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39 | |
40 | #ifndef QPOLYGONCLIPPER_P_H |
41 | #define QPOLYGONCLIPPER_P_H |
42 | |
43 | // |
44 | // W A R N I N G |
45 | // ------------- |
46 | // |
47 | // This file is not part of the Qt API. It exists for the convenience |
48 | // of other Qt classes. This header file may change from version to |
49 | // version without notice, or even be removed. |
50 | // |
51 | // We mean it. |
52 | // |
53 | |
54 | #include <QtGui/private/qtguiglobal_p.h> |
55 | #include "private/qdatabuffer_p.h" |
56 | |
57 | QT_BEGIN_NAMESPACE |
58 | |
59 | /* based on sutherland-hodgman line-by-line clipping, as described in |
60 | Computer Graphics and Principles */ |
61 | template <typename InType, typename OutType, typename CastType> class QPolygonClipper |
62 | { |
63 | public: |
64 | QPolygonClipper() : |
65 | buffer1(0), buffer2(0) |
66 | { |
67 | x1 = y1 = x2 = y2 = 0; |
68 | } |
69 | |
70 | ~QPolygonClipper() |
71 | { |
72 | } |
73 | |
74 | void setBoundingRect(const QRect bounds) |
75 | { |
76 | x1 = bounds.x(); |
77 | x2 = bounds.x() + bounds.width(); |
78 | y1 = bounds.y(); |
79 | y2 = bounds.y() + bounds.height(); |
80 | } |
81 | |
82 | QRect boundingRect() |
83 | { |
84 | return QRect(QPoint(x1, y1), QPoint(x2, y2)); |
85 | } |
86 | |
87 | inline OutType intersectLeft(const OutType &p1, const OutType &p2) |
88 | { |
89 | OutType t; |
90 | qreal dy = (p1.y - p2.y) / qreal(p1.x - p2.x); |
91 | t.x = x1; |
92 | t.y = static_cast<CastType>(p2.y + (x1 - p2.x) * dy); |
93 | return t; |
94 | } |
95 | |
96 | |
97 | inline OutType intersectRight(const OutType &p1, const OutType &p2) |
98 | { |
99 | OutType t; |
100 | qreal dy = (p1.y - p2.y) / qreal(p1.x - p2.x); |
101 | t.x = x2; |
102 | t.y = static_cast<CastType>(p2.y + (x2 - p2.x) * dy); |
103 | return t; |
104 | } |
105 | |
106 | |
107 | inline OutType intersectTop(const OutType &p1, const OutType &p2) |
108 | { |
109 | OutType t; |
110 | qreal dx = (p1.x - p2.x) / qreal(p1.y - p2.y); |
111 | t.x = static_cast<CastType>(p2.x + (y1 - p2.y) * dx); |
112 | t.y = y1; |
113 | return t; |
114 | } |
115 | |
116 | |
117 | inline OutType intersectBottom(const OutType &p1, const OutType &p2) |
118 | { |
119 | OutType t; |
120 | qreal dx = (p1.x - p2.x) / qreal(p1.y - p2.y); |
121 | t.x = static_cast<CastType>(p2.x + (y2 - p2.y) * dx); |
122 | t.y = y2; |
123 | return t; |
124 | } |
125 | |
126 | |
127 | void clipPolygon(const InType *inPoints, int inCount, OutType **outPoints, int *outCount, |
128 | bool closePolygon = true) |
129 | { |
130 | Q_ASSERT(outPoints); |
131 | Q_ASSERT(outCount); |
132 | |
133 | if (inCount < 2) { |
134 | *outCount = 0; |
135 | return; |
136 | } |
137 | |
138 | buffer1.reset(); |
139 | buffer2.reset(); |
140 | |
141 | QDataBuffer<OutType> *source = &buffer1; |
142 | QDataBuffer<OutType> *clipped = &buffer2; |
143 | |
144 | // Gather some info since we are iterating through the points anyway.. |
145 | bool doLeft = false, doRight = false, doTop = false, doBottom = false; |
146 | OutType ot; |
147 | for (int i=0; i<inCount; ++i) { |
148 | ot = inPoints[i]; |
149 | clipped->add(ot); |
150 | |
151 | if (ot.x < x1) |
152 | doLeft = true; |
153 | else if (ot.x > x2) |
154 | doRight = true; |
155 | if (ot.y < y1) |
156 | doTop = true; |
157 | else if (ot.y > y2) |
158 | doBottom = true; |
159 | } |
160 | |
161 | if (doLeft && clipped->size() > 1) { |
162 | QDataBuffer<OutType> *tmp = source; |
163 | source = clipped; |
164 | clipped = tmp; |
165 | clipped->reset(); |
166 | int lastPos, start; |
167 | if (closePolygon) { |
168 | lastPos = source->size() - 1; |
169 | start = 0; |
170 | } else { |
171 | lastPos = 0; |
172 | start = 1; |
173 | if (source->at(0).x >= x1) |
174 | clipped->add(source->at(0)); |
175 | } |
176 | for (int i=start; i<inCount; ++i) { |
