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author Jacob Carlborg <doob@me.com> <jacob.carlborg@gmail.com>
date Sat, 09 Aug 2008 17:00:02 +0200
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1 /*******************************************************************************
2 * Copyright (c) 2000, 2005 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * IBM Corporation - initial API and implementation
10 *******************************************************************************/
11 module dwt.widgets.Layout;
12
13 import dwt.dwthelper.utils;
14
15
16 import dwt.graphics.Point;
17
18 /**
19 * A layout controls the position and size
20 * of the children of a composite widget.
21 * This class is the abstract base class for
22 * layouts.
23 *
24 * @see Composite#setLayout(Layout)
25 */
26 public abstract class Layout {
27
28 /**
29 * Computes and returns the size of the specified
30 * composite's client area according to this layout.
31 * <p>
32 * This method computes the size that the client area
33 * of the composite must be in order to position all
34 * children at their preferred size inside the
35 * composite according to the layout algorithm
36 * encoded by this layout.
37 * </p>
38 * <p>
39 * When a width or height hint is supplied, it is
40 * used to constrain the result. For example, if a
41 * width hint is provided that is less than the
42 * width of the client area, the layout may choose
43 * to wrap and increase height, clip, overlap, or
44 * otherwise constrain the children.
45 * </p>
46 *
47 * @param composite a composite widget using this layout
48 * @param wHint width (<code>DWT.DEFAULT</code> for preferred size)
49 * @param hHint height (<code>DWT.DEFAULT</code> for preferred size)
50 * @param flushCache <code>true</code> means flush cached layout values
51 * @return a point containing the computed size (width, height)
52 *
53 * @see #layout
54 * @see Control#getBorderWidth
55 * @see Control#getBounds
56 * @see Control#getSize
57 * @see Control#pack(bool)
58 * @see "computeTrim, getClientArea for controls that implement them"
59 */
60 protected abstract Point computeSize (Composite composite, int wHint, int hHint, bool flushCache);
61
62 /**
63 * Instruct the layout to flush any cached values
64 * associated with the control specified in the argument
65 * <code>control</code>.
66 *
67 * @param control a control managed by this layout
68 * @return true if the Layout has flushed all cached information associated with control
69 *
70 * @since 3.1
71 */
72 protected bool flushCache (Control control) {
73 return false;
74 }
75
76 /**
77 * Lays out the children of the specified composite
78 * according to this layout.
79 * <p>
80 * This method positions and sizes the children of a
81 * composite using the layout algorithm encoded by this
82 * layout. Children of the composite are positioned in
83 * the client area of the composite. The position of
84 * the composite is not altered by this method.
85 * </p>
86 * <p>
87 * When the flush cache hint is true, the layout is
88 * instructed to flush any cached values associated
89 * with the children. Typically, a layout will cache
90 * the preferred sizes of the children to avoid the
91 * expense of computing these values each time the
92 * widget is laid out.
93 * </p>
94 * <p>
95 * When layout is triggered explicitly by the programmer
96 * the flush cache hint is true. When layout is triggered
97 * by a resize, either caused by the programmer or by the
98 * user, the hint is false.
99 * </p>
100 *
101 * @param composite a composite widget using this layout
102 * @param flushCache <code>true</code> means flush cached layout values
103 */
104 protected abstract void layout (Composite composite, bool flushCache);
105 }