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 *
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20 *
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24 */
25 package javax.swing;
26
27 import java.awt.Component;
28 import java.awt.Container;
29 import java.awt.Dimension;
30 import java.awt.FontMetrics;
31 import java.awt.Insets;
32 import java.awt.LayoutManager2;
33 import java.awt.Rectangle;
34 import java.util.*;
35
36 /**
37 * A <code>SpringLayout</code> lays out the children of its associated container
38 * according to a set of constraints.
39 * See <a href="http://docs.oracle.com/javase/tutorial/uiswing/layout/spring.html">How to Use SpringLayout</a>
40 * in <em>The Java Tutorial</em> for examples of using
41 * <code>SpringLayout</code>.
42 *
43 * <p>
44 * Each constraint,
45 * represented by a <code>Spring</code> object,
46 * controls the vertical or horizontal distance
47 * between two component edges.
48 * The edges can belong to
49 * any child of the container,
50 * or to the container itself.
51 * For example,
52 * the allowable width of a component
53 * can be expressed using a constraint
54 * that controls the distance between the west (left) and east (right)
55 * edges of the component.
56 * The allowable <em>y</em> coordinates for a component
57 * can be expressed by constraining the distance between
58 * the north (top) edge of the component
59 * and the north edge of its container.
60 *
61 * <P>
62 * Every child of a <code>SpringLayout</code>-controlled container,
63 * as well as the container itself,
64 * has exactly one set of constraints
65 * associated with it.
66 * These constraints are represented by
67 * a <code>SpringLayout.Constraints</code> object.
68 * By default,
69 * <code>SpringLayout</code> creates constraints
70 * that make their associated component
71 * have the minimum, preferred, and maximum sizes
72 * returned by the component's
73 * {@link java.awt.Component#getMinimumSize},
74 * {@link java.awt.Component#getPreferredSize}, and
75 * {@link java.awt.Component#getMaximumSize}
76 * methods. The <em>x</em> and <em>y</em> positions are initially not
77 * constrained, so that until you constrain them the <code>Component</code>
78 * will be positioned at 0,0 relative to the <code>Insets</code> of the
79 * parent <code>Container</code>.
80 *
81 * <p>
82 * You can change
83 * a component's constraints in several ways.
84 * You can
85 * use one of the
86 * {@link #putConstraint putConstraint}
87 * methods
88 * to establish a spring
89 * linking the edges of two components within the same container.
90 * Or you can get the appropriate <code>SpringLayout.Constraints</code>
91 * object using
92 * {@link #getConstraints getConstraints}
93 * and then modify one or more of its springs.
94 * Or you can get the spring for a particular edge of a component
95 * using {@link #getConstraint getConstraint},
96 * and modify it.
97 * You can also associate
98 * your own <code>SpringLayout.Constraints</code> object
99 * with a component by specifying the constraints object
100 * when you add the component to its container
101 * (using
102 * {@link Container#add(Component, Object)}).
103 *
104 * <p>
105 * The <code>Spring</code> object representing each constraint
106 * has a minimum, preferred, maximum, and current value.
107 * The current value of the spring
108 * is somewhere between the minimum and maximum values,
109 * according to the formula given in the
110 * {@link Spring#sum} method description.
111 * When the minimum, preferred, and maximum values are the same,
112 * the current value is always equal to them;
113 * this inflexible spring is called a <em>strut</em>.
114 * You can create struts using the factory method
115 * {@link Spring#constant(int)}.
116 * The <code>Spring</code> class also provides factory methods
117 * for creating other kinds of springs,
118 * including springs that depend on other springs.
119 *
120 * <p>
121 * In a <code>SpringLayout</code>, the position of each edge is dependent on
122 * the position of just one other edge. If a constraint is subsequently added
123 * to create a new binding for an edge, the previous binding is discarded
124 * and the edge remains dependent on a single edge.
125 * Springs should only be attached
126 * between edges of the container and its immediate children; the behavior
127 * of the <code>SpringLayout</code> when presented with constraints linking
128 * the edges of components from different containers (either internal or
129 * external) is undefined.
130 *
131 * <h3>
132 * SpringLayout vs. Other Layout Managers
133 * </h3>
134 *
135 * <blockquote>
136 * <hr>
137 * <strong>Note:</strong>
138 * Unlike many layout managers,
139 * <code>SpringLayout</code> doesn't automatically set the location of
140 * the components it manages.
141 * If you hand-code a GUI that uses <code>SpringLayout</code>,
142 * remember to initialize component locations by constraining the west/east
143 * and north/south locations.
144 * <p>
145 * Depending on the constraints you use,
146 * you may also need to set the size of the container explicitly.
147 * <hr>
148 * </blockquote>
149 *
150 * <p>
151 * Despite the simplicity of <code>SpringLayout</code>,
152 * it can emulate the behavior of most other layout managers.
153 * For some features,
154 * such as the line breaking provided by <code>FlowLayout</code>,
155 * you'll need to
156 * create a special-purpose subclass of the <code>Spring</code> class.
157 *
158 * <p>
159 * <code>SpringLayout</code> also provides a way to solve
160 * many of the difficult layout
161 * problems that cannot be solved by nesting combinations
162 * of <code>Box</code>es. That said, <code>SpringLayout</code> honors the
163 * <code>LayoutManager2</code> contract correctly and so can be nested with
164 * other layout managers -- a technique that can be preferable to
165 * creating the constraints implied by the other layout managers.
