bundles/org.eclipse.ui/Eclipse JFace Text/org/eclipse/jface/text/TextSelection.java

package org.eclipse.jface.text;

/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */


/**
 * Standard implementation of <code>ITextSelection</code>.
 * Makes atvantage of the weak contract of correctness of its
 * interface. If generated from a selection provider, it only
 * remembers its offset and length and computes the remaining
 * information on request.
 */
public class TextSelection implements ITextSelection {
	
	private final static ITextSelection NULL= new TextSelection();
	
	/** Document which delivers the data of the selection */
	private IDocument fDocument;
	/** Offset of the selection */
	private int fOffset;
	/** Length of the selection */
	private int fLength;
	
	
	/**
	 * Creates an empty text selection.
	 */
	private TextSelection() {
		this(null, -1, -1);
	}
	/**
	 * Creates a text selection for the given range. This
	 * selection object describes generically a text range and
	 * is intended to be an argument for the <code>setSelection</code>
	 * method of selection providers.
	 *
	 * @param offset the offset of the range
	 * @param length the length of the range
	 */
	public TextSelection(int offset, int length) {
		this(null, offset, length);
	}
	/**
	 * Creates a text selection for the given range of the given document.
	 * This selection object is created by selection providers in responds
	 * <code>getSelection</code>.
	 *
	 * @param document the document whose text range is selected in a viewer
	 * @param offset the offset of the selected range
	 * @param length the length of the selected range
	 */ 
	public TextSelection(IDocument document, int offset, int length) {
		fDocument= document;
		fOffset= offset;
		fLength= length;
	}
	/**
	 * Returns a shared instance of an empty text selection.
	 */
	public static ITextSelection emptySelection() {
		return NULL;
	}
	/*
	 * @see ITextSelection#getEndLine
	 */
	public int getEndLine() {
		try {
			if (fDocument != null)
				return fDocument.getLineOfOffset(fOffset + fLength - 1);
		} catch (BadLocationException x) {
		}
		
		return -1;
	}
	/*
	 * @see ITextSelection#getLength
	 */
	public int getLength() {
		return fLength;
	}
	/*
	 * @see ITextSelection#getOffset
	 */
	public int getOffset() {
		return fOffset;
	}
	/*
	 * @see ITextSelection#getStartLine
	 */
	public int getStartLine() {
		
		try {
			if (fDocument != null)
				return fDocument.getLineOfOffset(fOffset);
		} catch (BadLocationException x) {
		}
		
		return -1;
	}
	/*
	 * @see ITextSelection#getText
	 */
	public String getText() {
		try {
			if (fDocument != null)
				return fDocument.get(fOffset, fLength);
		} catch (BadLocationException x) {
		}
		
		return null;
	}
	/**
	 * Returns true if the offset and length are smaller than 0. 
	 * A selection of length 0, is a valid text selection as it 
	 * describes, e.g., the cursor position in a viewer.
	 */
	/*
	 * @see ISelection#isEmpty
	 */
	public boolean isEmpty() {
		return fOffset < 0 || fLength < 0;
	}
}