/*******************************************************************************
 * Copyright (c) 2000, 2004 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
 *******************************************************************************/
package org.eclipse.jface.text;



import org.eclipse.jface.viewers.ISelection;


/**
 * This interface represents a textual selection. A text selection is
 * a range of characters. Although a text selection is a snapshot taken
 * at a particular point in time, it must not copy the line information
 * and the selected text from the selection provider.<p>
 * If, for example, the selection provider is a source viewer, and a text 
 * selection is created for the range [5, 10], the line formation for 
 * the 5th character must not be determined and remembered at the point 
 * of creation. It can  rather be determined at the point, when 
 * <code>getStartLine</code> is called. If the source viewer range [0, 15] 
 * has been changed in the meantime between the creation of the text 
 * selection object and the invocation of <code>getStartLine</code>, the returned
 * line number may differ from the line number of the 5th character at the
 * point of creation of the text selection object.<p> The contract of this
 * interface is that weak in order to allow for efficient implementations.<p>
 * Clients may implement this interface or use the default implementation provided
 * by <code>TextSelection</code>.
 * 
 * @see org.eclipse.jface.text.TextSelection
 */
public interface ITextSelection extends ISelection {
	
	/**
	 * Returns the offset of the selected text.
	 *
	 * @return the offset of the selected text
	 */
	int getOffset();
	
	/**
	 * Returns the length of the selected text.
	 *
	 * @return the length of the selected text
	 */
	int getLength();
	
	/**
	 * Returns number of the line containing the offset of the selected text.
	 * If the underlying text has been changed between the creation of this 
	 * selection object and the call of this method, the value returned might
	 * differ from what it would have been at the point of creation.
	 *
	 * @return the start line of this selection or -1 if there is no valid line information
	 */
	int getStartLine();
	
	/**
	 * Returns the number of the line containing the last character of the selected text.
	 * If the underlying text has been changed between the creation of this 
	 * selection object and the call of this method, the value returned might
	 * differ from what it would have been at the point of creation.
	 *
	 * @return the end line of this selection or -1 if there is no valid line information
	 */
	int getEndLine();
	
	/**
	 * Returns the selected text.
	 * If the underlying text has been changed between the creation of this 
	 * selection object and the call of this method, the value returned might
	 * differ from what it would have been at the point of creation.
	 *
	 * @return the selected text or <code>null</code> if there is no valid text information
	 */
	String getText();
}