166 * <p>
167 * The asymptotic complexity of the layout operation of a <code>SpringLayout</code>
168 * is linear in the number of constraints (and/or components).
169 * <p>
170 * <strong>Warning:</strong>
171 * Serialized objects of this class will not be compatible with
172 * future Swing releases. The current serialization support is
173 * appropriate for short term storage or RMI between applications running
174 * the same version of Swing. As of 1.4, support for long term storage
175 * of all JavaBeans™
176 * has been added to the <code>java.beans</code> package.
177 * Please see {@link java.beans.XMLEncoder}.
178 *
179 * @see Spring
180 * @see SpringLayout.Constraints
181 *
182 * @author Philip Milne
183 * @author Scott Violet
184 * @author Joe Winchester
185 * @since 1.4
186 */
187 @SuppressWarnings("serial") // Same-version serialization only
188 public class SpringLayout implements LayoutManager2 {
189 private Map<Component, Constraints> componentConstraints = new HashMap<Component, Constraints>();
190
191 private Spring cyclicReference = Spring.constant(Spring.UNSET);
192 private Set<Spring> cyclicSprings;
193 private Set<Spring> acyclicSprings;
194
195
196 /**
197 * Specifies the top edge of a component's bounding rectangle.
198 */
199 public static final String NORTH = "North";
200
201 /**
202 * Specifies the bottom edge of a component's bounding rectangle.
203 */
204 public static final String SOUTH = "South";
205
206 /**
207 * Specifies the right edge of a component's bounding rectangle.
208 */
209 public static final String EAST = "East";
210
211 /**
212 * Specifies the left edge of a component's bounding rectangle.
213 */
214 public static final String WEST = "West";
215
216 /**
217 * Specifies the horizontal center of a component's bounding rectangle.
218 *
219 * @since 1.6
220 */
221 public static final String HORIZONTAL_CENTER = "HorizontalCenter";
222
223 /**
224 * Specifies the vertical center of a component's bounding rectangle.
225 *
226 * @since 1.6
227 */
228 public static final String VERTICAL_CENTER = "VerticalCenter";
229
230 /**
231 * Specifies the baseline of a component.
232 *
233 * @since 1.6
234 */
235 public static final String BASELINE = "Baseline";
236
237 /**
238 * Specifies the width of a component's bounding rectangle.
239 *
240 * @since 1.6
241 */
242 public static final String WIDTH = "Width";
243
244 /**
245 * Specifies the height of a component's bounding rectangle.
246 *
247 * @since 1.6
248 */
249 public static final String HEIGHT = "Height";
250
251 private static String[] ALL_HORIZONTAL = {WEST, WIDTH, EAST, HORIZONTAL_CENTER};
252
253 private static String[] ALL_VERTICAL = {NORTH, HEIGHT, SOUTH, VERTICAL_CENTER, BASELINE};
254
255 /**
256 * A <code>Constraints</code> object holds the
257 * constraints that govern the way a component's size and position
258 * change in a container controlled by a <code>SpringLayout</code>.
259 * A <code>Constraints</code> object is
260 * like a <code>Rectangle</code>, in that it
261 * has <code>x</code>, <code>y</code>,
262 * <code>width</code>, and <code>height</code> properties.
263 * In the <code>Constraints</code> object, however,
264 * these properties have
265 * <code>Spring</code> values instead of integers.
266 * In addition,
267 * a <code>Constraints</code> object
268 * can be manipulated as four edges
269 * -- north, south, east, and west --
270 * using the <code>constraint</code> property.
271 *
272 * <p>
273 * The following formulas are always true
274 * for a <code>Constraints</code> object (here WEST and <code>x</code> are synonyms, as are and NORTH and <code>y</code>):
275 *
276 * <pre>
277 * EAST = WEST + WIDTH
278 * SOUTH = NORTH + HEIGHT
279 * HORIZONTAL_CENTER = WEST + WIDTH/2
280 * VERTICAL_CENTER = NORTH + HEIGHT/2
281 * ABSOLUTE_BASELINE = NORTH + RELATIVE_BASELINE*
282 * </pre>
283 * <p>
284 * For example, if you have specified the WIDTH and WEST (X) location
285 * the EAST is calculated as WEST + WIDTH. If you instead specified
286 * the WIDTH and EAST locations the WEST (X) location is then calculated
287 * as EAST - WIDTH.
288 * <p>
289 * [RELATIVE_BASELINE is a private constraint that is set automatically when
290 * the SpringLayout.Constraints(Component) constructor is called or when
291 * a constraints object is registered with a SpringLayout object.]
292 * <p>
293 * <b>Note</b>: In this document,
294 * operators represent methods
295 * in the <code>Spring</code> class.
296 * For example, "a + b" is equal to
297 * <code>Spring.sum(a, b)</code>,
298 * and "a - b" is equal to
299 * <code>Spring.sum(a, Spring.minus(b))</code>.
300 * See the
301 * {@link Spring Spring API documentation}
302 * for further details
303 * of spring arithmetic.
304 *
305 * <p>
306 *
307 * Because a <code>Constraints</code> object's properties --
308 * representing its edges, size, and location -- can all be set
309 * independently and yet are interrelated,
310 * a <code>Constraints</code> object can become <em>over-constrained</em>.
