plugins/org.eclipse.acceleo.ui.interpreter/src/org/eclipse/acceleo/ui/interpreter/internal/SWTUtil.java

/*******************************************************************************
 * Copyright (c) 2011, 2012 Obeo.
 * 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:
 *     Obeo - initial API and implementation
 *******************************************************************************/
package org.eclipse.acceleo.ui.interpreter.internal;

import org.eclipse.jface.text.source.SourceViewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.events.ControlAdapter;
import org.eclipse.swt.events.ControlEvent;
import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.events.ModifyEvent;
import org.eclipse.swt.events.ModifyListener;
import org.eclipse.swt.graphics.GC;
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.Scrollable;
import org.eclipse.swt.widgets.Text;

/**
 * This will be used by the interpreter view in order to create {@link Text} widgets that know how to hide
 * their scroll bars when they are not needed.
 * 
 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
 */
public final class SWTUtil {
	/** Utility classes don't need default constructors. */
	private SWTUtil() {
		// Hides default constructor.
	}

	/**
	 * Creates a {@link SourceViewer} widget that knows how to hide its scroll bars.
	 * 
	 * @param parent
	 *            The parent composite for this viewer.
	 * @param style
	 *            Style of the created viewer.
	 * @return The created {@link SourceViewer}.
	 */
	public static SourceViewer createScrollableSourceViewer(Composite parent, int style) {
		SourceViewer viewer = new SourceViewer(parent, null, style);

		setUpScrollableListener(viewer.getTextWidget());

		return viewer;
	}

	/**
	 * Creates a {@link StyledText} widget that knows how to hide its scroll bars.
	 * 
	 * @param parent
	 *            The parent composite for this text.
	 * @param style
	 *            Style of the created text.
	 * @return The created {@link StyledText} widget.
	 */
	public static StyledText createScrollableStyledText(Composite parent, int style) {
		final StyledText text = new StyledText(parent, style);

		// If this text has no scroll bars, simply return it.
		if ((style & (SWT.H_SCROLL | SWT.V_SCROLL)) == 0) {
			return text;
		}

		// Otherwise, set up its listeners
		setUpScrollableListener(text);

		return text;
	}

	/**
	 * Creates a {@link Text} widget that knows how to hide its scroll bars.
	 * 
	 * @param parent
	 *            The parent composite for this text.
	 * @param style
	 *            Style of the created text.
	 * @return The created {@link Text} widget.
	 */
	public static Text createScrollableText(Composite parent, int style) {
		final Text text = new Text(parent, style);

		// If this text has no scroll bars, simply return it.
		if ((style & (SWT.H_SCROLL | SWT.V_SCROLL)) == 0) {
			return text;
		}

		// Otherwise, set up its listeners
		setUpScrollableListener(text);

		return text;
	}

	/**
	 * Sets up the listeners allowing us to hide the scroll bars of the given scrollable when they are not
	 * needed.
	 * 
	 * @param scrollable
	 *            The scrollable widget to setup.
	 */
	public static void setUpScrollableListener(final Scrollable scrollable) {
		final ControlAdapter resizeListener = new ScrollableResizeListener(scrollable);
		scrollable.addControlListener(resizeListener);

		final ModifyListener modifyListener = new ScrollableModifyListener(scrollable);
		if (scrollable instanceof Text) {
			((Text)scrollable).addModifyListener(modifyListener);
		} else if (scrollable instanceof StyledText) {
			((StyledText)scrollable).addModifyListener(modifyListener);
		}

		scrollable.addDisposeListener(new DisposeListener() {
			public void widgetDisposed(DisposeEvent e) {
				scrollable.removeControlListener(resizeListener);
				if (scrollable instanceof Text) {
					((Text)scrollable).removeModifyListener(modifyListener);
				} else if (scrollable instanceof StyledText) {
					((StyledText)scrollable).removeModifyListener(modifyListener);
				}
			}
		});
	}

	/**
	 * Computes the size of the text displayed by the given {@link Text} widget.
	 * 
	 * @param widget
	 *            The widget on which is displayed the text.
	 * @param text
	 *            The actual displayed text.
	 * @return The actual size of the {@link Text} widget's content.
	 */
	protected static Point computeTextSize(Control widget, String text) {
		String[] lines = text.split("\r\n|\n|\r"); //$NON-NLS-1$

