This repository has been archived by the owner on Feb 11, 2021. It is now read-only.
SDL_rect.c
1
2
/*
SDL - Simple DirectMedia Layer
3
Copyright (C) 1997-2010 Sam Lantinga
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Sam Lantinga
slouken@libsdl.org
*/
#include "SDL_config.h"
24
#include "SDL_rect.h"
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
SDL_bool
SDL_HasIntersection(const SDL_Rect * A, const SDL_Rect * B)
{
int Amin, Amax, Bmin, Bmax;
/* Horizontal intersection */
Amin = A->x;
Amax = Amin + A->w;
Bmin = B->x;
Bmax = Bmin + B->w;
if (Bmin > Amin)
Amin = Bmin;
if (Bmax < Amax)
Amax = Bmax;
if (Amax <= Amin)
return SDL_FALSE;
/* Vertical intersection */
Amin = A->y;
Amax = Amin + A->h;
Bmin = B->y;
Bmax = Bmin + B->h;
if (Bmin > Amin)
Amin = Bmin;
if (Bmax < Amax)
Amax = Bmax;
if (Amax <= Amin)
return SDL_FALSE;
return SDL_TRUE;
}
SDL_bool
SDL_IntersectRect(const SDL_Rect * A, const SDL_Rect * B, SDL_Rect * result)
{
int Amin, Amax, Bmin, Bmax;
/* Horizontal intersection */
Amin = A->x;
Amax = Amin + A->w;
Bmin = B->x;
Bmax = Bmin + B->w;
if (Bmin > Amin)
Amin = Bmin;
result->x = Amin;
if (Bmax < Amax)
Amax = Bmax;
result->w = Amax - Amin;
/* Vertical intersection */
Amin = A->y;
Amax = Amin + A->h;
Bmin = B->y;
Bmax = Bmin + B->h;
if (Bmin > Amin)
Amin = Bmin;
result->y = Amin;
if (Bmax < Amax)
Amax = Bmax;
result->h = Amax - Amin;
return !SDL_RectEmpty(result);
}
void
SDL_UnionRect(const SDL_Rect * A, const SDL_Rect * B, SDL_Rect * result)
{
int Amin, Amax, Bmin, Bmax;
/* Horizontal union */
Amin = A->x;
Amax = Amin + A->w;
Bmin = B->x;
Bmax = Bmin + B->w;
if (Bmin < Amin)
Amin = Bmin;
result->x = Amin;
if (Bmax > Amax)
Amax = Bmax;
result->w = Amax - Amin;
/* Vertical intersection */
Amin = A->y;
Amax = Amin + A->h;
Bmin = B->y;
Bmax = Bmin + B->h;
if (Bmin < Amin)
Amin = Bmin;
result->y = Amin;
if (Bmax > Amax)
Amax = Bmax;
result->h = Amax - Amin;
}
120
121
122
123
SDL_bool
SDL_EnclosePoints(const SDL_Point * points, int count, const SDL_Rect * clip,
SDL_Rect * result)
{
124
125
126
127
int minx = 0;
int miny = 0;
int maxx = 0;
int maxy = 0;
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
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
int x, y, i;
if (count < 1) {
return SDL_FALSE;
}
if (clip) {
SDL_bool added = SDL_FALSE;
int clip_minx = clip->x;
int clip_miny = clip->y;
int clip_maxx = clip->x+clip->w-1;
int clip_maxy = clip->y+clip->h-1;
for (i = 0; i < count; ++i) {
x = points[i].x;
y = points[i].y;
if (x < clip_minx || x > clip_maxx ||
y < clip_miny || y > clip_maxy) {
continue;
}
if (!added) {
minx = maxx = x;
miny = maxy = y;
added = SDL_TRUE;
continue;
}
if (x < minx) {
minx = x;
} else if (x > maxx) {
maxx = x;
}
if (y < miny) {
miny = y;
} else if (y > maxy) {
maxy = y;
}
}
if (!added) {
return SDL_FALSE;
}
} else {
/* No clipping, always add the first point */
minx = maxx = points[0].x;
miny = maxy = points[0].y;
for (i = 1; i < count; ++i) {
x = points[i].x;
y = points[i].y;
if (x < minx) {
minx = x;
} else if (x > maxx) {
maxx = x;
}
if (y < miny) {
miny = y;
} else if (y > maxy) {
maxy = y;
}
}
}
if (result) {
result->x = minx;
result->y = miny;
result->w = (maxx-minx)+1;
result->h = (maxy-miny)+1;
}
return SDL_TRUE;
}
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