311 * For example, if the <code>WEST</code>, <code>WIDTH</code> and
312 * <code>EAST</code> edges are all set, steps must be taken to ensure that
313 * the first of the formulas above holds. To do this, the
314 * <code>Constraints</code>
315 * object throws away the <em>least recently set</em>
316 * constraint so as to make the formulas hold.
317 * @since 1.4
318 */
319 public static class Constraints {
320 private Spring x;
321 private Spring y;
322 private Spring width;
323 private Spring height;
324 private Spring east;
325 private Spring south;
326 private Spring horizontalCenter;
327 private Spring verticalCenter;
328 private Spring baseline;
329
330 private List<String> horizontalHistory = new ArrayList<String>(2);
331 private List<String> verticalHistory = new ArrayList<String>(2);
332
333 // Used for baseline calculations
334 private Component c;
335
336 /**
337 * Creates an empty <code>Constraints</code> object.
338 */
339 public Constraints() {
340 }
341
342 /**
343 * Creates a <code>Constraints</code> object with the
344 * specified values for its
345 * <code>x</code> and <code>y</code> properties.
346 * The <code>height</code> and <code>width</code> springs
347 * have <code>null</code> values.
348 *
349 * @param x the spring controlling the component's <em>x</em> value
350 * @param y the spring controlling the component's <em>y</em> value
351 */
352 public Constraints(Spring x, Spring y) {
353 setX(x);
354 setY(y);
355 }
356
357 /**
358 * Creates a <code>Constraints</code> object with the
359 * specified values for its
360 * <code>x</code>, <code>y</code>, <code>width</code>,
361 * and <code>height</code> properties.
362 * Note: If the <code>SpringLayout</code> class
363 * encounters <code>null</code> values in the
364 * <code>Constraints</code> object of a given component,
365 * it replaces them with suitable defaults.
366 *
367 * @param x the spring value for the <code>x</code> property
368 * @param y the spring value for the <code>y</code> property
369 * @param width the spring value for the <code>width</code> property
370 * @param height the spring value for the <code>height</code> property
371 */
372 public Constraints(Spring x, Spring y, Spring width, Spring height) {
373 setX(x);
374 setY(y);
375 setWidth(width);
376 setHeight(height);
377 }
378
379 /**
380 * Creates a <code>Constraints</code> object with
381 * suitable <code>x</code>, <code>y</code>, <code>width</code> and
382 * <code>height</code> springs for component, <code>c</code>.
383 * The <code>x</code> and <code>y</code> springs are constant
384 * springs initialised with the component's location at
385 * the time this method is called. The <code>width</code> and
386 * <code>height</code> springs are special springs, created by
387 * the <code>Spring.width()</code> and <code>Spring.height()</code>
388 * methods, which track the size characteristics of the component
389 * when they change.
390 *
391 * @param c the component whose characteristics will be reflected by this Constraints object
392 * @throws NullPointerException if <code>c</code> is null.
393 * @since 1.5
394 */
395 public Constraints(Component c) {
396 this.c = c;
397 setX(Spring.constant(c.getX()));
398 setY(Spring.constant(c.getY()));
399 setWidth(Spring.width(c));
400 setHeight(Spring.height(c));
401 }
402
403 private void pushConstraint(String name, Spring value, boolean horizontal) {
404 boolean valid = true;
405 List<String> history = horizontal ? horizontalHistory :
406 verticalHistory;
407 if (history.contains(name)) {
408 history.remove(name);
409 valid = false;
410 } else if (history.size() == 2 && value != null) {
411 history.remove(0);
412 valid = false;
413 }
414 if (value != null) {
415 history.add(name);
416 }
417 if (!valid) {
418 String[] all = horizontal ? ALL_HORIZONTAL : ALL_VERTICAL;
419 for (String s : all) {
420 if (!history.contains(s)) {
421 setConstraint(s, null);
422 }
423 }
424 }
425 }
426
427 private Spring sum(Spring s1, Spring s2) {
428 return (s1 == null || s2 == null) ? null : Spring.sum(s1, s2);
429 }
430
431 private Spring difference(Spring s1, Spring s2) {
432 return (s1 == null || s2 == null) ? null : Spring.difference(s1, s2);
433 }
434
435 private Spring scale(Spring s, float factor) {
436 return (s == null) ? null : Spring.scale(s, factor);
437 }
438
439 private int getBaselineFromHeight(int height) {
440 if (height < 0) {
441 // Bad Scott, Bad Scott!
442 return -c.getBaseline(c.getPreferredSize().width,
443 -height);
444 }
445 return c.getBaseline(c.getPreferredSize().width, height);
446 }
447
448 private int getHeightFromBaseLine(int baseline) {
449 Dimension prefSize = c.getPreferredSize();
450 int prefHeight = prefSize.height;
451 int prefBaseline = c.getBaseline(prefSize.width, prefHeight);
452 if (prefBaseline == baseline) {
453 // If prefBaseline < 0, then no baseline, assume preferred
454 // height.
455 // If prefBaseline == baseline, then specified baseline
456 // matches preferred baseline, return preferred height
457 return prefHeight;
458 }
459 // Valid baseline
460 switch(c.getBaselineResizeBehavior()) {
461 case CONSTANT_DESCENT:
462 return prefHeight + (baseline - prefBaseline);
463 case CENTER_OFFSET:
464 return prefHeight + 2 * (baseline - prefBaseline);
465 case CONSTANT_ASCENT:
466 // Component baseline and specified baseline will NEVER
467 // match, fall through to default
468 default: // OTHER
469 // No way to map from baseline to height.
