1 /* 2 * Copyright (c) 2001, 2005, 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 package javax.swing; 26 27 import java.awt.Component; 28 29 /** 30 * An instance of the <code>Spring</code> class holds three properties that 31 * characterize its behavior: the <em>minimum</em>, <em>preferred</em>, and 32 * <em>maximum</em> values. Each of these properties may be involved in 33 * defining its fourth, <em>value</em>, property based on a series of rules. 34 * <p> 35 * An instance of the <code>Spring</code> class can be visualized as a 36 * mechanical spring that provides a corrective force as the spring is compressed 37 * or stretched away from its preferred value. This force is modelled 38 * as linear function of the distance from the preferred value, but with 39 * two different constants -- one for the compressional force and one for the 40 * tensional one. Those constants are specified by the minimum and maximum 41 * values of the spring such that a spring at its minimum value produces an 42 * equal and opposite force to that which is created when it is at its 43 * maximum value. The difference between the <em>preferred</em> and 44 * <em>minimum</em> values, therefore, represents the ease with which the 45 * spring can be compressed and the difference between its <em>maximum</em> 46 * and <em>preferred</em> values, indicates the ease with which the 47 * <code>Spring</code> can be extended. 48 * See the {@link #sum} method for details. 49 * 50 * <p> 51 * By defining simple arithmetic operations on <code>Spring</code>s, 52 * the behavior of a collection of <code>Spring</code>s 53 * can be reduced to that of an ordinary (non-compound) <code>Spring</code>. We define 54 * the "+", "-", <em>max</em>, and <em>min</em> operators on 55 * <code>Spring</code>s so that, in each case, the result is a <code>Spring</code> 56 * whose characteristics bear a useful mathematical relationship to its constituent 57 * springs. 58 * 59 * <p> 60 * A <code>Spring</code> can be treated as a pair of intervals 61 * with a single common point: the preferred value. 62 * The following rules define some of the 63 * arithmetic operators that can be applied to intervals 64 * (<code>[a, b]</code> refers to the interval 65 * from <code>a</code> 66 * to <code>b</code>, 67 * where <code>a <= b</code>). 68 * <p> 69 * <pre> 70 * [a1, b1] + [a2, b2] = [a1 + a2, b1 + b2] 71 * 72 * -[a, b] = [-b, -a] 73 * 74 * max([a1, b1], [a2, b2]) = [max(a1, a2), max(b1, b2)] 75 * </pre> 76 * <p> 77 * 78 * If we denote <code>Spring</code>s as <code>[a, b, c]</code>, 79 * where <code>a <= b <= c</code>, we can define the same 80 * arithmetic operators on <code>Spring</code>s: 81 * <p> 82 * <pre> 83 * [a1, b1, c1] + [a2, b2, c2] = [a1 + a2, b1 + b2, c1 + c2] 84 * 85 * -[a, b, c] = [-c, -b, -a] 86 * 87 * max([a1, b1, c1], [a2, b2, c2]) = [max(a1, a2), max(b1, b2), max(c1, c2)] 88 * </pre> 89 * <p> 90 * With both intervals and <code>Spring</code>s we can define "-" and <em>min</em> 91 * in terms of negation: 92 * <p> 93 * <pre> 94 * X - Y = X + (-Y) 95 * 96 * min(X, Y) = -max(-X, -Y) 97 * </pre> 98 * <p> 99 * For the static methods in this class that embody the arithmetic 100 * operators, we do not actually perform the operation in question as 101 * that would snapshot the values of the properties of the method's arguments 102 * at the time the static method is called. Instead, the static methods 103 * create a new <code>Spring</code> instance containing references to 104 * the method's arguments so that the characteristics of the new spring track the 105 * potentially changing characteristics of the springs from which it 106 * was made. This is a little like the idea of a <em>lazy value</em> 107 * in a functional language. 108 * <p> 109 * If you are implementing a <code>SpringLayout</code> you 110 * can find further information and examples in 111 * <a 112 href="http://java.sun.com/docs/books/tutorial/uiswing/layout/spring.html">How to Use SpringLayout</a>, 113 * a section in <em>The Java Tutorial.