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/*******************************************************************************
 * 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;
import org.eclipse.draw2d.geometry.Insets;
import org.eclipse.draw2d.geometry.Rectangle;

/**
 * This class handles the calculation of solving for the area of a
 * {@link org.eclipse.draw2d.ScrollPane}'s viewport and insets. Also determines
 * if the horizontal and vertical scrollbars should be visible.
 */
public class ScrollPaneSolver {

	/** Scrollbar visibility constants -- never show scrollbars **/
	public static final int NEVER = 0;
	/** Scrollbar visibility constants -- show scrollbars automatically **/
	public static final int AUTOMATIC = 1;
	/** Scrollbar visibility constants -- always show scrollbars **/
	public static final int ALWAYS = 2;

	/**
	 * Container class for the results of ScrollPaneSolver's solve method
	 */
	public static class Result {
		/** Show horizontal scrollbar boolean **/
		public boolean showH;

		/** Show vertical scrollbar boolean **/
		public boolean showV;

		/** Area of ScrollPane's viewport **/
		public Rectangle viewportArea;

		/** Insets of ScrollPane **/
		public Insets insets;
	}

	/**
	 * Solves for the viewport area, insets, and visibility of horizontal and
	 * vertical scrollbars of a ScrollPane
	 * 
	 * @param clientArea
	 *            The ScrollPane's client area
	 * @param viewport
	 *            The ScrollPane's Viewport
	 * @param hVis
	 *            Horizontal scrollbar visibility
	 * @param vVis
	 *            Vertical scrollbar visibility
	 * @param vBarWidth
	 *            Width of vertical scrollbar
	 * @param hBarHeight
	 *            Height of horizontal scrollbar
	 * @return the Result
	 */
	public static Result solve(Rectangle clientArea, Viewport viewport,
			int hVis, int vVis, int vBarWidth, int hBarHeight) {
		Result result = new Result();
		result.insets = new Insets();
		result.insets.bottom = hBarHeight;
		result.insets.right = vBarWidth;

		Dimension available = clientArea.getSize();
		Dimension guaranteed = new Dimension(available).shrink(
				(vVis == NEVER ? 0 : result.insets.right), (hVis == NEVER ? 0
						: result.insets.bottom));
		guaranteed.width = Math.max(guaranteed.width, 0);
		guaranteed.height = Math.max(guaranteed.height, 0);
		int wHint = guaranteed.width;
		int hHint = guaranteed.height;

		Dimension preferred = viewport.getPreferredSize(wHint, hHint).getCopy();
		Insets viewportInsets = viewport.getInsets();
		/*
		 * This was calling viewport.getMinimumSize(), but viewport's minimum
		 * size was really small, and wasn't a function of its contents.
		 */
		Dimension viewportMinSize = new Dimension(viewportInsets.getWidth(),
				viewportInsets.getHeight());
		if (viewport.getContents() != null) {
			if (viewport.getContentsTracksHeight() && hHint > -1)
				hHint = Math.max(0, hHint - viewportInsets.getHeight());
			if (viewport.getContentsTracksWidth() && wHint > -1)
				wHint = Math.max(0, wHint - viewportInsets.getWidth());
			viewportMinSize.expand(viewport.getContents().getMinimumSize(wHint,
					hHint));
		}

		/*
		 * Adjust preferred size if tracking flags set. Basically, tracking ==
		 * "compress view until its minimum size is reached".
		 */
		if (viewport.getContentsTracksHeight())
			preferred.height = viewportMinSize.height;
		if (viewport.getContentsTracksWidth())
			preferred.width = viewportMinSize.width;

		boolean none = available.contains(preferred), both = !none
				&& preferred.containsProper(guaranteed), showV = both
				|| preferred.height > available.height, showH = both
				|| preferred.width > available.width;

		// Adjust for visibility override flags
		result.showV = vVis != NEVER && (showV || vVis == ALWAYS);
		result.showH = hVis != NEVER && (showH || hVis == ALWAYS);

		if (!result.showV)
			result.insets.right = 0;
		if (!result.showH)
			result.insets.bottom = 0;
		result.viewportArea = clientArea.getCropped(result.insets);
		viewport.setBounds(result.viewportArea);
		return result;
	}

}