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| 1 | /* | ||
| 2 | * Copyright (c) 1998, 2000, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package sun.java2d; | ||
| 27 | |||
| 28 | import java.util.Comparator; | ||
| 29 | import java.util.Collections; | ||
| 30 | import java.util.Iterator; | ||
| 31 | import java.util.List; | ||
| 32 | import java.util.Vector; | ||
| 33 | |||
| 34 | /** | ||
| 35 | * Maintains a list of half-open intervals, called Spans. | ||
| 36 | * A Span can be tested against the list of Spans | ||
| 37 | * for intersection. | ||
| 38 | */ | ||
| 39 | public class Spans { | ||
| 40 | |||
| 41 | /** | ||
| 42 | * This class will sort and collapse its span | ||
| 43 | * entries after this many span additions via | ||
| 44 | * the <code>add</code> method. | ||
| 45 | */ | ||
| 46 | private static final int kMaxAddsSinceSort = 256; | ||
| 47 | |||
| 48 | /** | ||
| 49 | * Holds a list of individual | ||
| 50 | * Span instances. | ||
| 51 | */ | ||
| 52 | private List mSpans = new Vector(kMaxAddsSinceSort); | ||
| 53 | |||
| 54 | /** | ||
| 55 | * The number of <code>Span</code> | ||
| 56 | * instances that have been added | ||
| 57 | * to this object without a sort | ||
| 58 | * and collapse taking place. | ||
| 59 | */ | ||
| 60 | private int mAddsSinceSort = 0; | ||
| 61 | |||
| 62 | public Spans() { | ||
| 63 | |||
| 64 | } | ||
| 65 | |||
| 66 | /** | ||
| 67 | * Add a span covering the half open interval | ||
| 68 | * including <code>start</code> up to | ||
| 69 | * but not including <code>end</code>. | ||
| 70 | */ | ||
| 71 | public void add(float start, float end) { | ||
| 72 | |||
| 73 | if (mSpans != null) { | ||
| 74 | mSpans.add(new Span(start, end)); | ||
| 75 | |||
| 76 | if (++mAddsSinceSort >= kMaxAddsSinceSort) { | ||
| 77 | sortAndCollapse(); | ||
| 78 | } | ||
| 79 | } | ||
| 80 | } | ||
| 81 | |||
| 82 | /** | ||
| 83 | * Add a span which covers the entire range. | ||
| 84 | * This call is logically equivalent to | ||
| 85 | * <code>add(Float.NEGATIVE_INFINITY, Float.POSITIVE_INFINITY)</code> | ||
| 86 | * The result of making this call is that | ||
| 87 | * all future <code>add</code> calls are ignored | ||
| 88 | * and the <code>intersects</code> method always | ||
| 89 | * returns true. | ||
| 90 | */ | ||
| 91 | public void addInfinite() { | ||
| 92 | mSpans = null; | ||
| 93 | } | ||
| 94 | |||
| 95 | /** | ||
| 96 | * Returns true if the span defined by the half-open | ||
| 97 | * interval from <code>start</code> up to, | ||
| 98 | * but not including, <code>end</code> intersects | ||
| 99 | * any of the spans defined by this instance. | ||
| 100 | */ | ||
| 101 | public boolean intersects(float start, float end) { | ||
| 102 | boolean doesIntersect; | ||
| 103 | |||
| 104 | if (mSpans != null) { | ||
| 105 | |||
| 106 | /* If we have added any spans since we last | ||
| 107 | * sorted and collapsed our list of spans | ||
| 108 | * then we need to resort and collapse. | ||
| 109 | */ | ||
| 110 | if (mAddsSinceSort > 0) { | ||
| 111 | sortAndCollapse(); | ||
| 112 | } | ||
| 113 | |||
| 114 | /* The SpanIntersection comparator considers | ||
| 115 | * two spans equal if they intersect. If | ||
| 116 | * the search finds a match then we have an | ||
| 117 | * intersection. | ||
| 118 | */ | ||
| 119 | int found = Collections.binarySearch(mSpans, | ||
| 120 | new Span(start, end), | ||
| 121 | SpanIntersection.instance); | ||
| 122 | |||
| 123 | doesIntersect = found >= 0; | ||
| 124 | |||
| 125 | /* The addInfinite() method has been invoked so | ||
| 126 | * everything intersect this instance. | ||
| 127 | */ | ||
| 128 | } else { | ||
| 129 | doesIntersect = true; | ||
| 130 | } | ||
| 131 | |||
| 132 | return doesIntersect; | ||
| 133 | } | ||
| 134 | |||
| 135 | /** | ||
| 136 | * Sort the spans in ascending order by their | ||
| 137 | * start position. After the spans are sorted | ||
| 138 | * collapse any spans that intersect into a | ||
| 139 | * single span. The result is a sorted, | ||