470 }
471 return Integer.MIN_VALUE;
472 }
473
474 private Spring heightToRelativeBaseline(Spring s) {
475 return new Spring.SpringMap(s) {
476 protected int map(int i) {
477 return getBaselineFromHeight(i);
478 }
479
480 protected int inv(int i) {
481 return getHeightFromBaseLine(i);
482 }
483 };
484 }
485
486 private Spring relativeBaselineToHeight(Spring s) {
487 return new Spring.SpringMap(s) {
488 protected int map(int i) {
489 return getHeightFromBaseLine(i);
490 }
491
492 protected int inv(int i) {
493 return getBaselineFromHeight(i);
494 }
495 };
496 }
497
498 private boolean defined(List history, String s1, String s2) {
499 return history.contains(s1) && history.contains(s2);
500 }
501
502 /**
503 * Sets the <code>x</code> property,
504 * which controls the <code>x</code> value
505 * of a component's location.
506 *
507 * @param x the spring controlling the <code>x</code> value
508 * of a component's location
509 *
510 * @see #getX
511 * @see SpringLayout.Constraints
512 */
513 public void setX(Spring x) {
514 this.x = x;
515 pushConstraint(WEST, x, true);
516 }
517
518 /**
519 * Returns the value of the <code>x</code> property.
520 *
521 * @return the spring controlling the <code>x</code> value
522 * of a component's location
523 *
524 * @see #setX
525 * @see SpringLayout.Constraints
526 */
527 public Spring getX() {
528 if (x == null) {
529 if (defined(horizontalHistory, EAST, WIDTH)) {
530 x = difference(east, width);
531 } else if (defined(horizontalHistory, HORIZONTAL_CENTER, WIDTH)) {
532 x = difference(horizontalCenter, scale(width, 0.5f));
533 } else if (defined(horizontalHistory, HORIZONTAL_CENTER, EAST)) {
534 x = difference(scale(horizontalCenter, 2f), east);
535 }
536 }
537 return x;
538 }
539
540 /**
541 * Sets the <code>y</code> property,
542 * which controls the <code>y</code> value
543 * of a component's location.
544 *
545 * @param y the spring controlling the <code>y</code> value
546 * of a component's location
547 *
548 * @see #getY
549 * @see SpringLayout.Constraints
550 */
551 public void setY(Spring y) {
552 this.y = y;
553 pushConstraint(NORTH, y, false);
554 }
555
556 /**
557 * Returns the value of the <code>y</code> property.
558 *
559 * @return the spring controlling the <code>y</code> value
560 * of a component's location
561 *
562 * @see #setY
563 * @see SpringLayout.Constraints
564 */
565 public Spring getY() {
566 if (y == null) {
567 if (defined(verticalHistory, SOUTH, HEIGHT)) {
568 y = difference(south, height);
569 } else if (defined(verticalHistory, VERTICAL_CENTER, HEIGHT)) {
570 y = difference(verticalCenter, scale(height, 0.5f));
571 } else if (defined(verticalHistory, VERTICAL_CENTER, SOUTH)) {
572 y = difference(scale(verticalCenter, 2f), south);
573 } else if (defined(verticalHistory, BASELINE, HEIGHT)) {
574 y = difference(baseline, heightToRelativeBaseline(height));
575 } else if (defined(verticalHistory, BASELINE, SOUTH)) {
576 y = scale(difference(baseline, heightToRelativeBaseline(south)), 2f);
577 /*
578 } else if (defined(verticalHistory, BASELINE, VERTICAL_CENTER)) {
579 y = scale(difference(baseline, heightToRelativeBaseline(scale(verticalCenter, 2))), 1f/(1-2*0.5f));
580 */
581 }
582 }
583 return y;
584 }
585
586 /**
587 * Sets the <code>width</code> property,
588 * which controls the width of a component.
589 *
590 * @param width the spring controlling the width of this
591 * <code>Constraints</code> object
592 *
593 * @see #getWidth
594 * @see SpringLayout.Constraints
595 */
596 public void setWidth(Spring width) {
597 this.width = width;
598 pushConstraint(WIDTH, width, true);
599 }
600
601 /**
602 * Returns the value of the <code>width</code> property.
603 *
604 * @return the spring controlling the width of a component
605 *
606 * @see #setWidth
607 * @see SpringLayout.Constraints
608 */
609 public Spring getWidth() {
610 if (width == null) {
611 if (horizontalHistory.contains(EAST)) {
612 width = difference(east, getX());
613 } else if (horizontalHistory.contains(HORIZONTAL_CENTER)) {
614 width = scale(difference(horizontalCenter, getX()), 2f);
615 }
616 }
617 return width;
618 }
619
620 /**
621 * Sets the <code>height</code> property,
622 * which controls the height of a component.
623 *
624 * @param height the spring controlling the height of this <code>Constraints</code>
625 * object
626 *
627 * @see #getHeight
628 * @see SpringLayout.Constraints
629 */
630 public void setHeight(Spring height) {
631 this.height = height;
632 pushConstraint(HEIGHT, height, false);
633 }
634
635 /**
636 * Returns the value of the <code>height</code> property.
