1 /* 2 * Copyright (c) 2001, 2014, 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 * 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 * 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 * 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="https://docs.oracle.com/javase/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 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 @SuppressWarnings("serial") // Same-version serialization only 131 public abstract class Spring { 132 133 /** 134 * An integer value signifying that a property value has not yet been calculated. 135 */ 136 public static final int UNSET = Integer.MIN_VALUE; 137 138 /** 139 * Used by factory methods to create a <code>Spring</code>. 140 * 141 * @see #constant(int) 142 * @see #constant(int, int, int) 143 * @see #max 144 * @see #minus 145 * @see #sum 146 * @see SpringLayout.Constraints 147 */ 148 protected Spring() {} 149 150 /** 151 * Returns the <em>minimum</em> value of this <code>Spring</code>. 152 * 153 * @return the <code>minimumValue</code> property of this <code>Spring</code> 154 */ 155 public abstract int getMinimumValue(); 156 157 /** 158 * Returns the <em>preferred</em> value of this <code>Spring</code>. 159 * 160 * @return the <code>preferredValue</code> of this <code>Spring</code> 161 */ 162 public abstract int getPreferredValue(); 163 164 /** 165 * Returns the <em>maximum</em> value of this <code>Spring</code>. 166 * 167 * @return the <code>maximumValue</code> property of this <code>Spring</code> 168 */ 169 public abstract int getMaximumValue(); 170 171 /** 172 * Returns the current <em>value</em> of this <code>Spring</code>. 173 * 174 * @return the <code>value</code> property of this <code>Spring</code> 175 * 176 * @see #setValue 177 */ 178 public abstract int getValue(); 179 180 /** 181 * Sets the current <em>value</em> of this <code>Spring</code> to <code>value</code>. 182 * 183 * @param value the new setting of the <code>value</code> property 184 * 185 * @see #getValue 186 */ 187 public abstract void setValue(int value); 188 189 private double range(boolean contract) { 190 return contract ? (getPreferredValue() - getMinimumValue()) : 191 (getMaximumValue() - getPreferredValue()); 192 } 193 194 /*pp*/ double getStrain() { 195 double delta = (getValue() - getPreferredValue()); 196 return delta/range(getValue() < getPreferredValue()); 197 } 198 199 /*pp*/ void setStrain(double strain) { 200 setValue(getPreferredValue() + (int)(strain * range(strain < 0))); 201 } 202 203 /*pp*/ boolean isCyclic(SpringLayout l) { 204 return false; 205 } 206 207 /*pp*/ static abstract class AbstractSpring extends Spring { 208 protected int size = UNSET; 209 210 public int getValue() { 211 return size != UNSET ? size : getPreferredValue(); 212 } 213 214 public final void setValue(int size) { 215 if (this.size == size) { 216 return; 217 } 218 if (size == UNSET) { 219 clear(); 220 } else { 221 setNonClearValue(size); 222 } 223 } 224 225 protected void clear() { 226 size = UNSET; 227 } 228 229 protected void setNonClearValue(int size) { 230 this.size = size; 231 } 232 } 233 234 private static class StaticSpring extends AbstractSpring { 235 protected int min; 236 protected int pref; 237 protected int max; 238 239 public StaticSpring(int pref) { 240 this(pref, pref, pref); 241 } 242 243 public StaticSpring(int min, int pref, int max) { 244 this.min = min; 245 this.pref = pref; 246 this.max = max; 247 } 248 249 public String toString() { 250 return "StaticSpring [" + min + ", " + pref + ", " + max + "]"; 251 } 252 253 public int getMinimumValue() { 254 return min; 255 } 256 257 public int getPreferredValue() { 258 return pref; 259 } 260 261 public int getMaximumValue() { 262 return max; 263 } 264 } 265 266 private static class NegativeSpring extends Spring { 267 private Spring s; 268 269 public NegativeSpring(Spring s) { 270 this.s = s; 271 } 272 273 // Note the use of max value rather than minimum value here. 274 // See the opening preamble on arithmetic with springs. 