gui/org.eclipse.efm.modeling.ui.views.property.tab.xlia/src/org/eclipse/efm/papyrus/view/property/concretesyntax/sheet/tooling/UndoStyledTextManager.java

/*****************************************************************************
* Copyright (c) 2012, 2016 CEA LIST.
*
* 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:
*  Arnault Lapitre (CEA LIST) arnault.lapitre@cea.fr
*  - Initial API and implementation
*****************************************************************************/

package org.eclipse.efm.papyrus.view.property.concretesyntax.sheet.tooling;

import java.util.Stack;

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.ExtendedModifyEvent;
import org.eclipse.swt.custom.ExtendedModifyListener;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.events.KeyListener;

/**
 * Adds the Undo-Redo functionality (working Ctrl+Z and Ctrl+Y) to an instance
 * of {@link StyledText}.
 *
 * @author Petr Bodnar
 * @see {@linkplain http
 *      ://www.java2s.com/Code/Java/SWT-JFace-Eclipse/SWTUndoRedo.htm} -
 *      inspiration for this code, though not really functioning - it mainly
 *      shows which listeners to use...
 * @see {@linkplain http
 *      ://stackoverflow.com/questions/7179464/swt-how-to-recreate
 *      -a-default-context-menu-for-text-fields} -
 *      "SWT's StyledText doesn't support Undo-Redo out-of-the-box"
 */
public class UndoStyledTextManager implements KeyListener, ExtendedModifyListener {

	/**
	 * Encapsulation of the Undo and Redo stack(s).
	 */
	private static class UndoRedoStack<T> {

		private Stack<T> undo;
		private Stack<T> redo;

		public UndoRedoStack() {
			undo = new Stack<T>();
			redo = new Stack<T>();
		}

		public void pushUndo(T delta) {
			undo.add(delta);
		}

		public void pushRedo(T delta) {
			redo.add(delta);
		}

		public T popUndo() {
			T res = undo.pop();
			return res;
		}

		public T popRedo() {
			T res = redo.pop();
			return res;
		}

		public void clearRedo() {
			redo.clear();
		}

		public boolean hasUndo() {
			return !undo.isEmpty();
		}

		public boolean hasRedo() {
			return !redo.isEmpty();
		}

	}

	private StyledText editor;

	private UndoRedoStack<ExtendedModifyEvent> stack;

	private boolean isUndo;

	private boolean isRedo;

	/**
	 * Creates a new instance of this class. Automatically starts listening to
	 * corresponding key and modify events coming from the given
	 * <var>editor</var>.
	 *
	 * @param editor
	 *            the text field to which the Undo-Redo functionality should be
	 *            added
	 */
	public UndoStyledTextManager(StyledText editor) {
		editor.addExtendedModifyListener(this);
		editor.addKeyListener(this);

		this.editor = editor;
		stack = new UndoRedoStack<ExtendedModifyEvent>();
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.swt.events.KeyListener#keyPressed(org.eclipse.swt.events.
	 * KeyEvent)
	 */
	public void keyPressed(KeyEvent e) {
		// Listen to CTRL+Z for Undo, to CTRL+Y or CTRL+SHIFT+Z for Redo
		boolean isCtrl = (e.stateMask & SWT.CTRL) > 0;
		boolean isAlt = (e.stateMask & SWT.ALT) > 0;
		if (isCtrl && !isAlt) {
			boolean isShift = (e.stateMask & SWT.SHIFT) > 0;
			if (!isShift && e.keyCode == 'z') {
				undo();
			} else if (!isShift && e.keyCode == 'y' || isShift
					&& e.keyCode == 'z') {
				redo();
			}
		}
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.eclipse.swt.events.KeyListener#keyReleased(org.eclipse.swt.events
	 * .KeyEvent)
	 */
	public void keyReleased(KeyEvent e) {
		// ignore
	}

	/**
	 * Creates a corresponding Undo or Redo step from the given event and pushes
	 * it to the stack. The Redo stack is, logically, emptied if the event comes
	 * from a normal user action.
	 *
	 * @param event
	 * @see org.eclipse.swt.custom.ExtendedModifyListener#modifyText(org.eclipse.
	 *      swt.custom.ExtendedModifyEvent)
	 */
	public void modifyText(ExtendedModifyEvent event) {
		if (isUndo) {
			stack.pushRedo(event);
		} else { // is Redo or a normal user action
			stack.pushUndo(event);
			if (!isRedo) {
				stack.clearRedo();
				// TODO Switch to treat consecutive characters as one event?
			}
		}
	}

	/**
	 * Performs the Undo action. A new corresponding Redo step is automatically
	 * pushed to the stack.
	 */
	private void undo() {
		if (stack.hasUndo()) {
			isUndo = true;
			revertEvent(stack.popUndo());
			isUndo = false;
		}
	}

	/**
	 * Performs the Redo action. A new corresponding Undo step is automatically
	 * pushed to the stack.
	 */
	private void redo() {
		if (stack.hasRedo()) {
			isRedo = true;
			revertEvent(stack.popRedo());
			isRedo = false;
		}
	}

	/**
	 * Reverts the given modify event, in the way as the Eclipse text editor
	 * does it.
	 *
	 * @param event
	 */
	private void revertEvent(ExtendedModifyEvent event) {
		editor.replaceTextRange(event.start, event.length, event.replacedText);
		// (causes the modifyText() listener method to be called)

		editor.setSelectionRange(event.start, event.replacedText.length());
	}

}