637 *
638 * @return the spring controlling the height of a component
639 *
640 * @see #setHeight
641 * @see SpringLayout.Constraints
642 */
643 public Spring getHeight() {
644 if (height == null) {
645 if (verticalHistory.contains(SOUTH)) {
646 height = difference(south, getY());
647 } else if (verticalHistory.contains(VERTICAL_CENTER)) {
648 height = scale(difference(verticalCenter, getY()), 2f);
649 } else if (verticalHistory.contains(BASELINE)) {
650 height = relativeBaselineToHeight(difference(baseline, getY()));
651 }
652 }
653 return height;
654 }
655
656 private void setEast(Spring east) {
657 this.east = east;
658 pushConstraint(EAST, east, true);
659 }
660
661 private Spring getEast() {
662 if (east == null) {
663 east = sum(getX(), getWidth());
664 }
665 return east;
666 }
667
668 private void setSouth(Spring south) {
669 this.south = south;
670 pushConstraint(SOUTH, south, false);
671 }
672
673 private Spring getSouth() {
674 if (south == null) {
675 south = sum(getY(), getHeight());
676 }
677 return south;
678 }
679
680 private Spring getHorizontalCenter() {
681 if (horizontalCenter == null) {
682 horizontalCenter = sum(getX(), scale(getWidth(), 0.5f));
683 }
684 return horizontalCenter;
685 }
686
687 private void setHorizontalCenter(Spring horizontalCenter) {
688 this.horizontalCenter = horizontalCenter;
689 pushConstraint(HORIZONTAL_CENTER, horizontalCenter, true);
690 }
691
692 private Spring getVerticalCenter() {
693 if (verticalCenter == null) {
694 verticalCenter = sum(getY(), scale(getHeight(), 0.5f));
695 }
696 return verticalCenter;
697 }
698
699 private void setVerticalCenter(Spring verticalCenter) {
700 this.verticalCenter = verticalCenter;
701 pushConstraint(VERTICAL_CENTER, verticalCenter, false);
702 }
703
704 private Spring getBaseline() {
705 if (baseline == null) {
706 baseline = sum(getY(), heightToRelativeBaseline(getHeight()));
707 }
708 return baseline;
709 }
710
711 private void setBaseline(Spring baseline) {
712 this.baseline = baseline;
713 pushConstraint(BASELINE, baseline, false);
714 }
715
716 /**
717 * Sets the spring controlling the specified edge.
718 * The edge must have one of the following values:
719 * <code>SpringLayout.NORTH</code>,
720 * <code>SpringLayout.SOUTH</code>,
721 * <code>SpringLayout.EAST</code>,
722 * <code>SpringLayout.WEST</code>,
723 * <code>SpringLayout.HORIZONTAL_CENTER</code>,
724 * <code>SpringLayout.VERTICAL_CENTER</code>,
725 * <code>SpringLayout.BASELINE</code>,
726 * <code>SpringLayout.WIDTH</code> or
727 * <code>SpringLayout.HEIGHT</code>.
728 * For any other <code>String</code> value passed as the edge,
729 * no action is taken. For a <code>null</code> edge, a
730 * <code>NullPointerException</code> is thrown.
731 * <p>
732 * <b>Note:</b> This method can affect {@code x} and {@code y} values
733 * previously set for this {@code Constraints}.
734 *
735 * @param edgeName the edge to be set
736 * @param s the spring controlling the specified edge
737 *
738 * @throws NullPointerException if <code>edgeName</code> is <code>null</code>
739 *
740 * @see #getConstraint
741 * @see #NORTH
742 * @see #SOUTH
743 * @see #EAST
744 * @see #WEST
745 * @see #HORIZONTAL_CENTER
746 * @see #VERTICAL_CENTER
747 * @see #BASELINE
748 * @see #WIDTH
749 * @see #HEIGHT
750 * @see SpringLayout.Constraints
751 */
752 public void setConstraint(String edgeName, Spring s) {
753 edgeName = edgeName.intern();
754 if (edgeName == WEST) {
755 setX(s);
756 } else if (edgeName == NORTH) {
757 setY(s);
758 } else if (edgeName == EAST) {
759 setEast(s);
760 } else if (edgeName == SOUTH) {
761 setSouth(s);
762 } else if (edgeName == HORIZONTAL_CENTER) {
763 setHorizontalCenter(s);
764 } else if (edgeName == WIDTH) {
765 setWidth(s);
766 } else if (edgeName == HEIGHT) {
767 setHeight(s);
768 } else if (edgeName == VERTICAL_CENTER) {
769 setVerticalCenter(s);
770 } else if (edgeName == BASELINE) {
771 setBaseline(s);
772 }
773 }
774
775 /**
776 * Returns the value of the specified edge, which may be
777 * a derived value, or even <code>null</code>.
778 * The edge must have one of the following values:
779 * <code>SpringLayout.NORTH</code>,
780 * <code>SpringLayout.SOUTH</code>,
781 * <code>SpringLayout.EAST</code>,
782 * <code>SpringLayout.WEST</code>,
783 * <code>SpringLayout.HORIZONTAL_CENTER</code>,
784 * <code>SpringLayout.VERTICAL_CENTER</code>,
785 * <code>SpringLayout.BASELINE</code>,
786 * <code>SpringLayout.WIDTH</code> or
787 * <code>SpringLayout.HEIGHT</code>.
788 * For any other <code>String</code> value passed as the edge,
789 * <code>null</code> will be returned. Throws
790 * <code>NullPointerException</code> for a <code>null</code> edge.