275 276 public int getMinimumValue() { 277 return -s.getMaximumValue(); 278 } 279 280 public int getPreferredValue() { 281 return -s.getPreferredValue(); 282 } 283 284 public int getMaximumValue() { 285 return -s.getMinimumValue(); 286 } 287 288 public int getValue() { 289 return -s.getValue(); 290 } 291 292 public void setValue(int size) { 293 // No need to check for UNSET as 294 // Integer.MIN_VALUE == -Integer.MIN_VALUE. 295 s.setValue(-size); 296 } 297 298 /*pp*/ boolean isCyclic(SpringLayout l) { 299 return s.isCyclic(l); 300 } 301 } 302 303 private static class ScaleSpring extends Spring { 304 private Spring s; 305 private float factor; 306 307 private ScaleSpring(Spring s, float factor) { 308 this.s = s; 309 this.factor = factor; 310 } 311 312 public int getMinimumValue() { 313 return Math.round((factor < 0 ? s.getMaximumValue() : s.getMinimumValue()) * factor); 314 } 315 316 public int getPreferredValue() { 317 return Math.round(s.getPreferredValue() * factor); 318 } 319 320 public int getMaximumValue() { 321 return Math.round((factor < 0 ? s.getMinimumValue() : s.getMaximumValue()) * factor); 322 } 323 324 public int getValue() { 325 return Math.round(s.getValue() * factor); 326 } 327 328 public void setValue(int value) { 329 if (value == UNSET) { 330 s.setValue(UNSET); 331 } else { 332 s.setValue(Math.round(value / factor)); 333 } 334 } 335 336 /*pp*/ boolean isCyclic(SpringLayout l) { 337 return s.isCyclic(l); 338 } 339 } 340 341 /*pp*/ static class WidthSpring extends AbstractSpring { 342 /*pp*/ Component c; 343 344 public WidthSpring(Component c) { 345 this.c = c; 346 } 347 348 public int getMinimumValue() { 349 return c.getMinimumSize().width; 350 } 351 352 public int getPreferredValue() { 353 return c.getPreferredSize().width; 354 } 355 356 public int getMaximumValue() { 357 // We will be doing arithmetic with the results of this call, 358 // so if a returned value is Integer.MAX_VALUE we will get 359 // arithmetic overflow. Truncate such values. 360 return Math.min(Short.MAX_VALUE, c.getMaximumSize().width); 361 } 362 } 363 364 /*pp*/ static class HeightSpring extends AbstractSpring { 365 /*pp*/ Component c; 366 367 public HeightSpring(Component c) { 368 this.c = c; 369 } 370 371 public int getMinimumValue() { 372 return c.getMinimumSize().height; 373 } 374 375 public int getPreferredValue() { 376 return c.getPreferredSize().height; 377 } 378 379 public int getMaximumValue() { 380 return Math.min(Short.MAX_VALUE, c.getMaximumSize().height); 381 } 382 } 383 384 /*pp*/ static abstract class SpringMap extends Spring { 385 private Spring s; 386 387 public SpringMap(Spring s) { 388 this.s = s; 389 } 390 391 protected abstract int map(int i); 392 393 protected abstract int inv(int i); 394 395 public int getMinimumValue() { 396 return map(s.getMinimumValue()); 397 } 398 399 public int getPreferredValue() { 400 return map(s.getPreferredValue()); 401 } 402 403 public int getMaximumValue() { 404 return Math.min(Short.MAX_VALUE, map(s.getMaximumValue())); 405 } 406 407 public int getValue() { 408 return map(s.getValue()); 409 } 410 411 public void setValue(int value) { 412 if (value == UNSET) { 413 s.setValue(UNSET); 414 } else { 415 s.setValue(inv(value)); 416 } 417 } 418 419 /*pp*/ boolean isCyclic(SpringLayout l) { 420 return s.isCyclic(l); 421 } 422 } 423 424 // Use the instance variables of the StaticSpring superclass to 425 // cache values that have already been calculated. 426 /*pp*/ static abstract class CompoundSpring extends StaticSpring { 427 protected Spring s1; 428 protected Spring s2; 429 430 public CompoundSpring(Spring s1, Spring s2) { 431 super(UNSET); 432 this.s1 = s1; 433 this.s2 = s2; 434 } 435 436 public String toString() { 437 return "CompoundSpring of " + s1 + " and " + s2; 438 } 439 440 protected void clear() { 441 super.clear(); 442 min = pref = max = UNSET; 443 s1.setValue(UNSET); 444 s2.setValue(UNSET); 445 } 446 447 protected abstract int op(int x, int y); 448 449 public int getMinimumValue() { 450 if (min == UNSET) { 451 min = op(s1.getMinimumValue(), s2.getMinimumValue()); 452 } 453 return min; 454 } 455 456 public int getPreferredValue() { 457 if (pref == UNSET) { 458 pref = op(s1.getPreferredValue(), s2.getPreferredValue()); 459 } 460 return pref; 461 } 462 463 public int getMaximumValue() { 464 if (max == UNSET) { 465 max = op(s1.getMaximumValue(), s2.getMaximumValue()); 466 } 467 return max; 468 } 469 470 public int getValue() { 471 if (size == UNSET) { 472 size = op(s1.getValue(), s2.getValue()); 473 } 474 return size; 475 } 476 477 /*pp*/ boolean isCyclic(SpringLayout l) { 478 return l.isCyclic(s1) || l.isCyclic(s2); 479 } 480 }; 481 482 private static class SumSpring extends CompoundSpring { 483 public SumSpring(Spring s1, Spring s2) { 484 super(s1, s2); 485 } 486 487 protected int op(int x, int y) { 488 return x + y; 489 } 490 491 protected void setNonClearValue(int size) { 492 super.setNonClearValue(size); 493 s1.setStrain(this.getStrain()); 494 s2.setValue(size - s1.getValue()); 495 } 496 } 497 498 private static class MaxSpring extends CompoundSpring { 499 500 public MaxSpring(Spring s1, Spring s2) { 501 super(s1, s2); 502 } 503 504 protected int op(int x, int y) { 505 return Math.max(x, y); 506 } 507 508 protected void setNonClearValue(int size) { 509 super.setNonClearValue(size); 510 s1.setValue(size); 511 s2.setValue(size); 512 } 513 } 514 515 /** 516 * Returns a strut -- a spring whose <em>minimum</em>, <em>preferred</em>, and 517 * <em>maximum</em> values each have the value <code>pref</code>. 518 * 519 * @param pref the <em>minimum</em>, <em>preferred</em>, and 520 * <em>maximum</em> values of the new spring 521 * @return a spring whose <em>minimum</em>, <em>preferred</em>, and 522 * <em>maximum</em> values each have the value <code>pref</code> 523 * 524 * @see Spring 525 */ 526 public static Spring constant(int pref) { 527 return constant(pref, pref, pref); 528 } 529 530 /** 531 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, and 532 * <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>, 533 * and <code>max</code> respectively. 534 * 535 * @param min the <em>minimum</em> value of the new spring 536 * @param pref the <em>preferred</em> value of the new spring 537 * @param max the <em>maximum</em> value of the new spring 538 * @return a spring whose <em>minimum</em>, <em>preferred</em>, and 539 * <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>, 540 * and <code>max</code> respectively 541 * 542 * @see Spring 543 */ 544 public static Spring constant(int min, int pref, int max) { 545 return new StaticSpring(min, pref, max); 546 } 547 548 549 /** 550 * Returns {@code -s}: a spring running in the opposite direction to {@code s}. 551 * 552 * @param s a {@code Spring} object 553 * @return {@code -s}: a spring running in the opposite direction to {@code s} 554 * 555 * @see Spring 556 */ 557 public static Spring minus(Spring s) { 558 return new NegativeSpring(s); 559 } 560 561 /** 562 * Returns <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code> 563 * in series. In a sum, <code>s3</code>, of two springs, <code>s1</code> and <code>s2</code>, 564 * the <em>strains</em> of <code>s1</code>, <code>s2</code>, and <code>s3</code> are maintained 565 * at the same level (to within the precision implied by their integer <em>value</em>s). 566 * The strain of a spring in compression is: 567 * <pre> 568 * value - pref 569 * ------------ 570 * pref - min 571 * </pre> 572 * and the strain of a spring in tension is: 573 * <pre> 574 * value - pref 575 * ------------ 576 * max - pref 577 * </pre> 578 * When <code>setValue</code> is called on the sum spring, <code>s3</code>, the strain 579 * in <code>s3</code> is calculated using one of the formulas above. Once the strain of 580 * the sum is known, the <em>value</em>s of <code>s1</code> and <code>s2</code> are 581 * then set so that they are have a strain equal to that of the sum. The formulas are 582 * evaluated so as to take rounding errors into account and ensure that the sum of 583 * the <em>value</em>s of <code>s1</code> and <code>s2</code> is exactly equal to 584 * the <em>value</em> of <code>s3</code>. 