</em> 114 * <p> 115 * <strong>Warning:</strong> 116 * Serialized objects of this class will not be compatible with 117 * future Swing releases. The current serialization support is 118 * appropriate for short term storage or RMI between applications running 119 * the same version of Swing. As of 1.4, support for long term storage 120 * of all JavaBeans<sup><font size="-2">TM</font></sup> 121 * has been added to the <code>java.beans</code> package. 122 * Please see {@link java.beans.XMLEncoder}. 123 * 124 * @see SpringLayout 125 * @see SpringLayout.Constraints 126 * 127 * @author Philip Milne 128 * @since 1.4 129 */ 130 public abstract class Spring { 131 132 /** 133 * An integer value signifying that a property value has not yet been calculated. 134 */ 135 public static final int UNSET = Integer.MIN_VALUE; 136 137 /** 138 * Used by factory methods to create a <code>Spring</code>. 139 * 140 * @see #constant(int) 141 * @see #constant(int, int, int) 142 * @see #max 143 * @see #minus 144 * @see #sum 145 * @see SpringLayout.Constraints 146 */ 147 protected Spring() {} 148 149 /** 150 * Returns the <em>minimum</em> value of this <code>Spring</code>. 151 * 152 * @return the <code>minimumValue</code> property of this <code>Spring</code> 153 */ 154 public abstract int getMinimumValue(); 155 156 /** 157 * Returns the <em>preferred</em> value of this <code>Spring</code>. 158 * 159 * @return the <code>preferredValue</code> of this <code>Spring</code> 160 */ 161 public abstract int getPreferredValue(); 162 163 /** 164 * Returns the <em>maximum</em> value of this <code>Spring</code>. 165 * 166 * @return the <code>maximumValue</code> property of this <code>Spring</code> 167 */ 168 public abstract int getMaximumValue(); 169 170 /** 171 * Returns the current <em>value</em> of this <code>Spring</code>. 172 * 173 * @return the <code>value</code> property of this <code>Spring</code> 174 * 175 * @see #setValue 176 */ 177 public abstract int getValue(); 178 179 /** 180 * Sets the current <em>value</em> of this <code>Spring</code> to <code>value</code>. 181 * 182 * @param value the new setting of the <code>value</code> property 183 * 184 * @see #getValue 185 */ 186 public abstract void setValue(int value); 187 188 private double range(boolean contract) { 189 return contract ? (getPreferredValue() - getMinimumValue()) : 190 (getMaximumValue() - getPreferredValue()); 191 } 192 193 /*pp*/ double getStrain() { 194 double delta = (getValue() - getPreferredValue()); 195 return delta/range(getValue() < getPreferredValue()); 196 } 197 198 /*pp*/ void setStrain(double strain) { 199 setValue(getPreferredValue() + (int)(strain * range(strain < 0))); 200 } 201 202 /*pp*/ boolean isCyclic(SpringLayout l) { 203 return false; 204 } 205 206 /*pp*/ static abstract class AbstractSpring extends Spring { 207 protected int size = UNSET; 208 209 public int getValue() { 210 return size != UNSET ? size : getPreferredValue(); 211 } 212 213 public final void setValue(int size) { 214 if (this.size == size) { 215 return; 216 } 217 if (size == UNSET) { 218 clear(); 219 } else { 220 setNonClearValue(size); 221 } 222 } 223 224 protected void clear() { 225 size = UNSET; 226 } 227 228 protected void setNonClearValue(int size) { 229 this.size = size; 230 } 231 } 232 233 private static class StaticSpring extends AbstractSpring { 234 protected int min; 235 protected int pref; 236 protected int max; 237 238 public StaticSpring(int pref) { 239 this(pref, pref, pref); 240 } 241 242 public StaticSpring(int min, int pref, int max) { 243 this.min = min; 244 this.pref = pref; 245 this.max = max; 246 } 247 248 public String toString() { 249 return "StaticSpring [" + min + ", " + pref + ", " + max + "]"; 250 } 251 252 public int getMinimumValue() { 253 return min; 254 } 255 256 public int getPreferredValue() { 257 return pref; 258 } 259 260 public int getMaximumValue() { 261 return max; 262 } 263 } 264 265 private static class NegativeSpring extends Spring { 266 private Spring s; 267 268 public NegativeSpring(Spring s) { 269 this.s = s; 270 } 271 272 // Note the use of max value rather than minimum value here. 273 // See the opening preamble on arithmetic with springs. 