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