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Diffstat (limited to 'libjava/classpath/gnu/java/awt/AWTUtilities.java')
| -rw-r--r-- | libjava/classpath/gnu/java/awt/AWTUtilities.java | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/libjava/classpath/gnu/java/awt/AWTUtilities.java b/libjava/classpath/gnu/java/awt/AWTUtilities.java new file mode 100644 index 00000000000..a02d1c462b0 --- /dev/null +++ b/libjava/classpath/gnu/java/awt/AWTUtilities.java @@ -0,0 +1,321 @@ +/* AWTUtilities.java -- Common utility methods for AWT and Swing. + Copyright (C) 2005 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package gnu.java.awt; + +import java.awt.Component; +import java.awt.Container; +import java.util.AbstractSequentialList; +import java.util.List; +import java.util.ListIterator; +import java.util.NoSuchElementException; +import java.util.WeakHashMap; + +/** + * This class provides utility methods that are commonly used in AWT + * (and Swing). + */ +public class AWTUtilities +{ + + /** + * This List implementation wraps the Component[] returned by + * {@link Container#getComponents()} and iterates over the visible Components + * in that array. This class is used in {@link #getVisibleChildren}. + */ + static class VisibleComponentList extends AbstractSequentialList + { + /** + * The ListIterator for this List. + */ + class VisibleComponentIterator implements ListIterator + { + /** The current index in the Component[]. */ + int index; + + /** The index in the List of visible Components. */ + int listIndex; + + /** + * Creates a new VisibleComponentIterator that starts at the specified + * <code>listIndex</code>. The array of Components is searched from + * the beginning to find the matching array index. + * + * @param listIndex the index from where to begin iterating + */ + VisibleComponentIterator(int listIndex) + { + this.listIndex = listIndex; + int visibleComponentsFound = 0; + for (index = 0; visibleComponentsFound != listIndex; index++) + { + if (components[index].isVisible()) + visibleComponentsFound++; + } + } + + /** + * Returns <code>true</code> if there are more visible components in the + * array, <code>false</code> otherwise. + * + * @return <code>true</code> if there are more visible components in the + * array, <code>false</code> otherwise + */ + public boolean hasNext() + { + boolean hasNext = false; + for (int i = index; i < components.length; i++) + { + if (components[i].isVisible()) + { + hasNext = true; + break; + } + } + return hasNext; + } + + /** + * Returns the next visible <code>Component</code> in the List. + * + * @return the next visible <code>Component</code> in the List + * + * @throws if there is no next element + */ + public Object next() + { + Object o = null; + for (; index < components.length; index++) + { + if (components[index].isVisible()) + { + o = components[index]; + break; + } + } + if (o != null) + { + index++; + listIndex++; + return o; + } + else + throw new NoSuchElementException(); + } + + /** + * Returns <code>true</code> if there are more visible components in the + * array in the reverse direction, <code>false</code> otherwise. + * + * @return <code>true</code> if there are more visible components in the + * array in the reverse direction, <code>false</code> otherwise + */ + public boolean hasPrevious() + { + boolean hasPrevious = false; + for (int i = index - 1; i >= 0; i--) + { + if (components[i].isVisible()) + { + hasPrevious = true; + break; + } + } + return hasPrevious; + } + + /** + * Returns the previous visible <code>Component</code> in the List. + * + * @return the previous visible <code>Component</code> in the List + * + * @throws NoSuchElementException if there is no previous element + */ + public Object previous() + { + Object o = null; + for (index--; index >= 0; index--) + { + if (components[index].isVisible()) + { + o = components[index]; + break; + } + } + if (o != null) + { + listIndex--; + return o; + } + else + throw new NoSuchElementException(); + } + + /** + * Returns the index of the next element in the List. + * + * @return the index of the next element in the List + */ + public int nextIndex() + { + return listIndex + 1; + } + + /** + * Returns the index of the previous element in the List. + * + * @return the index of the previous element in the List + */ + public int previousIndex() + { + return listIndex - 1; + } + + /** + * This operation is not supported because the List is immutable. + * + * @throws UnsupportedOperationException because the List is immutable + */ + public void remove() + { + throw new UnsupportedOperationException + ("VisibleComponentList is immutable"); + } + + /** + * This operation is not supported because the List is immutable. + * + * @param o not used here + * + * @throws UnsupportedOperationException because the List is immutable + */ + public void set(Object o) + { + throw new UnsupportedOperationException + ("VisibleComponentList is immutable"); + } + + /** + * This operation is not supported because the List is immutable. + * + * @param o not used here + * + * @throws UnsupportedOperationException because the List is immutable + */ + public void add(Object o) + { + throw new UnsupportedOperationException + ("VisibleComponentList is immutable"); + } + } + + /** + * The components over which we iterate. Only the visible components + * are returned by this List. + */ + Component[] components; + + /** + * Creates a new instance of VisibleComponentList that wraps the specified + * <code>Component[]</code>. + * + * @param c the <code>Component[]</code> to be wrapped. + */ + VisibleComponentList(Component[] c) + { + components = c; + } + + /** + * Returns a {@link ListIterator} for iterating over this List. + * + * @return a {@link ListIterator} for iterating over this List + */ + public ListIterator listIterator(int index) + { + return new VisibleComponentIterator(index); + } + + /** + * Returns the number of visible components in the wrapped Component[]. + * + * @return the number of visible components + */ + public int size() + { + int visibleComponents = 0; + for (int i = 0; i < components.length; i++) + if (components[i].isVisible()) + visibleComponents++; + return visibleComponents; + } + } + + /** + * The cache for our List instances. We try to hold one instance of + * VisibleComponentList for each Component[] that is requested. Note + * that we use a WeakHashMap for caching, so that the cache itself + * does not keep the array or the List from beeing garbage collected + * if no other objects hold references to it. + */ + static WeakHashMap visibleChildrenCache = new WeakHashMap(); + + /** + * Returns the visible children of a {@link Container}. This method is + * commonly needed in LayoutManagers, because they only have to layout + * the visible children of a Container. + * + * @param c the Container from which to extract the visible children + * + * @return the visible children of <code>c</code> + */ + public static List getVisibleChildren(Container c) + { + Component[] children = c.getComponents(); + Object o = visibleChildrenCache.get(children); + VisibleComponentList visibleChildren = null; + if (o == null) + { + visibleChildren = new VisibleComponentList(children); + visibleChildrenCache.put(children, visibleChildren); + } + else + visibleChildren = (VisibleComponentList) o; + + return visibleChildren; + } +} |
