sect_with_horizontal(src, clip.fBottom), clip.fBottom);
}
if (tmp[0].fX < tmp[1].fX) {
index0 = 0;
index1 = 1;
} else {
index0 = 1;
index1 = 0;
}
// check for quick-reject in X again, now that we may have been chopped
if (tmp[index1].fX <= clip.fLeft || tmp[index0].fX >= clip.fRight) {
return false;
}
if (tmp[index0].fX < clip.fLeft) {
tmp[index0].set(clip.fLeft, sect_with_vertical(src, clip.fLeft));
}
if (tmp[index1].fX > clip.fRight) {
tmp[index1].set(clip.fRight, sect_with_vertical(src, clip.fRight));
}
memcpy(dst, tmp, sizeof(tmp));
return true;
}
int SkLineClipper::ClipLine(const SkPoint pts[], const SkRect& clip,
SkPoint lines[]) {
int index0, index1;
if (pts[0].fY < pts[1].fY) {
index0 = 0;
index1 = 1;
} else {
index0 = 1;
index1 = 0;
}
// Check if we're completely clipped out in Y (above or below
if (pts[index1].fY <= clip.fTop) { // we're above the clip
return 0;
}
if (pts[index0].fY >= clip.fBottom) { // we're below the clip
return 0;
}
// Chop in Y to produce a single segment, stored in tmp[0..1]
SkPoint tmp[2];
memcpy(tmp, pts, sizeof(tmp));
// now compute intersections
if (pts[index0].fY < clip.fTop) {
tmp[index0].set(sect_with_horizontal(pts, clip.fTop), clip.fTop);
}
if (tmp[index1].fY > clip.fBottom) {
tmp[index1].set(sect_with_horizontal(pts, clip.fBottom), clip.fBottom);
}
// Chop it into 1..3 segments that are wholly within the clip in X.
// temp storage for up to 3 segments
SkPoint resultStorage[kMaxPoints];
SkPoint* result; // points to our results, either tmp or resultStorage
int lineCount = 1;
bool reverse;
if (pts[0].fX < pts[1].fX) {
index0 = 0;
index1 = 1;
reverse = false;
} else {
index0 = 1;
index1 = 0;
reverse = true;
}
if (tmp[index1].fX <= clip.fLeft) { // wholly to the left
tmp[0].fX = tmp[1].fX = clip.fLeft;
result = tmp;
reverse = false;
} else if (tmp[index0].fX >= clip.fRight) { // wholly to the right
tmp[0].fX = tmp[1].fX = clip.fRight;
result = tmp;
reverse = false;
} else {
result = resultStorage;
SkPoint* r = result;
if (tmp[index0].fX < clip.fLeft) {
r->set(clip.fLeft, tmp[index0].fY);
r += 1;
r->set(clip.fLeft, sect_with_vertical(pts, clip.fLeft));
} else {
*r = tmp[index0];
}
r += 1;
if (tmp[index1].fX > clip.fRight) {
r->set(clip.fRight, sect_with_vertical(pts, clip.fRight));
r += 1;
r->set(clip.fRight, tmp[index1].fY);
} else {
*r = tmp[index1];
}
lineCount = r - result;
}
// Now copy the results into the caller's lines[] parameter
if (reverse) {
// copy the pts in reverse order to maintain winding order
for (int i = 0; i <= lineCount; i++) {
lines[lineCount - i] = result[i];
}
} else {
memcpy(lines, result, (lineCount + 1) * sizeof(SkPoint));
}
return lineCount;
}
|