791 *
792 * @param edgeName the edge whose value
793 * is to be returned
794 *
795 * @return the spring controlling the specified edge, may be <code>null</code>
796 *
797 * @throws NullPointerException if <code>edgeName</code> is <code>null</code>
798 *
799 * @see #setConstraint
800 * @see #NORTH
801 * @see #SOUTH
802 * @see #EAST
803 * @see #WEST
804 * @see #HORIZONTAL_CENTER
805 * @see #VERTICAL_CENTER
806 * @see #BASELINE
807 * @see #WIDTH
808 * @see #HEIGHT
809 * @see SpringLayout.Constraints
810 */
811 public Spring getConstraint(String edgeName) {
812 edgeName = edgeName.intern();
813 return (edgeName == WEST) ? getX() :
814 (edgeName == NORTH) ? getY() :
815 (edgeName == EAST) ? getEast() :
816 (edgeName == SOUTH) ? getSouth() :
817 (edgeName == WIDTH) ? getWidth() :
818 (edgeName == HEIGHT) ? getHeight() :
819 (edgeName == HORIZONTAL_CENTER) ? getHorizontalCenter() :
820 (edgeName == VERTICAL_CENTER) ? getVerticalCenter() :
821 (edgeName == BASELINE) ? getBaseline() :
822 null;
823 }
824
825 /*pp*/ void reset() {
826 Spring[] allSprings = {x, y, width, height, east, south,
827 horizontalCenter, verticalCenter, baseline};
828 for (Spring s : allSprings) {
829 if (s != null) {
830 s.setValue(Spring.UNSET);
831 }
832 }
833 }
834 }
835
836 private static class SpringProxy extends Spring {
837 private String edgeName;
838 private Component c;
839 private SpringLayout l;
840
841 public SpringProxy(String edgeName, Component c, SpringLayout l) {
842 this.edgeName = edgeName;
843 this.c = c;
844 this.l = l;
845 }
846
847 private Spring getConstraint() {
848 return l.getConstraints(c).getConstraint(edgeName);
849 }
850
851 public int getMinimumValue() {
852 return getConstraint().getMinimumValue();
853 }
854
855 public int getPreferredValue() {
856 return getConstraint().getPreferredValue();
857 }
858
859 public int getMaximumValue() {
860 return getConstraint().getMaximumValue();
861 }
862
863 public int getValue() {
864 return getConstraint().getValue();
865 }
866
867 public void setValue(int size) {
868 getConstraint().setValue(size);
869 }
870
871 /*pp*/ boolean isCyclic(SpringLayout l) {
872 return l.isCyclic(getConstraint());
873 }
874
875 public String toString() {
876 return "SpringProxy for " + edgeName + " edge of " + c.getName() + ".";
877 }
878 }
879
880 /**
881 * Constructs a new <code>SpringLayout</code>.
882 */
883 public SpringLayout() {}
884
885 private void resetCyclicStatuses() {
886 cyclicSprings = new HashSet<Spring>();
887 acyclicSprings = new HashSet<Spring>();
888 }
889
890 private void setParent(Container p) {
891 resetCyclicStatuses();
892 Constraints pc = getConstraints(p);
893
894 pc.setX(Spring.constant(0));
895 pc.setY(Spring.constant(0));
896 // The applyDefaults() method automatically adds width and
897 // height springs that delegate their calculations to the
898 // getMinimumSize(), getPreferredSize() and getMaximumSize()
899 // methods of the relevant component. In the case of the
900 // parent this will cause an infinite loop since these
901 // methods, in turn, delegate their calculations to the
902 // layout manager. Check for this case and replace the
903 // the springs that would cause this problem with a
904 // constant springs that supply default values.
905 Spring width = pc.getWidth();
906 if (width instanceof Spring.WidthSpring && ((Spring.WidthSpring)width).c == p) {
907 pc.setWidth(Spring.constant(0, 0, Integer.MAX_VALUE));
908 }
909 Spring height = pc.getHeight();
910 if (height instanceof Spring.HeightSpring && ((Spring.HeightSpring)height).c == p) {
911 pc.setHeight(Spring.constant(0, 0, Integer.MAX_VALUE));
912 }
913 }
914
915 /*pp*/ boolean isCyclic(Spring s) {
916 if (s == null) {
917 return false;
918 }
919 if (cyclicSprings.contains(s)) {
920 return true;
921 }
922 if (acyclicSprings.contains(s)) {
923 return false;
924 }
925 cyclicSprings.add(s);
926 boolean result = s.isCyclic(this);
927 if (!result) {
928 acyclicSprings.add(s);
929 cyclicSprings.remove(s);
930 }
931 else {
932 System.err.println(s + " is cyclic. ");
933 }
934 return result;
935 }
936
937 private Spring abandonCycles(Spring s) {
938 return isCyclic(s) ? cyclicReference : s;
939 }
940
941 // LayoutManager methods.
942
943 /**
944 * Has no effect,
945 * since this layout manager does not
946 * use a per-component string.
947 */
948 public void addLayoutComponent(String name, Component c) {}
949
950 /**
951 * Removes the constraints associated with the specified component.