177 | const OutType &cpt = source->at(i); |
178 | const OutType &ppt = source->at(lastPos); |
179 | |
180 | if (cpt.x >= x1) { |
181 | if (ppt.x >= x1) { |
182 | clipped->add(cpt); |
183 | } else { |
184 | clipped->add(intersectLeft(cpt, ppt)); |
185 | clipped->add(cpt); |
186 | } |
187 | } else if (ppt.x >= x1) { |
188 | clipped->add(intersectLeft(cpt, ppt)); |
189 | } |
190 | lastPos = i; |
191 | } |
192 | } |
193 | |
194 | if (doRight && clipped->size() > 1) { |
195 | QDataBuffer<OutType> *tmp = source; |
196 | source = clipped; |
197 | clipped = tmp; |
198 | clipped->reset(); |
199 | int lastPos, start; |
200 | if (closePolygon) { |
201 | lastPos = source->size() - 1; |
202 | start = 0; |
203 | } else { |
204 | lastPos = 0; |
205 | start = 1; |
206 | if (source->at(0).x <= x2) |
207 | clipped->add(source->at(0)); |
208 | } |
209 | for (int i=start; i<source->size(); ++i) { |
210 | const OutType &cpt = source->at(i); |
211 | const OutType &ppt = source->at(lastPos); |
212 | |
213 | if (cpt.x <= x2) { |
214 | if (ppt.x <= x2) { |
215 | clipped->add(cpt); |
216 | } else { |
217 | clipped->add(intersectRight(cpt, ppt)); |
218 | clipped->add(cpt); |
219 | } |
220 | } else if (ppt.x <= x2) { |
221 | clipped->add(intersectRight(cpt, ppt)); |
222 | } |
223 | |
224 | lastPos = i; |
225 | } |
226 | |
227 | } |
228 | |
229 | if (doTop && clipped->size() > 1) { |
230 | QDataBuffer<OutType> *tmp = source; |
231 | source = clipped; |
232 | clipped = tmp; |
233 | clipped->reset(); |
234 | int lastPos, start; |
235 | if (closePolygon) { |
236 | lastPos = source->size() - 1; |
237 | start = 0; |
238 | } else { |
239 | lastPos = 0; |
240 | start = 1; |
241 | if (source->at(0).y >= y1) |
242 | clipped->add(source->at(0)); |
243 | } |
244 | for (int i=start; i<source->size(); ++i) { |
245 | const OutType &cpt = source->at(i); |
246 | const OutType &ppt = source->at(lastPos); |
247 | |
248 | if (cpt.y >= y1) { |
249 | if (ppt.y >= y1) { |
250 | clipped->add(cpt); |
251 | } else { |
252 | clipped->add(intersectTop(cpt, ppt)); |
253 | clipped->add(cpt); |
254 | } |
255 | } else if (ppt.y >= y1) { |
256 | clipped->add(intersectTop(cpt, ppt)); |
257 | } |
258 | |
259 | lastPos = i; |
260 | } |
261 | } |
262 | |
263 | if (doBottom && clipped->size() > 1) { |
264 | QDataBuffer<OutType> *tmp = source; |
265 | source = clipped; |
266 | clipped = tmp; |
267 | clipped->reset(); |
268 | int lastPos, start; |
269 | if (closePolygon) { |
270 | lastPos = source->size() - 1; |
271 | start = 0; |
272 | } else { |
273 | lastPos = 0; |
274 | start = 1; |
275 | if (source->at(0).y <= y2) |
276 | clipped->add(source->at(0)); |
277 | } |
278 | for (int i=start; i<source->size(); ++i) { |
279 | const OutType &cpt = source->at(i); |
280 | const OutType &ppt = source->at(lastPos); |
281 | |
282 | if (cpt.y <= y2) { |
283 | if (ppt.y <= y2) { |
284 | clipped->add(cpt); |
285 | } else { |
286 | clipped->add(intersectBottom(cpt, ppt)); |
287 | clipped->add(cpt); |
288 | } |
289 | } else if (ppt.y <= y2) { |
290 | clipped->add(intersectBottom(cpt, ppt)); |
291 | } |
292 | lastPos = i; |
293 | } |
294 | } |
295 | |
296 | if (closePolygon && clipped->size() > 0) { |
297 | // close clipped polygon |
298 | if (clipped->at(0).x != clipped->at(clipped->size()-1).x || |
299 | clipped->at(0).y != clipped->at(clipped->size()-1).y) { |
300 | OutType ot = clipped->at(0); |
301 | clipped->add(ot); |
302 | } |
303 | } |
304 | *outCount = clipped->size(); |
305 | *outPoints = clipped->data(); |
306 | } |
307 | |
308 | private: |
309 | int x1, x2, y1, y2; |
310 | QDataBuffer<OutType> buffer1; |
311 | QDataBuffer<OutType> buffer2; |
312 | }; |
313 | |
314 | QT_END_NAMESPACE |
315 | |
316 | #endif // QPOLYGONCLIPPER_P_H |
317 |
Warning: That file was not part of the compilation database. It may have many parsing errors.