274 275 public int getMinimumValue() { 276 return -s.getMaximumValue(); 277 } 278 279 public int getPreferredValue() { 280 return -s.getPreferredValue(); 281 } 282 283 public int getMaximumValue() { 284 return -s.getMinimumValue(); 285 } 286 287 public int getValue() { 288 return -s.getValue(); 289 } 290 291 public void setValue(int size) { 292 // No need to check for UNSET as 293 // Integer.MIN_VALUE == -Integer.MIN_VALUE. 294 s.setValue(-size); 295 } 296 297 /*pp*/ boolean isCyclic(SpringLayout l) { 298 return s.isCyclic(l); 299 } 300 } 301 302 private static class ScaleSpring extends Spring { 303 private Spring s; 304 private float factor; 305 306 private ScaleSpring(Spring s, float factor) { 307 this.s = s; 308 this.factor = factor; 309 } 310 311 public int getMinimumValue() { 312 return Math.round((factor < 0 ? s.getMaximumValue() : s.getMinimumValue()) * factor); 313 } 314 315 public int getPreferredValue() { 316 return Math.round(s.getPreferredValue() * factor); 317 } 318 319 public int getMaximumValue() { 320 return Math.round((factor < 0 ? s.getMinimumValue() : s.getMaximumValue()) * factor); 321 } 322 323 public int getValue() { 324 return Math.round(s.getValue() * factor); 325 } 326 327 public void setValue(int value) { 328 if (value == UNSET) { 329 s.setValue(UNSET); 330 } else { 331 s.setValue(Math.round(value / factor)); 332 } 333 } 334 335 /*pp*/ boolean isCyclic(SpringLayout l) { 336 return s.isCyclic(l); 337 } 338 } 339 340 /*pp*/ static class WidthSpring extends AbstractSpring { 341 /*pp*/ Component c; 342 343 public WidthSpring(Component c) { 344 this.c = c; 345 } 346 347 public int getMinimumValue() { 348 return c.getMinimumSize().width; 349 } 350 351 public int getPreferredValue() { 352 return c.getPreferredSize().width; 353 } 354 355 public int getMaximumValue() { 356 // We will be doing arithmetic with the results of this call, 357 // so if a returned value is Integer.MAX_VALUE we will get 358 // arithmetic overflow. Truncate such values. 359 return Math.min(Short.MAX_VALUE, c.getMaximumSize().width); 360 } 361 } 362 363 /*pp*/ static class HeightSpring extends AbstractSpring { 364 /*pp*/ Component c; 365 366 public HeightSpring(Component c) { 367 this.c = c; 368 } 369 370 public int getMinimumValue() { 371 return c.getMinimumSize().height; 372 } 373 374 public int getPreferredValue() { 375 return c.getPreferredSize().height; 376 } 377 378 public int getMaximumValue() { 379 return Math.min(Short.MAX_VALUE, c.getMaximumSize().height); 380 } 381 } 382 383 /*pp*/ static abstract class SpringMap extends Spring { 384 private Spring s; 385 386 public SpringMap(Spring s) { 387 this.s = s; 388 } 389 390 protected abstract int map(int i); 391 392 protected abstract int inv(int i); 393 394 public int getMinimumValue() { 395 return map(s.getMinimumValue()); 396 } 397 398 public int getPreferredValue() { 399 return map(s.getPreferredValue()); 400 } 401 402 public int getMaximumValue() { 403 return Math.min(Short.MAX_VALUE, map(s.getMaximumValue())); 404 } 405 406 public int getValue() { 407 return map(s.getValue()); 408 } 409 410 public void setValue(int value) { 411 if (value == UNSET) { 412 s.setValue(UNSET); 413 } else { 414 s.setValue(inv(value)); 415 } 416 } 417 418 /*pp*/ boolean isCyclic(SpringLayout l) { 419 return s.isCyclic(l); 420 } 421 } 422 423 // Use the instance variables of the StaticSpring superclass to 424 // cache values that have already been calculated. 