952 *
953 * @param c the component being removed from the container
954 */
955 public void removeLayoutComponent(Component c) {
956 componentConstraints.remove(c);
957 }
958
959 private static Dimension addInsets(int width, int height, Container p) {
960 Insets i = p.getInsets();
961 return new Dimension(width + i.left + i.right, height + i.top + i.bottom);
962 }
963
964 public Dimension minimumLayoutSize(Container parent) {
965 setParent(parent);
966 Constraints pc = getConstraints(parent);
967 return addInsets(abandonCycles(pc.getWidth()).getMinimumValue(),
968 abandonCycles(pc.getHeight()).getMinimumValue(),
969 parent);
970 }
971
972 public Dimension preferredLayoutSize(Container parent) {
973 setParent(parent);
974 Constraints pc = getConstraints(parent);
975 return addInsets(abandonCycles(pc.getWidth()).getPreferredValue(),
976 abandonCycles(pc.getHeight()).getPreferredValue(),
977 parent);
978 }
979
980 // LayoutManager2 methods.
981
982 public Dimension maximumLayoutSize(Container parent) {
983 setParent(parent);
984 Constraints pc = getConstraints(parent);
985 return addInsets(abandonCycles(pc.getWidth()).getMaximumValue(),
986 abandonCycles(pc.getHeight()).getMaximumValue(),
987 parent);
988 }
989
990 /**
991 * If <code>constraints</code> is an instance of
992 * <code>SpringLayout.Constraints</code>,
993 * associates the constraints with the specified component.
994 *
995 * @param component the component being added
996 * @param constraints the component's constraints
997 *
998 * @see SpringLayout.Constraints
999 */
1000 public void addLayoutComponent(Component component, Object constraints) {
1001 if (constraints instanceof Constraints) {
1002 putConstraints(component, (Constraints)constraints);
1003 }
1004 }
1005
1006 /**
1007 * Returns 0.5f (centered).
1008 */
1009 public float getLayoutAlignmentX(Container p) {
1010 return 0.5f;
1011 }
1012
1013 /**
1014 * Returns 0.5f (centered).
1015 */
1016 public float getLayoutAlignmentY(Container p) {
1017 return 0.5f;
1018 }
1019
1020 public void invalidateLayout(Container p) {}
1021
1022 // End of LayoutManger2 methods
1023
1024 /**
1025 * Links edge <code>e1</code> of component <code>c1</code> to
1026 * edge <code>e2</code> of component <code>c2</code>,
1027 * with a fixed distance between the edges. This
1028 * constraint will cause the assignment
1029 * <pre>
1030 * value(e1, c1) = value(e2, c2) + pad</pre>
1031 * to take place during all subsequent layout operations.
1032 *
1033 * @param e1 the edge of the dependent
1034 * @param c1 the component of the dependent
1035 * @param pad the fixed distance between dependent and anchor
1036 * @param e2 the edge of the anchor
1037 * @param c2 the component of the anchor
1038 *
1039 * @see #putConstraint(String, Component, Spring, String, Component)
1040 */
1041 public void putConstraint(String e1, Component c1, int pad, String e2, Component c2) {
1042 putConstraint(e1, c1, Spring.constant(pad), e2, c2);
1043 }
1044
1045 /**
1046 * Links edge <code>e1</code> of component <code>c1</code> to
1047 * edge <code>e2</code> of component <code>c2</code>. As edge
1048 * <code>(e2, c2)</code> changes value, edge <code>(e1, c1)</code> will
1049 * be calculated by taking the (spring) sum of <code>(e2, c2)</code>
1050 * and <code>s</code>.
1051 * Each edge must have one of the following values:
1052 * <code>SpringLayout.NORTH</code>,
1053 * <code>SpringLayout.SOUTH</code>,
1054 * <code>SpringLayout.EAST</code>,
1055 * <code>SpringLayout.WEST</code>,
1056 * <code>SpringLayout.VERTICAL_CENTER</code>,
1057 * <code>SpringLayout.HORIZONTAL_CENTER</code> or
1058 * <code>SpringLayout.BASELINE</code>.
1059 *
1060 * @param e1 the edge of the dependent
1061 * @param c1 the component of the dependent
1062 * @param s the spring linking dependent and anchor
1063 * @param e2 the edge of the anchor
1064 * @param c2 the component of the anchor
1065 *
1066 * @see #putConstraint(String, Component, int, String, Component)
1067 * @see #NORTH
1068 * @see #SOUTH
1069 * @see #EAST
1070 * @see #WEST
1071 * @see #VERTICAL_CENTER
1072 * @see #HORIZONTAL_CENTER
1073 * @see #BASELINE
1074 */
1075 public void putConstraint(String e1, Component c1, Spring s, String e2, Component c2) {
1076 putConstraint(e1, c1, Spring.sum(s, getConstraint(e2, c2)));
1077 }
1078
1079 private void putConstraint(String e, Component c, Spring s) {
1080 if (s != null) {
1081 getConstraints(c).setConstraint(e, s);
1082 }
1083 }
1084
1085 private Constraints applyDefaults(Component c, Constraints constraints) {
1086 if (constraints == null) {
1087 constraints = new Constraints();
1088 }
1089 if (constraints.c == null) {
1090 constraints.c = c;
1091 }
1092 if (constraints.horizontalHistory.size() < 2) {
1093 applyDefaults(constraints, WEST, Spring.constant(0), WIDTH,
1094 Spring.width(c), constraints.horizontalHistory);
1095 }
1096 if (constraints.verticalHistory.size() < 2) {
1097 applyDefaults(constraints, NORTH, Spring.constant(0), HEIGHT,
1098 Spring.height(c), constraints.verticalHistory);
1099 }
1100 return constraints;
1101 }
1102
1103 private void applyDefaults(Constraints constraints, String name1,
1104 Spring spring1, String name2, Spring spring2,
1105 List<String> history) {
1106 if (history.size() == 0) {
1107 constraints.setConstraint(name1, spring1);
1108 constraints.setConstraint(name2, spring2);
1109 } else {
1110 // At this point there must be exactly one constraint defined already.
