org.eclipse.swt.custom.ControlEditor.java Source code

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/*******************************************************************************
 * 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
 *******************************************************************************/
package org.eclipse.swt.custom;

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.internal.SerializableCompatibility;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.ScrollBar;

/**
 * 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: <code><pre>
 * 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);
 * </pre></code>
 *
 * @since 1.0
 */
public class ControlEditor implements SerializableCompatibility {

    /**
     * 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 = new Listener() {
            public void handleEvent(Event e) {
                layout();
            }
        };
        for (int i = 0; i < EVENTS.length; i++) {
            parent.addListener(EVENTS[i], controlListener);
        }
        scrollbarListener = new Listener() {
            public void handleEvent(Event e) {
                scroll(e);
            }
        };
        ScrollBar hBar = parent.getHorizontalBar();
        ScrollBar vBar = parent.getVerticalBar();
        if (hBar != null) {
            hBar.addListener(SWT.Selection, scrollbarListener);
        }
        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();
            ScrollBar vBar = parent.getVerticalBar();
            if (hBar != null) {
                hBar.removeListener(SWT.Selection, scrollbarListener);
            }
            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.
     */
    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);
    }
}