425 /*pp*/ static abstract class CompoundSpring extends StaticSpring { 426 protected Spring s1; 427 protected Spring s2; 428 429 public CompoundSpring(Spring s1, Spring s2) { 430 super(UNSET); 431 this.s1 = s1; 432 this.s2 = s2; 433 } 434 435 public String toString() { 436 return "CompoundSpring of " + s1 + " and " + s2; 437 } 438 439 protected void clear() { 440 super.clear(); 441 min = pref = max = UNSET; 442 s1.setValue(UNSET); 443 s2.setValue(UNSET); 444 } 445 446 protected abstract int op(int x, int y); 447 448 public int getMinimumValue() { 449 if (min == UNSET) { 450 min = op(s1.getMinimumValue(), s2.getMinimumValue()); 451 } 452 return min; 453 } 454 455 public int getPreferredValue() { 456 if (pref == UNSET) { 457 pref = op(s1.getPreferredValue(), s2.getPreferredValue()); 458 } 459 return pref; 460 } 461 462 public int getMaximumValue() { 463 if (max == UNSET) { 464 max = op(s1.getMaximumValue(), s2.getMaximumValue()); 465 } 466 return max; 467 } 468 469 public int getValue() { 470 if (size == UNSET) { 471 size = op(s1.getValue(), s2.getValue()); 472 } 473 return size; 474 } 475 476 /*pp*/ boolean isCyclic(SpringLayout l) { 477 return l.isCyclic(s1) || l.isCyclic(s2); 478 } 479 }; 480 481 private static class SumSpring extends CompoundSpring { 482 public SumSpring(Spring s1, Spring s2) { 483 super(s1, s2); 484 } 485 486 protected int op(int x, int y) { 487 return x + y; 488 } 489 490 protected void setNonClearValue(int size) { 491 super.setNonClearValue(size); 492 s1.setStrain(this.getStrain()); 493 s2.setValue(size - s1.getValue()); 494 } 495 } 496 497 private static class MaxSpring extends CompoundSpring { 498 499 public MaxSpring(Spring s1, Spring s2) { 500 super(s1, s2); 501 } 502 503 protected int op(int x, int y) { 504 return Math.max(x, y); 505 } 506 507 protected void setNonClearValue(int size) { 508 super.setNonClearValue(size); 509 s1.setValue(size); 510 s2.setValue(size); 511 } 512 } 513 514 /** 515 * Returns a strut -- a spring whose <em>minimum</em>, <em>preferred</em>, and 516 * <em>maximum</em> values each have the value <code>pref</code>. 517 * 518 * @param pref the <em>minimum</em>, <em>preferred</em>, and 519 * <em>maximum</em> values of the new spring 520 * @return a spring whose <em>minimum</em>, <em>preferred</em>, and 521 * <em>maximum</em> values each have the value <code>pref</code> 522 * 523 * @see Spring 524 */ 525 public static Spring constant(int pref) { 526 return constant(pref, pref, pref); 527 } 528 529 /** 530 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, and 531 * <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>, 532 * and <code>max</code> respectively. 533 * 534 * @param min the <em>minimum</em> value of the new spring 535 * @param pref the <em>preferred</em> value of the new spring 536 * @param max the <em>maximum</em> value of the new spring 537 * @return a spring whose <em>minimum</em>, <em>preferred</em>, and 538 * <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>, 539 * and <code>max</code> respectively 540 * 541 * @see Spring 542 */ 543 public static Spring constant(int min, int pref, int max) { 544 return new StaticSpring(min, pref, max); 545 } 546 547 548 /** 549 * Returns <code>-s</code>: a spring running in the opposite direction to <code>s</code>. 550 * 551 * @return <code>-s</code>: a spring running in the opposite direction to <code>s</code> 552 * 553 * @see Spring 554 */ 555 public static Spring minus(Spring s) { 556 return new NegativeSpring(s); 557 } 558 559 /** 560 * Returns <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code> 561 * in series. In a sum, <code>s3</code>, of two springs, <code>s1</code> and <code>s2</code>, 562 * the <em>strains</em> of <code>s1</code>, <code>s2</code>, and <code>s3</code> are maintained 563 * at the same level (to within the precision implied by their integer <em>value</em>s). 564 * The strain of a spring in compression is: 565 * <pre> 566 * value - pref 567 * ------------ 568 * pref - min 569 * </pre> 570 * and the strain of a spring in tension is: 571 * <pre> 572 * value - pref 573 * ------------ 574 * max - pref 575 * </pre> 576 * When <code>setValue</code> is called on the sum spring, <code>s3</code>, the strain 577 * in <code>s3</code> is calculated using one of the formulas above. Once the strain of 578 * the sum is known, the <em>value</em>s of <code>s1</code> and <code>s2</code> are 579 * then set so that they are have a strain equal to that of the sum. The formulas are 580 * evaluated so as to take rounding errors into account and ensure that the sum of 581 * the <em>value</em>s of <code>s1</code> and <code>s2</code> is exactly equal to 582 * the <em>value</em> of <code>s3</code>. 