1111 // Check width/height first.
1112 if (constraints.getConstraint(name2) == null) {
1113 constraints.setConstraint(name2, spring2);
1114 } else {
1115 // If width/height is already defined, install a default for x/y.
1116 constraints.setConstraint(name1, spring1);
1117 }
1118 // Either way, leave the user's constraint topmost on the stack.
1119 Collections.rotate(history, 1);
1120 }
1121 }
1122
1123 private void putConstraints(Component component, Constraints constraints) {
1124 componentConstraints.put(component, applyDefaults(component, constraints));
1125 }
1126
1127 /**
1128 * Returns the constraints for the specified component.
1129 * Note that,
1130 * unlike the <code>GridBagLayout</code>
1131 * <code>getConstraints</code> method,
1132 * this method does not clone constraints.
1133 * If no constraints
1134 * have been associated with this component,
1135 * this method
1136 * returns a default constraints object positioned at
1137 * 0,0 relative to the parent's Insets and its width/height
1138 * constrained to the minimum, maximum, and preferred sizes of the
1139 * component. The size characteristics
1140 * are not frozen at the time this method is called;
1141 * instead this method returns a constraints object
1142 * whose characteristics track the characteristics
1143 * of the component as they change.
1144 *
1145 * @param c the component whose constraints will be returned
1146 *
1147 * @return the constraints for the specified component
1148 */
1149 public Constraints getConstraints(Component c) {
1150 Constraints result = componentConstraints.get(c);
1151 if (result == null) {
1152 if (c instanceof javax.swing.JComponent) {
1153 Object cp = ((javax.swing.JComponent)c).getClientProperty(SpringLayout.class);
1154 if (cp instanceof Constraints) {
1155 return applyDefaults(c, (Constraints)cp);
1156 }
1157 }
1158 result = new Constraints();
1159 putConstraints(c, result);
1160 }
1161 return result;
1162 }
1163
1164 /**
1165 * Returns the spring controlling the distance between
1166 * the specified edge of
1167 * the component and the top or left edge of its parent. This
1168 * method, instead of returning the current binding for the
1169 * edge, returns a proxy that tracks the characteristics
1170 * of the edge even if the edge is subsequently rebound.
1171 * Proxies are intended to be used in builder environments
1172 * where it is useful to allow the user to define the
1173 * constraints for a layout in any order. Proxies do, however,
1174 * provide the means to create cyclic dependencies amongst
1175 * the constraints of a layout. Such cycles are detected
1176 * internally by <code>SpringLayout</code> so that
1177 * the layout operation always terminates.
1178 *
1179 * @param edgeName must be one of
1180 * <code>SpringLayout.NORTH</code>,
1181 * <code>SpringLayout.SOUTH</code>,
1182 * <code>SpringLayout.EAST</code>,
1183 * <code>SpringLayout.WEST</code>,
1184 * <code>SpringLayout.VERTICAL_CENTER</code>,
1185 * <code>SpringLayout.HORIZONTAL_CENTER</code> or
1186 * <code>SpringLayout.BASELINE</code>
1187 * @param c the component whose edge spring is desired
1188 *
1189 * @return a proxy for the spring controlling the distance between the
1190 * specified edge and the top or left edge of its parent
1191 *
1192 * @see #NORTH
1193 * @see #SOUTH
1194 * @see #EAST
1195 * @see #WEST
1196 * @see #VERTICAL_CENTER
1197 * @see #HORIZONTAL_CENTER
1198 * @see #BASELINE
1199 */
1200 public Spring getConstraint(String edgeName, Component c) {
1201 // The interning here is unnecessary; it was added for efficiency.
1202 edgeName = edgeName.intern();
1203 return new SpringProxy(edgeName, c, this);
1204 }
1205
1206 public void layoutContainer(Container parent) {
1207 setParent(parent);
1208
1209 int n = parent.getComponentCount();
1210 getConstraints(parent).reset();
1211 for (int i = 0 ; i < n ; i++) {
1212 getConstraints(parent.getComponent(i)).reset();
1213 }
1214
1215 Insets insets = parent.getInsets();
1216 Constraints pc = getConstraints(parent);
1217 abandonCycles(pc.getX()).setValue(0);
1218 abandonCycles(pc.getY()).setValue(0);
1219 abandonCycles(pc.getWidth()).setValue(parent.getWidth() -
1220 insets.left - insets.right);
1221 abandonCycles(pc.getHeight()).setValue(parent.getHeight() -
1222 insets.top - insets.bottom);
1223
1224 for (int i = 0 ; i < n ; i++) {
1225 Component c = parent.getComponent(i);
1226 Constraints cc = getConstraints(c);
1227 int x = abandonCycles(cc.getX()).getValue();
1228 int y = abandonCycles(cc.getY()).getValue();
1229 int width = abandonCycles(cc.getWidth()).getValue();
1230 int height = abandonCycles(cc.getHeight()).getValue();
1231 c.setBounds(insets.left + x, insets.top + y, width, height);
1232 }
1233 }
1234 }