/* Use the Cohen-Sutherland algorithm for line clipping */
#define CODE_BOTTOM 1
#define CODE_TOP 2
#define CODE_LEFT 4
#define CODE_RIGHT 8
static int ComputeOutCode(const SDL_Rect * rect, int x, int y)
{
int code = 0;
if (y < 0) {
code |= CODE_TOP;
} else if (y >= rect->y + rect->h) {
code |= CODE_BOTTOM;
}
if (x < 0) {
code |= CODE_LEFT;
} else if (x >= rect->x + rect->w) {
code |= CODE_RIGHT;
}
return code;
}
222
SDL_bool
223
224
SDL_IntersectRectAndLine(const SDL_Rect * rect, int *X1, int *Y1, int *X2,
int *Y2)
226
227
int x = 0;
int y = 0;
228
229
230
231
232
233
int x1, y1;
int x2, y2;
int rectx1;
int recty1;
int rectx2;
int recty2;
234
int outcode1, outcode2;
235
236
if (!rect || !X1 || !Y1 || !X2 || !Y2) {
237
return SDL_FALSE;
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
}
x1 = *X1;
y1 = *Y1;
x2 = *X2;
y2 = *Y2;
rectx1 = rect->x;
recty1 = rect->y;
rectx2 = rect->x + rect->w - 1;
recty2 = rect->y + rect->h - 1;
/* Check to see if entire line is inside rect */
if (x1 >= rectx1 && x1 <= rectx2 && x2 >= rectx1 && x2 <= rectx2 &&
y1 >= recty1 && y1 <= recty2 && y2 >= recty1 && y2 <= recty2) {
return SDL_TRUE;
}
255
/* Check to see if entire line is to one side of rect */
256
if ((x1 < rectx1 && x2 < rectx1) || (x1 > rectx2 && x2 > rectx2) ||
257
(y1 < recty1 && y2 < recty1) || (y1 > recty2 && y2 > recty2)) {
258
259
260
return SDL_FALSE;
}
261
if (y1 == y2) {
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
/* Horizontal line, easy to clip */
if (x1 < rectx1) {
*X1 = rectx1;
} else if (x1 > rectx2) {
*X1 = rectx2;
}
if (x2 < rectx1) {
*X2 = rectx1;
} else if (x2 > rectx2) {
*X2 = rectx2;
}
return SDL_TRUE;
}
if (x1 == x2) {
/* Vertical line, easy to clip */
if (y1 < recty1) {
*Y1 = recty1;
} else if (y1 > recty2) {
*Y1 = recty2;
}
if (y2 < recty1) {
*Y2 = recty1;
} else if (y2 > recty2) {
*Y2 = recty2;
}
return SDL_TRUE;
}
291
292
293
294
295
296
/* More complicated Cohen-Sutherland algorithm */
outcode1 = ComputeOutCode(rect, x1, y1);
outcode2 = ComputeOutCode(rect, x2, y2);
while (outcode1 || outcode2) {
if (outcode1 & outcode2) {
return SDL_FALSE;
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
if (outcode1) {
if (outcode1 & CODE_TOP) {
y = recty1;
x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
} else if (outcode1 & CODE_BOTTOM) {
y = recty2;
x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
} else if (outcode1 & CODE_LEFT) {
x = rectx1;
y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
} else if (outcode1 & CODE_RIGHT) {
x = rectx2;
y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
}
x1 = x;
y1 = y;
outcode1 = ComputeOutCode(rect, x, y);
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
if (outcode2 & CODE_TOP) {
y = recty1;
x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
} else if (outcode2 & CODE_BOTTOM) {
y = recty2;
x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
} else if (outcode2 & CODE_LEFT) {
x = rectx1;
y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
} else if (outcode2 & CODE_RIGHT) {
x = rectx2;
y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
}
x2 = x;
y2 = y;
outcode2 = ComputeOutCode(rect, x, y);
333
334
}
}
335
336
337
338
339
*X1 = x1;
*Y1 = y1;
*X2 = x2;
*Y2 = y2;
return SDL_TRUE;
340
341
}
342
/* vi: set ts=4 sw=4 expandtab: */