GridLayer.java

/*******************************************************************************
 * Copyright (c) 2004, 2005 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.gef.editparts;

import org.eclipse.draw2d.ColorConstants;
import org.eclipse.draw2d.FigureUtilities;
import org.eclipse.draw2d.FreeformLayer;
import org.eclipse.draw2d.Graphics;
import org.eclipse.draw2d.IFigure;
import org.eclipse.draw2d.geometry.Dimension;
import org.eclipse.draw2d.geometry.Point;

import org.eclipse.gef.SnapToGrid;

/**
 * This is a layer that displays the grid.  The default grid color is {@link
 * org.eclipse.draw2d.ColorConstants#lightGray light gray}.  To change the grid color, set
 * the foreground color for this layer.
 * 
 * @author Pratik Shah
 * @since 3.0
 */
public class GridLayer 
	extends FreeformLayer 
{

/**
 * Field indicating the horizontal grid spacing
 */
protected int gridX = SnapToGrid.DEFAULT_GRID_SIZE;
/**
 * Field for the vertical grid spacing
 */
protected int gridY = SnapToGrid.DEFAULT_GRID_SIZE;

/**
 * Field indicating what the grid origin is.  This is used simply to determine the
 * offset from 0,0.
 */
protected Point origin = new Point();

/**
 * Constructor
 * Sets the default grid color: ColorConstants.lightGray
 */
public GridLayer() {
	super();
	setForegroundColor(ColorConstants.lightGray);
}

/**
 * Overridden to indicate no preferred size.  The grid layer should not affect the size of
 * the layered pane in which it is placed.
 * @see org.eclipse.draw2d.Figure#getPreferredSize(int, int)
 */
public Dimension getPreferredSize(int wHint, int hHint) {
	return new Dimension();
}

/**
 * @see org.eclipse.draw2d.Figure#paintFigure(org.eclipse.draw2d.Graphics)
 */
protected void paintFigure(Graphics graphics) {
	super.paintFigure(graphics);
	paintGrid(graphics);
}

/**
 * Paints the grid.  Sub-classes can override to customize the grid's look.  If this layer
 * is being used with SnapToGrid, this method will only be invoked when the {@link
 * SnapToGrid#PROPERTY_GRID_VISIBLE visibility} property is set to true.
 * 
 * @param	g	The Graphics object to be used to do the painting
 * @see FigureUtilities#paintGrid(Graphics, IFigure, Point, int, int)
 */
protected void paintGrid(Graphics g) {
	FigureUtilities.paintGrid(g, this, origin, gridX, gridY);
}

/**
 * Sets the origin of the grid.  The origin is used only to determine the offset from 0,0.
 * @param	p	the origin
 */
public void setOrigin(Point p) {
	if (p == null)
		p = new Point();
	if (!origin.equals(p)) {
		origin = p;
		repaint();
	}
}

/**
 * Sets the horizontal and vertical spacing of the grid.  A grid spacing of 0 will be
 * replaced with the {@link SnapToGrid#DEFAULT_GRID_SIZE default} spacing.  A negative
 * spacing will cause no grid lines to be drawn for that dimension.
 * 
 * @param	spacing		A Dimension representing the horizontal (width) and vertical 
 * 						(height) gaps
 */
public void setSpacing(Dimension spacing) {
	if (spacing == null)
		spacing = new Dimension(SnapToGrid.DEFAULT_GRID_SIZE,
					SnapToGrid.DEFAULT_GRID_SIZE);
	if (!spacing.equals(gridX, gridY)) {
		gridX = spacing.width != 0 ? spacing.width : gridX;
		gridY = spacing.height != 0 ? spacing.height : gridY;
		repaint();
	}
}

}