585 * 586 * @param s1 a {@code Spring} object 587 * @param s2 a {@code Spring} object 588 * @return <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code> in series 589 * 590 * @see Spring 591 */ 592 public static Spring sum(Spring s1, Spring s2) { 593 return new SumSpring(s1, s2); 594 } 595 596 /** 597 * Returns {@code max(s1, s2)}: a spring whose value is always greater than (or equal to) 598 * the values of both {@code s1} and {@code s2}. 599 * 600 * @param s1 a {@code Spring} object 601 * @param s2 a {@code Spring} object 602 * @return {@code max(s1, s2)}: a spring whose value is always greater than (or equal to) 603 * the values of both {@code s1} and {@code s2} 604 * @see Spring 605 */ 606 public static Spring max(Spring s1, Spring s2) { 607 return new MaxSpring(s1, s2); 608 } 609 610 // Remove these, they're not used often and can be created using minus - 611 // as per these implementations. 612 613 /*pp*/ static Spring difference(Spring s1, Spring s2) { 614 return sum(s1, minus(s2)); 615 } 616 617 /* 618 public static Spring min(Spring s1, Spring s2) { 619 return minus(max(minus(s1), minus(s2))); 620 } 621 */ 622 623 /** 624 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em> 625 * and <em>value</em> properties are each multiples of the properties of the 626 * argument spring, <code>s</code>. Minimum and maximum properties are 627 * swapped when <code>factor</code> is negative (in accordance with the 628 * rules of interval arithmetic). 629 * <p> 630 * When factor is, for example, 0.5f the result represents 'the mid-point' 631 * of its input - an operation that is useful for centering components in 632 * a container. 633 * 634 * @param s the spring to scale 635 * @param factor amount to scale by. 636 * @return a spring whose properties are those of the input spring <code>s</code> 637 * multiplied by <code>factor</code> 638 * @throws NullPointerException if <code>s</code> is null 639 * @since 1.5 640 */ 641 public static Spring scale(Spring s, float factor) { 642 checkArg(s); 643 return new ScaleSpring(s, factor); 644 } 645 646 /** 647 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em> 648 * and <em>value</em> properties are defined by the widths of the <em>minimumSize</em>, 649 * <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties 650 * of the supplied component. The returned spring is a 'wrapper' implementation 651 * whose methods call the appropriate size methods of the supplied component. 652 * The minimum, preferred, maximum and value properties of the returned spring 653 * therefore report the current state of the appropriate properties in the 654 * component and track them as they change. 655 * 656 * @param c Component used for calculating size 657 * @return a spring whose properties are defined by the horizontal component 658 * of the component's size methods. 659 * @throws NullPointerException if <code>c</code> is null 660 * @since 1.5 661 */ 662 public static Spring width(Component c) { 663 checkArg(c); 664 return new WidthSpring(c); 665 } 666 667 /** 668 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em> 669 * and <em>value</em> properties are defined by the heights of the <em>minimumSize</em>, 670 * <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties 671 * of the supplied component. The returned spring is a 'wrapper' implementation 672 * whose methods call the appropriate size methods of the supplied component. 673 * The minimum, preferred, maximum and value properties of the returned spring 674 * therefore report the current state of the appropriate properties in the 675 * component and track them as they change. 676 * 677 * @param c Component used for calculating size 678 * @return a spring whose properties are defined by the vertical component 679 * of the component's size methods. 680 * @throws NullPointerException if <code>c</code> is null 681 * @since 1.5 682 */ 683 public static Spring height(Component c) { 684 checkArg(c); 685 return new HeightSpring(c); 686 } 687 688 689 /** 690 * If <code>s</code> is null, this throws an NullPointerException. 691 */ 692 private static void checkArg(Object s) { 693 if (s == null) { 694 throw new NullPointerException("Argument must not be null"); 695 } 696 } 697 }