		String longestLine = ""; //$NON-NLS-1$
		if (lines.length > 0) {
			longestLine = lines[0];
			for (int i = 0; i < lines.length; i++) {
				if (lines[i].length() > longestLine.length()) {
					longestLine = lines[i];
				}
			}
		}
		GC gc = new GC(widget);
		gc.setFont(widget.getFont());
		final int textWidth = gc.stringExtent(longestLine).x;
		final int textHeight = gc.stringExtent("W").y * lines.length; //$NON-NLS-1$
		gc.dispose();

		return new Point(textWidth, textHeight);
	}

	/**
	 * This will be used as the resize listener for our scrollable text controls in order to determine whether
	 * the scroll bars are needed.
	 * 
	 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
	 */
	protected static class ScrollableModifyListener implements ModifyListener {
		/** The {@link Scrollable} widget against which this listener has been registered. */
		private final Scrollable text;

		/**
		 * Instantiates our modify listener for the given text widget.
		 * 
		 * @param text
		 *            The text widget to listen to.
		 */
		public ScrollableModifyListener(Scrollable text) {
			this.text = text;
		}

		/**
		 * {@inheritDoc}
		 * 
		 * @see org.eclipse.swt.events.ModifyListener#modifyText(org.eclipse.swt.events.ModifyEvent)
		 */
		public void modifyText(ModifyEvent e) {
			final Rectangle clientArea = text.getClientArea();
			final String currentText;
			if (text instanceof Text) {
				currentText = ((Text)text).getText();
			} else if (text instanceof StyledText) {
				currentText = ((StyledText)text).getText();
			} else {
				return;
			}
			final Point textSize = computeTextSize(text, currentText);
			if (clientArea.width > textSize.x && text.getHorizontalBar() != null) {
				text.getHorizontalBar().setVisible(false);
			} else if (text.getHorizontalBar() != null) {
				text.getHorizontalBar().setVisible(true);
			}
			if (clientArea.height > textSize.y && text.getVerticalBar() != null) {
				text.getVerticalBar().setVisible(false);
			} else if (text.getVerticalBar() != null) {
				text.getVerticalBar().setVisible(true);
			}
		}
	}

	/**
	 * This will be used as the resize listener for our scrollable text controls in order to determine whether
	 * the scroll bars are needed.
	 * 
	 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
	 */
	protected static class ScrollableResizeListener extends ControlAdapter {
		/** Keeps a reference to the last size we computed. */
		private Point lastSize;

		/** Keeps a reference to the last text we computed a size for. */
		private String lastText;

		/** The {@link Scrollable} widget against which this listener has been registered. */
		private final Scrollable text;

		/**
		 * Instantiates our resize listener for the given text widget.
		 * 
		 * @param text
		 *            The text widget to listen to.
		 */
		public ScrollableResizeListener(Scrollable text) {
			this.text = text;
		}

		/**
		 * {@inheritDoc}
		 * 
		 * @see org.eclipse.swt.events.ControlAdapter#controlResized(org.eclipse.swt.events.ControlEvent)
		 */
		@Override
		public void controlResized(ControlEvent e) {
			final Rectangle clientArea = text.getClientArea();
			final String currentText;
			if (text instanceof Text) {
				currentText = ((Text)text).getText();
			} else if (text instanceof StyledText) {
				currentText = ((StyledText)text).getText();
			} else {
				return;
			}
			Point textSize = lastSize;
			if (textSize == null || !lastText.equals(currentText)) {
				textSize = computeTextSize(text, currentText);
				lastText = currentText;
				lastSize = textSize;
			}
			if (clientArea.width > textSize.x && text.getHorizontalBar() != null) {
				if (clientArea.height > text.getHorizontalBar().getSize().y) {
					text.getHorizontalBar().setVisible(false);
				}
			} else if (text.getHorizontalBar() != null) {
				text.getHorizontalBar().setVisible(true);
			}
			if (clientArea.height > textSize.y && text.getVerticalBar() != null) {
				if (clientArea.width > text.getVerticalBar().getSize().x) {
					text.getVerticalBar().setVisible(false);
				}
			} else if (text.getVerticalBar() != null) {
				text.getVerticalBar().setVisible(true);
			}
		}
	}
}