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.*; /** * Instances of this class determine the size and position of the * children of a <code>Composite</code> by placing them either in * horizontal rows or vertical columns within the parent <code>Composite</code>. * <p> * <code>RowLayout</code> aligns all controls in one row if the * <code>type</code> is set to horizontal, and one column if it is * set to vertical. It has the ability to wrap, and provides configurable * margins and spacing. <code>RowLayout</code> has a number of configuration * fields. In addition, the height and width of each control in a * <code>RowLayout</code> can be specified by setting a <code>RowData</code> * object into the control using <code>setLayoutData ()</code>. * </p> * <p> * The following example code creates a <code>RowLayout</code>, sets all * of its fields to non-default values, and then sets it into a * <code>Shell</code>.</p> * <pre> * RowLayout rowLayout = new RowLayout(); * rowLayout.wrap = false; * rowLayout.pack = false; * rowLayout.justify = true; * rowLayout.type = SWT.VERTICAL; * rowLayout.marginLeft = 5; * rowLayout.marginTop = 5; * rowLayout.marginRight = 5; * rowLayout.marginBottom = 5; * rowLayout.spacing = 0; * shell.setLayout(rowLayout); * </pre> * If you are using the default field values, you only need one line of code: * <pre> * shell.setLayout(new RowLayout()); * </pre> * * @see RowData * @see <a href="http://www.eclipse.org/swt/snippets/#rowlayout">RowLayout snippets</a> * @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 RowLayout extends Layout { /** * type specifies whether the layout places controls in rows or * columns. * * 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> * * @since 2.0 */ 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 3. */ public int spacing = 3; /** * wrap specifies whether a control will be wrapped to the next * row if there is insufficient space on the current row. * * The default value is true. */ public boolean wrap = true; /** * pack specifies whether all controls in the layout take * their preferred size. If pack is false, all controls will * have the same size which is the size required to accommodate the * largest preferred height and the largest preferred width of all * the controls in the layout. * * The default value is true. */ public boolean pack = true; /** * fill specifies whether the controls in a row should be * all the same height for horizontal layouts, or the same * width for vertical layouts. * * The default value is false. * * @since 3.0 */ public boolean fill = false; /** * center specifies whether the controls in a row should be * centered vertically in each cell for horizontal layouts, * or centered horizontally in each cell for vertical layouts. * * The default value is false. * * @since 3.4 */ public boolean center = false; /** * justify specifies whether the controls in a row should be * fully justified, with any extra space placed between the controls. * * The default value is false. */ public boolean justify = false; /** * marginLeft specifies the number of points of horizontal margin * that will be placed along the left edge of the layout. * * The default value is 3. */ public int marginLeft = 3; /** * marginTop specifies the number of points of vertical margin * that will be placed along the top edge of the layout. * * The default value is 3. */ public int marginTop = 3; /** * marginRight specifies the number of points of horizontal margin * that will be placed along the right edge of the layout. * * The default value is 3. */ public int marginRight = 3; /** * marginBottom specifies the number of points of vertical margin * that will be placed along the bottom edge of the layout. * * The default value is 3. */ public int marginBottom = 3; /** * Constructs a new instance of this class with type HORIZONTAL. */ public RowLayout() { } /** * Constructs a new instance of this class given the type. * * @param type the type of row layout * * @since 2.0 */ public RowLayout(int type) { this.type = type; } @Override protected Point computeSize(Composite composite, int wHint, int hHint, boolean flushCache) { Point extent; if (type == SWT.HORIZONTAL) { extent = layoutHorizontal(composite, false, (wHint != SWT.DEFAULT) && wrap, wHint, flushCache); } else { extent = layoutVertical(composite, false, (hHint != SWT.DEFAULT) && wrap, hHint, flushCache); } if (wHint != SWT.DEFAULT) extent.x = wHint; if (hHint != SWT.DEFAULT) extent.y = hHint; return extent; } Point computeSize(Control control, boolean flushCache) { int wHint = SWT.DEFAULT, hHint = SWT.DEFAULT; RowData data = (RowData) control.getLayoutData(); if (data != null) { wHint = data.width; hHint = data.height; } return control.computeSize(wHint, hHint, flushCache); } @Override protected boolean flushCache(Control control) { 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 clientArea = composite.getClientArea(); if (type == SWT.HORIZONTAL) { layoutHorizontal(composite, true, wrap, clientArea.width, flushCache); } else { layoutVertical(composite, true, wrap, clientArea.height, flushCache); } } Point layoutHorizontal(Composite composite, boolean move, boolean wrap, int width, boolean flushCache) { Control[] children = composite.getChildren(); int count = 0; for (int i = 0; i < children.length; i++) { Control control = children[i]; RowData data = (RowData) control.getLayoutData(); if (data == null || !data.exclude) { children[count++] = children[i]; } } if (count == 0) { return new Point(marginLeft + marginWidth * 2 + marginRight, marginTop + marginHeight * 2 + marginBottom); } int childWidth = 0, childHeight = 0, maxHeight = 0; if (!pack) { for (int i = 0; i < count; i++) { Control child = children[i]; Point size = computeSize(child, flushCache); if (width > SWT.DEFAULT && width < size.x && wrap) { size = child.computeSize(width, child.getLayoutData() == null ? SWT.DEFAULT : ((RowData) child.getLayoutData()).height, flushCache); } childWidth = Math.max(childWidth, size.x); childHeight = Math.max(childHeight, size.y); } maxHeight = childHeight; } int clientX = 0, clientY = 0; if (move) { Rectangle rect = composite.getClientArea(); clientX = rect.x; clientY = rect.y; } int[] wraps = null; boolean wrapped = false; Rectangle[] bounds = null; if (move && (justify || fill || center)) { bounds = new Rectangle[count]; wraps = new int[count]; } int maxX = 0, x = marginLeft + marginWidth, y = marginTop + marginHeight; for (int i = 0; i < count; i++) { Control child = children[i]; if (pack) { Point size = computeSize(child, flushCache); if (width > SWT.DEFAULT && width < size.x && wrap) { size = child.computeSize(width, child.getLayoutData() == null ? SWT.DEFAULT : ((RowData) child.getLayoutData()).height, flushCache); } childWidth = size.x; childHeight = size.y; } if (wrap && (i != 0) && (x + childWidth > width)) { wrapped = true; if (move && (justify || fill || center)) wraps[i - 1] = maxHeight; x = marginLeft + marginWidth; y += spacing + maxHeight; if (pack) maxHeight = 0; } if (pack || fill || center) { maxHeight = Math.max(maxHeight, childHeight); } if (move) { int childX = x + clientX, childY = y + clientY; if (justify || fill || center) { bounds[i] = new Rectangle(childX, childY, childWidth, childHeight); } else { child.setBounds(childX, childY, childWidth, childHeight); } } x += spacing + childWidth; maxX = Math.max(maxX, x); } maxX = Math.max(clientX + marginLeft + marginWidth, maxX - spacing); if (!wrapped) maxX += marginRight + marginWidth; if (move && (justify || fill || center)) { int space = 0, margin = 0; if (!wrapped) { space = Math.max(0, (width - maxX) / (count + 1)); margin = Math.max(0, ((width - maxX) % (count + 1)) / 2); } else { if (fill || justify || center) { int last = 0; if (count > 0) wraps[count - 1] = maxHeight; for (int i = 0; i < count; i++) { if (wraps[i] != 0) { int wrapCount = i - last + 1; if (justify) { int wrapX = 0; for (int j = last; j <= i; j++) { wrapX += bounds[j].width + spacing; } space = Math.max(0, (width - wrapX) / (wrapCount + 1)); margin = Math.max(0, ((width - wrapX) % (wrapCount + 1)) / 2); } for (int j = last; j <= i; j++) { if (justify) bounds[j].x += (space * (j - last + 1)) + margin; if (fill) { bounds[j].height = wraps[i]; } else { if (center) { bounds[j].y += Math.max(0, (wraps[i] - bounds[j].height) / 2); } } } last = i + 1; } } } } for (int i = 0; i < count; i++) { if (!wrapped) { if (justify) bounds[i].x += (space * (i + 1)) + margin; if (fill) { bounds[i].height = maxHeight; } else { if (center) { bounds[i].y += Math.max(0, (maxHeight - bounds[i].height) / 2); } } } children[i].setBounds(bounds[i]); } } return new Point(maxX, y + maxHeight + marginBottom + marginHeight); } Point