/*******************************************************************************
 * Copyright (c) 2000, 2010 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.draw2d;

import org.eclipse.draw2d.geometry.Dimension;

/**
 * Provides generic support for LayoutManagers.
 */
public abstract class AbstractLayout implements LayoutManager {

	/**
	 * The cached preferred size.
	 */
	protected Dimension preferredSize;

	/**
	 * Whether or not this layout pays attention to visiblity of figures when
	 * calculating its bounds. By default, false.
	 */
	protected boolean isObservingVisibility = false;

	/**
	 * This method is now {@link #calculatePreferredSize(IFigure, int, int)}.
	 * 
	 * @param container
	 *            the figure
	 */
	protected final void calculatePreferredSize(IFigure container) {
	}

	/**
	 * Calculates the preferred size of the given figure, using width and height
	 * hints.
	 * 
	 * @param container
	 *            The figure
	 * @param wHint
	 *            The width hint
	 * @param hHint
	 *            The height hint
	 * @return The preferred size
	 */
	protected abstract Dimension calculatePreferredSize(IFigure container,
			int wHint, int hHint);

	/**
	 * Returns the preferred size of the figure's border.
	 * 
	 * @param container
	 *            The figure that the border is on
	 * @return The border's preferred size
	 */
	protected Dimension getBorderPreferredSize(IFigure container) {
		if (container.getBorder() == null)
			return new Dimension();
		return container.getBorder().getPreferredSize(container);
	}

	/**
	 * Returns the constraint for the given figure.
	 * 
	 * @param child
	 *            The figure
	 * @return The constraint
	 */
	public Object getConstraint(IFigure child) {
		return null;
	}

	/**
	 * This method is now {@link #getMinimumSize(IFigure, int, int)}.
	 * 
	 * @param container
	 *            the figure
	 */
	public final void getMinimumSize(IFigure container) {
	}

	/**
	 * @see org.eclipse.draw2d.LayoutManager#getMinimumSize(IFigure, int, int)
	 */
	public Dimension getMinimumSize(IFigure container, int wHint, int hHint) {
		return getPreferredSize(container, wHint, hHint);
	}

	/**
	 * Returns the preferred size of the given figure, using width and height
	 * hints. If the preferred size is cached, that size is returned. Otherwise,
	 * {@link #calculatePreferredSize(IFigure, int, int)} is called.
	 * 
	 * @param container
	 *            The figure
	 * @param wHint
	 *            The width hint
	 * @param hHint
	 *            The height hint
	 * @return The preferred size
	 */
	public Dimension getPreferredSize(IFigure container, int wHint, int hHint) {
		if (preferredSize == null)
			preferredSize = calculatePreferredSize(container, wHint, hHint);
		return preferredSize;
	}

	/**
	 * This method is now {@link #getPreferredSize(IFigure, int, int)}.
	 * 
	 * @param container
	 *            the figure
	 */
	public final void getPreferredSize(IFigure container) {
	}

	/**
	 * @see org.eclipse.draw2d.LayoutManager#invalidate()
	 */
	public void invalidate() {
		preferredSize = null;
	}

	/**
	 * Removes any cached information about the given figure.
	 * 
	 * @param child
	 *            the child that is invalidated
	 */
	protected void invalidate(IFigure child) {
		invalidate();
	}

	/**
	 * Returns whether or not this layout pays attention to visiblity when
	 * calculating its bounds.
	 * 
	 * @return true if invisible figures should not contribute to this layout's
	 *         bounds.
	 */
	public boolean isObservingVisibility() {
		return isObservingVisibility;
	}

	/**
	 * Removes the given figure from this LayoutManager's list of figures.
	 * 
	 * @param child
	 *            The figure to remove
	 */
	public void remove(IFigure child) {
		invalidate();
	}

	/**
	 * Sets the constraint for the given figure.
	 * 
	 * @param child
	 *            the child
	 * @param constraint
	 *            the child's new constraint
	 */
	public void setConstraint(IFigure child, Object constraint) {
		invalidate(child);
	}

	/**
	 * Sets isObservingVisibility to the given value.
	 * 
	 * @param newValue
	 *            <code>true</code> if visibility should be observed
	 */
	public void setObserveVisibility(boolean newValue) {
		if (isObservingVisibility == newValue)
			return;
		isObservingVisibility = newValue;
	}

}