Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2016 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.custom; import org.eclipse.swt.*; import org.eclipse.swt.graphics.*; import org.eclipse.swt.widgets.*; /** * * A ControlEditor is a manager for a Control that appears above a composite and tracks with the * moving and resizing of that composite. It can be used to display one control above * another control. This could be used when editing a control that does not have editing * capabilities by using a text editor or for launching a dialog by placing a button * above a control. * * <p> Here is an example of using a ControlEditor:</p> * * <pre><code> * Canvas canvas = new Canvas(shell, SWT.BORDER); * canvas.setBounds(10, 10, 300, 300); * Color color = new Color(null, 255, 0, 0); * canvas.setBackground(color); * ControlEditor editor = new ControlEditor (canvas); * // The editor will be a button in the bottom right corner of the canvas. * // When selected, it will launch a Color dialog that will change the background * // of the canvas. * Button button = new Button(canvas, SWT.PUSH); * button.setText("Select Color..."); * button.addSelectionListener (new SelectionAdapter() { * public void widgetSelected(SelectionEvent e) { * ColorDialog dialog = new ColorDialog(shell); * dialog.open(); * RGB rgb = dialog.getRGB(); * if (rgb != null) { * if (color != null) color.dispose(); * color = new Color(null, rgb); * canvas.setBackground(color); * } * * } * }); * * editor.horizontalAlignment = SWT.RIGHT; * editor.verticalAlignment = SWT.BOTTOM; * editor.grabHorizontal = false; * editor.grabVertical = false; * Point size = button.computeSize(SWT.DEFAULT, SWT.DEFAULT); * editor.minimumWidth = size.x; * editor.minimumHeight = size.y; * editor.setEditor (button); * </code></pre> * * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a> */ public class ControlEditor { /** * Specifies how the editor should be aligned relative to the control. Allowed values * are SWT.LEFT, SWT.RIGHT and SWT.CENTER. The default value is SWT.CENTER. */ public int horizontalAlignment = SWT.CENTER; /** * Specifies whether the editor should be sized to use the entire width of the control. * True means resize the editor to the same width as the cell. False means do not adjust * the width of the editor. The default value is false. */ public boolean grabHorizontal = false; /** * Specifies the minimum width the editor can have. This is used in association with * a true value of grabHorizontal. If the cell becomes smaller than the minimumWidth, the * editor will not made smaller than the minimum width value. The default value is 0. */ public int minimumWidth = 0; /** * Specifies how the editor should be aligned relative to the control. Allowed values * are SWT.TOP, SWT.BOTTOM and SWT.CENTER. The default value is SWT.CENTER. */ public int verticalAlignment = SWT.CENTER; /** * Specifies whether the editor should be sized to use the entire height of the control. * True means resize the editor to the same height as the underlying control. False means do not adjust * the height of the editor. The default value is false. */ public boolean grabVertical = false; /** * Specifies the minimum height the editor can have. This is used in association with * a true value of grabVertical. If the control becomes smaller than the minimumHeight, the * editor will not made smaller than the minimum height value. The default value is 0. */ public int minimumHeight = 0; Composite parent; Control editor; private boolean hadFocus; private Listener controlListener; private Listener scrollbarListener; private final static int[] EVENTS = { SWT.KeyDown, SWT.KeyUp, SWT.MouseDown, SWT.MouseUp, SWT.Resize }; /** * Creates a ControlEditor for the specified Composite. * * @param parent the Composite above which this editor will be displayed * */ public ControlEditor(Composite parent) { this.parent = parent; controlListener = e -> layout(); for (int i = 0; i < EVENTS.length; i++) { parent.addListener(EVENTS[i], controlListener); } scrollbarListener = e -> scroll(e); ScrollBar hBar = parent.getHorizontalBar(); if (hBar != null) hBar.addListener(SWT.Selection, scrollbarListener); ScrollBar vBar = parent.getVerticalBar(); if (vBar != null) vBar.addListener(SWT.Selection, scrollbarListener); } Rectangle computeBounds() { Rectangle clientArea = parent.getClientArea(); Rectangle editorRect = new Rectangle(clientArea.x, clientArea.y, minimumWidth, minimumHeight); if (grabHorizontal) editorRect.width = Math.max(clientArea.width, minimumWidth); if (grabVertical) editorRect.height = Math.max(clientArea.height, minimumHeight); switch (horizontalAlignment) { case SWT.RIGHT: editorRect.x += clientArea.width - editorRect.width; break; case SWT.LEFT: // do nothing - clientArea.x is the right answer break; default: // default is CENTER editorRect.x += (clientArea.width - editorRect.width) / 2; } switch (verticalAlignment) { case SWT.BOTTOM: editorRect.y += clientArea.height - editorRect.height; break; case SWT.TOP: // do nothing - clientArea.y is the right answer break; default: // default is CENTER editorRect.y += (clientArea.height - editorRect.height) / 2; } return editorRect; } /** * Removes all associations between the Editor and the underlying composite. The * composite and the editor Control are <b>not</b> disposed. */ public void dispose() { if (parent != null && !parent.isDisposed()) { for (int i = 0; i < EVENTS.length; i++) { parent.removeListener(EVENTS[i], controlListener); } ScrollBar hBar = parent.getHorizontalBar(); if (hBar != null) hBar.removeListener(SWT.Selection, scrollbarListener); ScrollBar vBar = parent.getVerticalBar(); if (vBar != null) vBar.removeListener(SWT.Selection, scrollbarListener); } parent = null; editor = null; hadFocus = false; controlListener = null; scrollbarListener = null; } /** * Returns the Control that is displayed above the composite being edited. * * @return the Control that is displayed above the composite being edited */ public Control getEditor() { return editor; } /** * Lays out the control within the underlying composite. This * method should be called after changing one or more fields to * force the Editor to resize. * * @since 2.1 */ public void layout() { if (editor == null || editor.isDisposed()) return; if (editor.getVisible()) { hadFocus = editor.isFocusControl(); } // this doesn't work because // resizing the column takes the focus away // before we get here editor.setBounds(computeBounds()); if (hadFocus) { if (editor == null || editor.isDisposed()) return; editor.setFocus(); } } void scroll(Event e) { if (editor == null || editor.isDisposed()) return; layout(); } /** * Specify the Control that is to be displayed. * * <p>Note: The Control provided as the editor <b>must</b> be created with its parent * being the Composite specified in the ControlEditor constructor. * * @param editor the Control that is displayed above the composite being edited */ public void setEditor(Control editor) { if (editor == null) { // this is the case where the caller is setting the editor to be blank // set all the values accordingly this.editor = null; return; } this.editor = editor; layout(); if (this.editor == null || this.editor.isDisposed()) return; editor.setVisible(true); } }