Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2018 IBM Corporation and others. * * This program and the accompanying materials * are made available under the terms of the Eclipse Public License 2.0 * which accompanies this distribution, and is available at * https://www.eclipse.org/legal/epl-2.0/ * * SPDX-License-Identifier: EPL-2.0 * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.swt.layout; import org.eclipse.swt.*; import org.eclipse.swt.graphics.*; import org.eclipse.swt.widgets.*; /** * <code>FillLayout</code> is the simplest layout class. It lays out * controls in a single row or column, forcing them to be the same size. * <p> * Initially, the controls will all be as tall as the tallest control, * and as wide as the widest. <code>FillLayout</code> does not wrap, * but you can specify margins and spacing. You might use it to * lay out buttons in a task bar or tool bar, or to stack checkboxes * in a <code>Group</code>. <code>FillLayout</code> can also be used * when a <code>Composite</code> only has one child. For example, * if a <code>Shell</code> has a single <code>Group</code> child, * <code>FillLayout</code> will cause the <code>Group</code> to * completely fill the <code>Shell</code> (if margins are 0). * </p> * <p> * Example code: first a <code>FillLayout</code> is created and * its type field is set, and then the layout is set into the * <code>Composite</code>. Note that in a <code>FillLayout</code>, * children are always the same size, and they fill all available space. * </p> * <pre> * FillLayout fillLayout = new FillLayout(); * fillLayout.type = SWT.VERTICAL; * shell.setLayout(fillLayout); * </pre> * * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: LayoutExample</a> * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a> */ public final class FillLayout extends Layout { /** * type specifies how controls will be positioned * within the layout. * * The default value is HORIZONTAL. * * Possible values are: <ul> * <li>HORIZONTAL: Position the controls horizontally from left to right</li> * <li>VERTICAL: Position the controls vertically from top to bottom</li> * </ul> */ public int type = SWT.HORIZONTAL; /** * marginWidth specifies the number of points of horizontal margin * that will be placed along the left and right edges of the layout. * * The default value is 0. * * @since 3.0 */ public int marginWidth = 0; /** * marginHeight specifies the number of points of vertical margin * that will be placed along the top and bottom edges of the layout. * * The default value is 0. * * @since 3.0 */ public int marginHeight = 0; /** * spacing specifies the number of points between the edge of one cell * and the edge of its neighbouring cell. * * The default value is 0. * * @since 3.0 */ public int spacing = 0; /** * Constructs a new instance of this class. */ public FillLayout() { } /** * Constructs a new instance of this class given the type. * * @param type the type of fill layout * * @since 2.0 */ public FillLayout(int type) { this.type = type; } @Override protected Point computeSize(Composite composite, int wHint, int hHint, boolean flushCache) { Control[] children = composite.getChildren(); int count = children.length; int maxWidth = 0, maxHeight = 0; for (int i = 0; i < count; i++) { Control child = children[i]; int w = wHint, h = hHint; if (count > 0) { if (type == SWT.HORIZONTAL && wHint != SWT.DEFAULT) { w = Math.max(0, (wHint - (count - 1) * spacing) / count); } if (type == SWT.VERTICAL && hHint != SWT.DEFAULT) { h = Math.max(0, (hHint - (count - 1) * spacing) / count); } } Point size = computeChildSize(child, w, h, flushCache); maxWidth = Math.max(maxWidth, size.x); maxHeight = Math.max(maxHeight, size.y); } int width = 0, height = 0; if (type == SWT.HORIZONTAL) { width = count * maxWidth; if (count != 0) width += (count - 1) * spacing; height = maxHeight; } else { width = maxWidth; height = count * maxHeight; if (count != 0) height += (count - 1) * spacing; } width += marginWidth * 2; height += marginHeight * 2; if (wHint != SWT.DEFAULT) width = wHint; if (hHint != SWT.DEFAULT) height = hHint; return new Point(width, height); } Point computeChildSize(Control control, int wHint, int hHint, boolean flushCache) { FillData data = (FillData) control.getLayoutData(); if (data == null) { data = new FillData(); control.setLayoutData(data); } Point size = null; if (wHint == SWT.DEFAULT && hHint == SWT.DEFAULT) { size = data.computeSize(control, wHint, hHint, flushCache); } else { // TEMPORARY CODE int trimX, trimY; if (control instanceof Scrollable) { Rectangle rect = ((Scrollable) control).computeTrim(0, 0, 0, 0); trimX = rect.width; trimY = rect.height; } else { trimX = trimY = control.getBorderWidth() * 2; } int w = wHint == SWT.DEFAULT ? wHint : Math.max(0, wHint - trimX); int h = hHint == SWT.DEFAULT ? hHint : Math.max(0, hHint - trimY); size = data.computeSize(control, w, h, flushCache); } return size; } @Override protected boolean flushCache(Control control) { Object data = control.getLayoutData(); if (data != null) ((FillData) data).flushCache(); return true; } String getName() { String string = getClass().getName(); int index = string.lastIndexOf('.'); if (index == -1) return string; return string.substring(index + 1, string.length()); } @Override protected void layout(Composite composite, boolean flushCache) { Rectangle rect = composite.getClientArea(); Control[] children = composite.getChildren(); int count = children.length; if (count == 0) return; int width = rect.width - marginWidth * 2; int height = rect.height - marginHeight * 2; if (type == SWT.HORIZONTAL) { width -= (count - 1) * spacing; int x = rect.x + marginWidth, extra = width % count; int y = rect.y + marginHeight, cellWidth = width / count; for (int i = 0; i < count; i++) { Control child = children[i]; int childWidth = cellWidth; if (i == 0) { childWidth += extra / 2; } else { if (i == count - 1) childWidth += (extra + 1) / 2; } child.setBounds(x, y, childWidth, height); x += childWidth + spacing; } } else { height -= (count - 1) * spacing; int x = rect.x + marginWidth, cellHeight = height / count; int y = rect.y + marginHeight, extra = height % count; for (int i = 0; i < count; i++) { Control child = children[i]; int childHeight = cellHeight; if (i == 0) { childHeight += extra / 2; } else { if (i == count - 1) childHeight += (extra + 1) / 2; } child.setBounds(x, y, width, childHeight); y += childHeight + spacing; } } } /** * Returns a string containing a concise, human-readable * description of the receiver. * * @return a string representation of the layout */ @Override public String toString() { String string = getName() + " {"; string += "type=" + ((type == SWT.VERTICAL) ? "SWT.VERTICAL" : "SWT.HORIZONTAL") + " "; if (marginWidth != 0) string += "marginWidth=" + marginWidth + " "; if (marginHeight != 0) string += "marginHeight=" + marginHeight + " "; if (spacing != 0) string += "spacing=" + spacing + " "; string = string.trim(); string += "}"; return string; } }