swtscrolledcomposite.java

一个基于PlaceLab的室内和室外的智能导航系统

/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

/* XXX: (Yatin) I grabbed this file from the swt.custom package because
 * older versions of swt do not come with it */
package org.placelab.util.swt;


import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Layout;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.ScrollBar;

/**
 * A ScrolledComposite provides scrollbars and will scroll its content when the user
 * uses the scrollbars.
 *
 *
 * <p>There are two ways to use the ScrolledComposite:
 * 
 * <p>
 * 1) Set the size of the control that is being scrolled and the ScrolledComposite 
 * will show scrollbars when the contained control can not be fully seen.
 * 
 * 2) The second way imitates the way a browser would work.  Set the minimum size of
 * the control and the ScrolledComposite will show scroll bars if the visible area is 
 * less than the minimum size of the control and it will expand the size of the control 
 * if the visible area is greater than the minimum size.  This requires invoking 
 * both setMinWidth(), setMinHeight() and setExpandHorizontal(), setExpandVertical().
 * 
 * <code><pre>
 * public static void main (String [] args) {
 *      Display display = new Display ();
 *      Color red = display.getSystemColor(SWT.COLOR_RED);
 *      Color blue = display.getSystemColor(SWT.COLOR_BLUE);
 *      Shell shell = new Shell (display);
 *      shell.setLayout(new FillLayout());
 * 	
 *      // set the size of the scrolled content - method 1
 *      final ScrolledComposite sc1 = new ScrolledComposite(shell, SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER);
 *      final Composite c1 = new Composite(sc1, SWT.NONE);
 *      sc1.setContent(c1);
 *      c1.setBackground(red);
 *      GridLayout layout = new GridLayout();
 *      layout.numColumns = 4;
 *      c1.setLayout(layout);
 *      Button b1 = new Button (c1, SWT.PUSH);
 *      b1.setText("first button");
 *      c1.setSize(c1.computeSize(SWT.DEFAULT, SWT.DEFAULT));
 *      
 *      // set the minimum width and height of the scrolled content - method 2
 *      final ScrolledComposite sc2 = new ScrolledComposite(shell, SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER);
 *      sc2.setExpandHorizontal(true);
 *      sc2.setExpandVertical(true);
 *      final Composite c2 = new Composite(sc2, SWT.NONE);
 *      sc2.setContent(c2);
 *      c2.setBackground(blue);
 *      layout = new GridLayout();
 *      layout.numColumns = 4;
 *      c2.setLayout(layout);
 *      Button b2 = new Button (c2, SWT.PUSH);
 *      b2.setText("first button");
 *      sc2.setMinSize(c2.computeSize(SWT.DEFAULT, SWT.DEFAULT));
 *      
 *      Button add = new Button (shell, SWT.PUSH);
 *      add.setText("add children");
 *      final int[] index = new int[]{0};
 *      add.addListener(SWT.Selection, new Listener() {
 *          public void handleEvent(Event e) {
 *              index[0]++;
 *              Button button = new Button(c1, SWT.PUSH);
 *              button.setText("button "+index[0]);
 *              // reset size of content so children can be seen - method 1
 *              c1.setSize(c1.computeSize(SWT.DEFAULT, SWT.DEFAULT));
 *              c1.layout();
 *              
 *              button = new Button(c2, SWT.PUSH);
 *              button.setText("button "+index[0]);
 *              // reset the minimum width and height so children can be seen - method 2
 *              sc2.setMinSize(c2.computeSize(SWT.DEFAULT, SWT.DEFAULT));
 *              c2.layout();
 *          }
 *      });
 * 
 *      shell.open ();
 *      while (!shell.isDisposed ()) {
 *          if (!display.readAndDispatch ()) display.sleep ();
 *      }
 *      display.dispose ();
 * }
 * </pre></code>
 *
 * <dl>
 * <dt><b>Styles:</b><dd>H_SCROLL, V_SCROLL
 * </dl>
 */
public class SwtScrolledComposite extends Composite {

	private Control content;
	private Listener contentListener;
	
	private int minHeight = 0;
	private int minWidth = 0;
	private boolean expandHorizontal = false;
	private boolean expandVertical = false;
	private boolean alwaysShowScroll = false;
	private boolean inResize = false;

/**
 * Constructs a new instance of this class given its parent
 * and a style value describing its behavior and appearance.
 * <p>
 * The style value is either one of the style constants defined in
 * class <code>SWT</code> which is applicable to instances of this
 * class, or must be built by <em>bitwise OR</em>'ing together 
 * (that is, using the <code>int</code> "|" operator) two or more
 * of those <code>SWT</code> style constants. The class description
 * lists the style constants that are applicable to the class.
 * Style bits are also inherited from superclasses.
 * </p>
 *
 * @param parent a widget which will be the parent of the new instance (cannot be null)
 * @param style the style of widget to construct
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
 * </ul>
 *
 * @see SWT#H_SCROLL
 * @see SWT#V_SCROLL
 * @see #getStyle
 */	
public SwtScrolledComposite(Composite parent, int style) {
	super(parent, checkStyle(style));
	