layoutVertical(Composite composite, boolean move, boolean wrap, int height, boolean flushCache) { Control[] children = composite.getChildren(); int count = 0; for (int i = 0; i < children.length; i++) { Control control = children[i]; RowData data = (RowData) control.getLayoutData(); if (data == null || !data.exclude) { children[count++] = children[i]; } } if (count == 0) { return new Point(marginLeft + marginWidth * 2 + marginRight, marginTop + marginHeight * 2 + marginBottom); } int childWidth = 0, childHeight = 0, maxWidth = 0; if (!pack) { for (int i = 0; i < count; i++) { Control child = children[i]; Point size = computeSize(child, flushCache); if (height > SWT.DEFAULT && height < size.y && wrap) size = child.computeSize( child.getLayoutData() == null ? SWT.DEFAULT : ((RowData) child.getLayoutData()).width, height, flushCache); childWidth = Math.max(childWidth, size.x); childHeight = Math.max(childHeight, size.y); } maxWidth = childWidth; } int clientX = 0, clientY = 0; if (move) { Rectangle rect = composite.getClientArea(); clientX = rect.x; clientY = rect.y; } int[] wraps = null; boolean wrapped = false; Rectangle[] bounds = null; if (move && (justify || fill || center)) { bounds = new Rectangle[count]; wraps = new int[count]; } int maxY = 0, x = marginLeft + marginWidth, y = marginTop + marginHeight; for (int i = 0; i < count; i++) { Control child = children[i]; if (pack) { Point size = computeSize(child, flushCache); if (height > SWT.DEFAULT && height < size.y && wrap) size = child.computeSize( child.getLayoutData() == null ? SWT.DEFAULT : ((RowData) child.getLayoutData()).width, height, flushCache); childWidth = size.x; childHeight = size.y; } if (wrap && (i != 0) && (y + childHeight > height)) { wrapped = true; if (move && (justify || fill || center)) wraps[i - 1] = maxWidth; x += spacing + maxWidth; y = marginTop + marginHeight; if (pack) maxWidth = 0; } if (pack || fill || center) { maxWidth = Math.max(maxWidth, childWidth); } if (move) { int childX = x + clientX, childY = y + clientY; if (justify || fill || center) { bounds[i] = new Rectangle(childX, childY, childWidth, childHeight); } else { child.setBounds(childX, childY, childWidth, childHeight); } } y += spacing + childHeight; maxY = Math.max(maxY, y); } maxY = Math.max(clientY + marginTop + marginHeight, maxY - spacing); if (!wrapped) maxY += marginBottom + marginHeight; if (move && (justify || fill || center)) { int space = 0, margin = 0; if (!wrapped) { space = Math.max(0, (height - maxY) / (count + 1)); margin = Math.max(0, ((height - maxY) % (count + 1)) / 2); } else { if (fill || justify || center) { int last = 0; if (count > 0) wraps[count - 1] = maxWidth; for (int i = 0; i < count; i++) { if (wraps[i] != 0) { int wrapCount = i - last + 1; if (justify) { int wrapY = 0; for (int j = last; j <= i; j++) { wrapY += bounds[j].height + spacing; } space = Math.max(0, (height - wrapY) / (wrapCount + 1)); margin = Math.max(0, ((height - wrapY) % (wrapCount + 1)) / 2); } for (int j = last; j <= i; j++) { if (justify) bounds[j].y += (space * (j - last + 1)) + margin; if (fill) { bounds[j].width = wraps[i]; } else { if (center) { bounds[j].x += Math.max(0, (wraps[i] - bounds[j].width) / 2); } } } last = i + 1; } } } } for (int i = 0; i < count; i++) { if (!wrapped) { if (justify) bounds[i].y += (space * (i + 1)) + margin; if (fill) { bounds[i].width = maxWidth; } else { if (center) { bounds[i].x += Math.max(0, (maxWidth - bounds[i].width) / 2); } } } children[i].setBounds(bounds[i]); } } return new Point(x + maxWidth + marginRight + marginWidth, maxY); } /** * 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.HORIZONTAL) ? "SWT.VERTICAL" : "SWT.HORIZONTAL") + " "; if (marginWidth != 0) string += "marginWidth=" + marginWidth + " "; if (marginHeight != 0) string += "marginHeight=" + marginHeight + " "; if (marginLeft != 0) string += "marginLeft=" + marginLeft + " "; if (marginTop != 0) string += "marginTop=" + marginTop + " "; if (marginRight != 0) string += "marginRight=" + marginRight + " "; if (marginBottom != 0) string += "marginBottom=" + marginBottom + " "; if (spacing != 0) string += "spacing=" + spacing + " "; string += "wrap=" + wrap + " "; string += "pack=" + pack + " "; string += "fill=" + fill + " "; string += "justify=" + justify + " "; string = string.trim(); string += "}"; return string; } }