583 * 584 * @return <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code> in series 585 * 586 * @see Spring 587 */ 588 public static Spring sum(Spring s1, Spring s2) { 589 return new SumSpring(s1, s2); 590 } 591 592 /** 593 * Returns <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to) 594 * the values of both <code>s1</code> and <code>s2</code>. 595 * 596 * @return <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to) 597 * the values of both <code>s1</code> and <code>s2</code> 598 * @see Spring 599 */ 600 public static Spring max(Spring s1, Spring s2) { 601 return new MaxSpring(s1, s2); 602 } 603 604 // Remove these, they're not used often and can be created using minus - 605 // as per these implementations. 606 607 /*pp*/ static Spring difference(Spring s1, Spring s2) { 608 return sum(s1, minus(s2)); 609 } 610 611 /* 612 public static Spring min(Spring s1, Spring s2) { 613 return minus(max(minus(s1), minus(s2))); 614 } 615 */ 616 617 /** 618 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em> 619 * and <em>value</em> properties are each multiples of the properties of the 620 * argument spring, <code>s</code>. Minimum and maximum properties are 621 * swapped when <code>factor</code> is negative (in accordance with the 622 * rules of interval arithmetic). 623 * <p> 624 * When factor is, for example, 0.5f the result represents 'the mid-point' 625 * of its input - an operation that is useful for centering components in 626 * a container. 627 * 628 * @param s the spring to scale 629 * @param factor amount to scale by. 630 * @return a spring whose properties are those of the input spring <code>s</code> 631 * multiplied by <code>factor</code> 632 * @throws NullPointerException if <code>s</code> is null 633 * @since 1.5 634 */ 635 public static Spring scale(Spring s, float factor) { 636 checkArg(s); 637 return new ScaleSpring(s, factor); 638 } 639 640 /** 641 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em> 642 * and <em>value</em> properties are defined by the widths of the <em>minimumSize</em>, 643 * <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties 644 * of the supplied component. The returned spring is a 'wrapper' implementation 645 * whose methods call the appropriate size methods of the supplied component. 646 * The minimum, preferred, maximum and value properties of the returned spring 647 * therefore report the current state of the appropriate properties in the 648 * component and track them as they change. 649 * 650 * @param c Component used for calculating size 651 * @return a spring whose properties are defined by the horizontal component 652 * of the component's size methods. 653 * @throws NullPointerException if <code>c</code> is null 654 * @since 1.5 655 */ 656 public static Spring width(Component c) { 657 checkArg(c); 658 return new WidthSpring(c); 659 } 660 661 /** 662 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em> 663 * and <em>value</em> properties are defined by the heights of the <em>minimumSize</em>, 664 * <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties 665 * of the supplied component. The returned spring is a 'wrapper' implementation 666 * whose methods call the appropriate size methods of the supplied component. 667 * The minimum, preferred, maximum and value properties of the returned spring 668 * therefore report the current state of the appropriate properties in the 669 * component and track them as they change. 670 * 671 * @param c Component used for calculating size 672 * @return a spring whose properties are defined by the vertical component 673 * of the component's size methods. 674 * @throws NullPointerException if <code>c</code> is null 675 * @since 1.5 676 */ 677 public static Spring height(Component c) { 678 checkArg(c); 679 return new HeightSpring(c); 680 } 681 682 683 /** 684 * If <code>s</code> is null, this throws an NullPointerException. 685 */ 686 private static void checkArg(Object s) { 687 if (s == null) { 688 throw new NullPointerException("Argument must not be null"); 689 } 690 } 691 }