org.eclipse.mylyn.tasks.ui/src/org/eclipse/mylyn/tasks/ui/views/ToolTipHandler.java

/*******************************************************************************
 * Copyright (c) 2004 - 2005 University Of British Columbia and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     University Of British Columbia - initial API and implementation
 *******************************************************************************/
/**
 * Copied from newsgroup, forwarded from Make Technologies
 */

package org.eclipse.mylar.tasks.ui.views;

import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.mylar.tasks.ITask;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;


public class ToolTipHandler {
   private Shell parentShell;

   private Shell tipShell;

   private Label tipLabelImage;
   private Label tipLabelText;

   private Widget tipWidget; // widget this tooltip is hovering over

   protected Point tipPosition; // the position being hovered over on the
                                   // Entire display

   protected Point widgetPosition; // the position hovered over in the Widget;

   /**
	 * Creates a new tooltip handler
	 * 
	 * @param parent
	 *            the parent Shell
	 */
	public ToolTipHandler(Shell parent) {
		final Display display = parent.getDisplay();
		this.parentShell = parent;
		tipShell = new Shell(parent, SWT.NONE);
		GridLayout gridLayout = new GridLayout();
		gridLayout.numColumns = 2;
		gridLayout.marginWidth = 2;
		gridLayout.marginHeight = 2;
		tipShell.setLayout(gridLayout);
		tipShell.setBackground(display
				.getSystemColor(SWT.COLOR_INFO_BACKGROUND));

		tipLabelImage = new Label(tipShell, SWT.NONE);
		tipLabelImage.setForeground(display
				.getSystemColor(SWT.COLOR_INFO_FOREGROUND));
		tipLabelImage.setBackground(display
				.getSystemColor(SWT.COLOR_INFO_BACKGROUND));

		GridData imageGridData = new GridData(
				GridData.HORIZONTAL_ALIGN_BEGINNING
						| GridData.VERTICAL_ALIGN_BEGINNING);
		tipLabelImage.setLayoutData(imageGridData);

		tipLabelText = new Label(tipShell, SWT.NONE);
		tipLabelText.setForeground(display
				.getSystemColor(SWT.COLOR_INFO_FOREGROUND));
		tipLabelText.setBackground(display
				.getSystemColor(SWT.COLOR_INFO_BACKGROUND));

		GridData textGridData = new GridData(GridData.FILL_HORIZONTAL
				| GridData.VERTICAL_ALIGN_CENTER);
		tipLabelText.setLayoutData(textGridData);
	}

   private ITask getTask(Object hoverObject) {
		if (hoverObject instanceof Widget) {
			Object data = ((Widget) hoverObject).getData();
			if (data != null) {
				if (data instanceof ITask) {
					return (ITask) data;
				} else if (data instanceof IAdaptable) {
					return (ITask) ((IAdaptable) data).getAdapter(ITask.class);
				}

			}
		}
		return null;
	}
   
   protected String getToolTipText(Object object) {
		ITask task = getTask(object);
		if (task != null) {
			return task.getToolTipText();
		}

		if (object instanceof Control) {
			return (String) ((Control) object).getData("TIP_TEXT");
		}
		return null;
	}

   protected Image getToolTipImage(Object object) {
		ITask projectNode = getTask(object);
		if (projectNode != null) {
			// TODO Code for determining image
		}
		if (object instanceof Control) {
			return (Image) ((Control) object).getData("TIP_IMAGE");
		}
		return null;
	}

	protected Object getToolTipHelp(Object object) {
		if (object instanceof Control) {
			return (String) ((Control) object).getData("TIP_HELPTEXT");
		}
		return null;
	}

   /**
	 * Enables customized hover help for a specified control
	 * 
	 * @control the control on which to enable hoverhelp
	 */
	public void activateHoverHelp(final Control control) {
		/*
		 * Get out of the way if we attempt to activate the control underneath
		 * the tooltip
		 */
		control.addMouseListener(new MouseAdapter() {
			
			@Override
			public void mouseDown(MouseEvent e) {
				if (tipShell.isVisible())
					tipShell.setVisible(false);
			}
		});
		/*
		 * Trap hover events to pop-up tooltip
		 */
		control.addMouseTrackListener(new MouseTrackAdapter() {
			
			@Override
			public void mouseExit(MouseEvent e) {
				if (tipShell.isVisible())
					tipShell.setVisible(false);
				tipWidget = null;
			}

			@Override
			public void mouseHover(MouseEvent event) {
				widgetPosition = new Point(event.x, event.y);
				Widget widget = event.widget;
				if (widget instanceof ToolBar) {
					ToolBar w = (ToolBar) widget;
					widget = w.getItem(widgetPosition);
				}
				if (widget instanceof Table) {
					Table w = (Table) widget;
					widget = w.getItem(widgetPosition);
				}
				if (widget instanceof Tree) {
					Tree w = (Tree) widget;
					widget = w.getItem(widgetPosition);
				}
				if (widget == null) {
					tipShell.setVisible(false);
					tipWidget = null;
					return;
				}
				if (widget == tipWidget)
					return;
				tipWidget = widget;
				tipPosition = control.toDisplay(widgetPosition);
				String text = getToolTipText(widget);
				Image image = getToolTipImage(widget);
				if (text == null) {
					return;
				}
				Control sourceControl = (Control) event.getSource();
				sourceControl.setFocus();
				tipLabelText.setText(text);
				tipLabelImage.setImage(image); // accepts null
				tipShell.pack();
				setHoverLocation(tipShell, tipPosition);
				tipShell.setVisible(true);
			}
		});
		/*
		 * Trap F1 Help to pop up a custom help box
		 */
		control.addHelpListener(new HelpListener() {
			public void helpRequested(HelpEvent event) {
				if (tipWidget == null)
					return;
				Object help = getToolTipHelp(tipWidget);
				if (help == null)
					return;
				if (help.getClass() != String.class) {
					return;
				}
				if (tipShell.isVisible()) {
					tipShell.setVisible(false);
					Shell helpShell = new Shell(parentShell, SWT.SHELL_TRIM);
					helpShell.setLayout(new FillLayout());
					Label label = new Label(helpShell, SWT.NONE);
					label.setText((String) help);
					helpShell.pack();
					setHoverLocation(helpShell, tipPosition);
					helpShell.open();
				}
			}
		});
	}

   /**
	 * Sets the location for a hovering shell
	 * 
	 * @param shell
	 *            the object that is to hover
	 * @param position
	 *            the position of a widget to hover over
	 * @return the top-left location for a hovering box
	 */
	private void setHoverLocation(Shell shell, Point position) {
		Rectangle displayBounds = shell.getDisplay().getBounds();
		Rectangle shellBounds = shell.getBounds();
		shellBounds.x = Math.max(Math.min(position.x, displayBounds.width
				- shellBounds.width), 0);
		shellBounds.y = Math.max(Math.min(position.y + 16, displayBounds.height
				- shellBounds.height), 0);
		shell.setBounds(shellBounds);
	}
}