| 140 | * non-overlapping list of spans. | ||
| 141 | */ | ||
| 142 | private void sortAndCollapse() { | ||
| 143 | |||
| 144 | Collections.sort(mSpans); | ||
| 145 | mAddsSinceSort = 0; | ||
| 146 | |||
| 147 | Iterator iter = mSpans.iterator(); | ||
| 148 | |||
| 149 | /* Have 'span' start at the first span in | ||
| 150 | * the collection. The collection may be empty | ||
| 151 | * so we're careful. | ||
| 152 | */ | ||
| 153 | Span span = null; | ||
| 154 | if (iter.hasNext()) { | ||
| 155 | span = (Span) iter.next(); | ||
| 156 | } | ||
| 157 | |||
| 158 | /* Loop over the spans collapsing those that intersect | ||
| 159 | * into a single span. | ||
| 160 | */ | ||
| 161 | while (iter.hasNext()) { | ||
| 162 | |||
| 163 | Span nextSpan = (Span) iter.next(); | ||
| 164 | |||
| 165 | /* The spans are in ascending start position | ||
| 166 | * order and so the next span's starting point | ||
| 167 | * is either in the span we are trying to grow | ||
| 168 | * or it is beyond the first span and thus the | ||
| 169 | * two spans do not intersect. | ||
| 170 | * | ||
| 171 | * span: <----------< | ||
| 172 | * nextSpan: <------ (intersects) | ||
| 173 | * nextSpan: <------ (doesn't intersect) | ||
| 174 | * | ||
| 175 | * If the spans intersect then we'll remove | ||
| 176 | * nextSpan from the list. If nextSpan's | ||
| 177 | * ending was beyond the first's then | ||
| 178 | * we extend the first. | ||
| 179 | * | ||
| 180 | * span: <----------< | ||
| 181 | * nextSpan: <-----< (don't change span) | ||
| 182 | * nextSpan: <-----------< (grow span) | ||
| 183 | */ | ||
| 184 | |||
| 185 | if (span.subsume(nextSpan)) { | ||
| 186 | iter.remove(); | ||
| 187 | |||
| 188 | /* The next span did not intersect the current | ||
| 189 | * span and so it can not be collapsed. Instead | ||
| 190 | * it becomes the start of the next set of spans | ||
| 191 | * to be collapsed. | ||
| 192 | */ | ||
| 193 | } else { | ||
| 194 | span = nextSpan; | ||
| 195 | } | ||
| 196 | } | ||
| 197 | } | ||
| 198 | |||
| 199 | /* | ||
| 200 | // For debugging. | ||
| 201 | |||
| 202 | private void printSpans() { | ||
| 203 | System.out.println("----------"); | ||
| 204 | if (mSpans != null) { | ||
| 205 | Iterator iter = mSpans.iterator(); | ||
| 206 | while (iter.hasNext()) { | ||
| 207 | Span span = (Span) iter.next(); | ||
| 208 | System.out.println(span); | ||
| 209 | } | ||
| 210 | } | ||
| 211 | System.out.println("----------"); | ||
| 212 | |||
| 213 | } | ||
| 214 | */ | ||
| 215 | |||
| 216 | /** | ||
| 217 | * Holds a single half-open interval. | ||
| 218 | */ | ||
| 219 | static class Span implements Comparable { | ||
| 220 | |||
| 221 | /** | ||
| 222 | * The span includes the starting point. | ||
| 223 | */ | ||
| 224 | private float mStart; | ||
| 225 | |||
| 226 | /** | ||
| 227 | * The span goes up to but does not include | ||
| 228 | * the ending point. | ||
| 229 | */ | ||
| 230 | private float mEnd; | ||
| 231 | |||
| 232 | /** | ||
| 233 | * Create a half-open interval including | ||
| 234 | * <code>start</code> but not including | ||
| 235 | * <code>end</code>. | ||
| 236 | */ | ||
| 237 | Span(float start, float end) { | ||
| 238 | mStart = start; | ||
| 239 | mEnd = end; | ||
| 240 | } | ||
| 241 | |||
| 242 | /** | ||
| 243 | * Return the start of the <code>Span</code>. | ||
| 244 | * The start is considered part of the | ||
| 245 | * half-open interval. | ||
| 246 | */ | ||
| 247 | final float getStart() { | ||
| 248 | return mStart; | ||
| 249 | } | ||
| 250 | |||
| 251 | /** | ||
| 252 | * Return the end of the <code>Span</code>. | ||
| 253 | * The end is not considered part of the | ||
| 254 | * half-open interval. | ||
| 255 | */ | ||
| 256 | final float getEnd() { | ||
| 257 | return mEnd; | ||
| 258 | } | ||
| 259 | |||
| 260 | /** | ||
| 261 | * Change the initial position of the | ||
| 262 | * <code>Span</code>. | ||
| 263 | */ | ||
| 264 | final void setStart(float start) { | ||
| 265 | mStart = start; | ||
| 266 | } | ||
| 267 | |||
| 268 | /** | ||