	ScrollBar hBar = getHorizontalBar ();
	if (hBar != null) {
		hBar.addListener (SWT.Selection, new Listener () {
			public void handleEvent (Event e) {
				hScroll();
			}
		});
	}
	
	ScrollBar vBar = getVerticalBar ();
	if (vBar != null) {
		vBar.addListener (SWT.Selection, new Listener () {
			public void handleEvent (Event e) {
				vScroll();
			}
		});
	}
	
	addListener (SWT.Resize,  new Listener () {
		public void handleEvent (Event e) {
			resize();
		}
	});
	
	contentListener = new Listener() {
		public void handleEvent(Event e) {
			if (e.type != SWT.Resize) return;
			resize();
		}
	};
}

private static int checkStyle (int style) {
	int mask = SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER | SWT.LEFT_TO_RIGHT | SWT.RIGHT_TO_LEFT;
	return style & mask;
}

public Point computeSize (int wHint, int hHint, boolean changed) {
	checkWidget ();
	/*
	* When a composite does layout without using a layout
	* manager, it must take into account the preferred size
	* of it's children when computing it's preferred size in
	* the same way that a layout manager would.  In particular,
	* when a scrolled composite hides the scroll bars and
	* places a child to fill the client area, then repeated
	* calls to compute the preferred size of the scrolled
	* composite should not keep adding in the space used by
	* the scroll bars.
	*/
	if (content == null) {
		return super.computeSize (wHint, hHint, changed);
	}
	Point size = content.computeSize (wHint, hHint, changed);
	Rectangle trim = computeTrim (0, 0, size.x, size.y);
	return new Point (trim.width, trim.height);
}

/**
 * Returns the Always Show Scrollbars flag.  True if the scrollbars are 
 * always shown even if they are not required.  False if the scrollbars are only 
 * visible when some part of the composite needs to be scrolled to be seen.
 * The H_SCROLL and V_SCROLL style bits are also required to enable scrollbars in the 
 * horizontal and vertical directions.
 * 
 * @return the Always Show Scrollbars flag value
 */
public boolean getAlwaysShowScrollBars() {
	//checkWidget();
	return alwaysShowScroll;
}

/**
 * Get the content that is being scrolled.
 * 
 * @return the control displayed in the content area
 */
public Control getContent() {
	//checkWidget();
	return content;
}

private void hScroll() {
	if (content == null) return;
	Point location = content.getLocation ();
	ScrollBar hBar = getHorizontalBar ();
	int hSelection = hBar.getSelection ();
	content.setLocation (-hSelection, location.y);
}

public void layout(boolean changed) {
	checkWidget();
	if (content == null) return;
	Rectangle contentRect = content.getBounds();
	ScrollBar hBar = getHorizontalBar ();
	ScrollBar vBar = getVerticalBar ();
	if (!alwaysShowScroll) {
		boolean hVisible = needHScroll(contentRect, false);
		boolean vVisible = needVScroll(contentRect, hVisible);
		if (!hVisible && vVisible) hVisible = needHScroll(contentRect, vVisible);
		if (hBar != null) hBar.setVisible(hVisible);
		if (vBar != null) vBar.setVisible(vVisible);
	}

	Rectangle hostRect = getClientArea();
	if (expandHorizontal) {
		contentRect.width = Math.max(minWidth, hostRect.width);	
	}
	if (expandVertical) {
		contentRect.height = Math.max(minHeight, hostRect.height);
	}

	if (hBar != null) {
		hBar.setMaximum (contentRect.width);
		hBar.setThumb (Math.min (contentRect.width, hostRect.width));
		int hPage = contentRect.width - hostRect.width;
		int hSelection = hBar.getSelection ();
		if (hSelection >= hPage) {
			if (hPage <= 0) {
				hSelection = 0;
				hBar.setSelection(0);
			}
			contentRect.x = -hSelection;
		}
	}

	if (vBar != null) {
		vBar.setMaximum (contentRect.height);
		vBar.setThumb (Math.min (contentRect.height, hostRect.height));
		int vPage = contentRect.height - hostRect.height;
		int vSelection = vBar.getSelection ();
		if (vSelection >= vPage) {
			if (vPage <= 0) {
				vSelection = 0;
				vBar.setSelection(0);
			}
			contentRect.y = -vSelection;
		}
	}
	
	content.setBounds (contentRect);
}

private boolean needHScroll(Rectangle contentRect, boolean vVisible) {
	ScrollBar hBar = getHorizontalBar();
	if (hBar == null) return false;