/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation 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:
 *     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 text viewer (
 * {@link org.eclipse.jface.text.ITextViewer}), 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>
 * <p>
 * Clients may implement this interface or use the default implementation
 * provided by {@link org.eclipse.jface.text.TextSelection}.</p>
 *
 * @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 or -1 if there is no valid text information
	 */
	int getOffset();

	/**
	 * Returns the length of the selected text.
	 *
	 * @return the length of the selected text or -1 if there is no valid text information
	 */
	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();
}