Bug 184345 [Forms] ColumnLayout calculates number of columns incorrectly
In package org.eclipse.ui.forms.widgets, class ColumnLayout, method layout, I believe the number of columns is calculated incorrectly. This can cause the columns to be considerably wider than they should be. The line is: int ncolumns = (carea.width - leftMargin - rightMargin - horizontalSpacing) / (cwidth + horizontalSpacing); I think it should be: int ncolumns = (carea.width - leftMargin - rightMargin + horizontalSpacing) / (cwidth + horizontalSpacing); because the horizontalSpacing is only between columns, and not also on the outsides of the columns. (i.e. There are only ncolumns-1 horizontalSpacing's.) The derivation is: ncolumns * cwidth + (ncolumns-1) * horizontalSpacing = carea.width - leftMargin - rightMargin ==> ncolumns * cwidth + ncolumns * horizontalSpacing = carea.width - leftMargin - rightMargin + horizontalSpacing ==> ncolumns * (cwidth + horizontalSpacing) = carea.width - leftMargin - rightMargin + horizontalSpacing
bundles/org.eclipse.ui.forms/src/org/eclipse/ui/forms/widgets/ColumnLayout.java
/*******************************************************************************
 * Copyright (c) 2000, 2007 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
 *     dinko.ivanov@sap.com - patch #70790
 *******************************************************************************/
package org.eclipse.ui.forms.widgets;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;