| 269 | * Change the terminal position of the | ||
| 270 | * <code>Span</code>. | ||
| 271 | */ | ||
| 272 | final void setEnd(float end) { | ||
| 273 | mEnd = end; | ||
| 274 | } | ||
| 275 | |||
| 276 | /** | ||
| 277 | * Attempt to alter this <code>Span</code> | ||
| 278 | * to include <code>otherSpan</code> without | ||
| 279 | * altering this span's starting position. | ||
| 280 | * If <code>otherSpan</code> can be so consumed | ||
| 281 | * by this <code>Span</code> then <code>true</code> | ||
| 282 | * is returned. | ||
| 283 | */ | ||
| 284 | boolean subsume(Span otherSpan) { | ||
| 285 | |||
| 286 | /* We can only subsume 'otherSpan' if | ||
| 287 | * its starting position lies in our | ||
| 288 | * interval. | ||
| 289 | */ | ||
| 290 | boolean isSubsumed = contains(otherSpan.mStart); | ||
| 291 | |||
| 292 | /* If the other span's starting position | ||
| 293 | * was in our interval and the other span | ||
| 294 | * was longer than this span, then we need | ||
| 295 | * to grow this span to cover the difference. | ||
| 296 | */ | ||
| 297 | if (isSubsumed && otherSpan.mEnd > mEnd) { | ||
| 298 | mEnd = otherSpan.mEnd; | ||
| 299 | } | ||
| 300 | |||
| 301 | return isSubsumed; | ||
| 302 | } | ||
| 303 | |||
| 304 | /** | ||
| 305 | * Return true if the passed in position | ||
| 306 | * lies in the half-open interval defined | ||
| 307 | * by this <code>Span</code>. | ||
| 308 | */ | ||
| 309 | boolean contains(float pos) { | ||
| 310 | return mStart <= pos && pos < mEnd; | ||
| 311 | } | ||
| 312 | |||
| 313 | /** | ||
| 314 | * Rank spans according to their starting | ||
| 315 | * position. The end position is ignored | ||
| 316 | * in this ranking. | ||
| 317 | */ | ||
| 318 | public int compareTo(Object o) { | ||
| 319 | Span otherSpan = (Span) o; | ||
| 320 | float otherStart = otherSpan.getStart(); | ||
| 321 | int result; | ||
| 322 | |||
| 323 | if (mStart < otherStart) { | ||
| 324 | result = -1; | ||
| 325 | } else if (mStart > otherStart) { | ||
| 326 | result = 1; | ||
| 327 | } else { | ||
| 328 | result = 0; | ||
| 329 | } | ||
| 330 | |||
| 331 | return result; | ||
| 332 | } | ||
| 333 | |||
| 334 | public String toString() { | ||
| 335 | return "Span: " + mStart + " to " + mEnd; | ||
| 336 | } | ||
| 337 | |||
| 338 | } | ||
| 339 | |||
| 340 | /** | ||
| 341 | * This class ranks a pair of <code>Span</code> | ||
| 342 | * instances. If the instances intersect they | ||
| 343 | * are deemed equal otherwise they are ranked | ||
| 344 | * by their relative position. Use | ||
| 345 | * <code>SpanIntersection.instance</code> to | ||
| 346 | * get the single instance of this class. | ||
| 347 | */ | ||
| 348 | static class SpanIntersection implements Comparator { | ||
| 349 | |||
| 350 | /** | ||
| 351 | * This class is a Singleton and the following | ||
| 352 | * is the single instance. | ||
| 353 | */ | ||
| 354 | static final SpanIntersection instance = | ||
| 355 | new SpanIntersection(); | ||
| 356 | |||
| 357 | /** | ||
| 358 | * Only this class can create instances of itself. | ||
| 359 | */ | ||
| 360 | private SpanIntersection() { | ||
| 361 | |||
| 362 | } | ||
| 363 | |||
| 364 | public int compare(Object o1, Object o2) { | ||
| 365 | int result; | ||
| 366 | Span span1 = (Span) o1; | ||
| 367 | Span span2 = (Span) o2; | ||
| 368 | |||
| 369 | /* Span 1 is entirely to the left of span2. | ||
| 370 | * span1: <-----< | ||
| 371 | * span2: <-----< | ||
| 372 | */ | ||
| 373 | if (span1.getEnd() <= span2.getStart()) { | ||
| 374 | result = -1; | ||
| 375 | |||
| 376 | /* Span 2 is entirely to the right of span2. | ||
| 377 | * span1: <-----< | ||
| 378 | * span2: <-----< | ||
| 379 | */ | ||
| 380 | } else if (span1.getStart() >= span2.getEnd()) { | ||
| 381 | result = 1; | ||
| 382 | |||
| 383 | /* Otherwise they intersect and we declare them equal. | ||
| 384 | */ | ||
| 385 | } else { | ||
| 386 | result = 0; | ||
| 387 | } | ||
| 388 | |||
| 389 | return result; | ||
| 390 | } | ||
| 391 | |||
| 392 | } | ||
| 393 | } | ||