/*******************************************************************************
* 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.ui.internal.menus;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.CoolBar;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.ToolBar;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.internal.WorkbenchPlugin;
import org.eclipse.ui.menus.AbstractWorkbenchTrimWidget;
import org.eclipse.ui.menus.IWorkbenchWidget;
/**
* <p>
* A proxy for a widget that has been defined in XML. This delays the class
* loading until the widget is really asked to fill a menu collection. Asking
* the widget for anything will instantiate the class.
* </p>
*
* @since 3.2
*/
final class WidgetProxy implements IWorkbenchWidget {
/**
* Used to determine whether the load has been tried to
* prevent multiple retries at a failed load.
*/
private boolean firstLoad = true;
/**
* The configuration element from which the widget can be created. This
* value will exist until the element is converted into a real class -- at
* which point this value will be set to <code>null</code>.
*/
private IConfigurationElement configurationElement;
/**
* The real widget. This value is <code>null</code> until the proxy is
* forced to load the real widget. At this point, the configuration element
* is converted, nulled out, and this widget gains a reference.
*/
private IWorkbenchWidget widget = null;
/**
* The name of the configuration element attribute which contains the
* information necessary to instantiate the real widget.
*/
private final String widgetAttributeName;
/**
* Constructs a new instance of <code>WidgetProxy</code> with all the
* information it needs to try to load the class at a later point in time.
*
* @param configurationElement
* The configuration element from which the real class can be
* loaded at run-time; must not be <code>null</code>.
* @param widgetAttributeName
* The name of the attibute or element containing the widget
* executable extension; must not be <code>null</code>.
*/
public WidgetProxy(final IConfigurationElement configurationElement,
final String widgetAttributeName) {
if (configurationElement == null) {
throw new NullPointerException(
"The configuration element backing a widget proxy cannot be null"); //$NON-NLS-1$
}
if (widgetAttributeName == null) {
throw new NullPointerException(
"The attribute containing the widget class must be known"); //$NON-NLS-1$
}
this.configurationElement = configurationElement;
this.widgetAttributeName = widgetAttributeName;
}
public final void dispose() {
if (loadWidget()) {
widget.dispose();
}
}
public final void fill(final Composite parent) {
if (loadWidget()) {
widget.fill(parent);
}
}
public final void fill(final CoolBar parent, final int index) {
if (loadWidget()) {
widget.fill(parent, index);
}
}
public final void fill(final Menu parent, final int index) {
if (loadWidget()) {
widget.fill(parent, index);
}
}
public final void fill(final ToolBar parent, final int index) {
if (loadWidget()) {
widget.fill(parent, index);
}
}
/* (non-Javadoc)
* @see org.eclipse.ui.menus.IWorkbenchWidget#init(org.eclipse.ui.IWorkbenchWindow)
*/
public void init(IWorkbenchWindow workbenchWindow) {
if (loadWidget()) {
widget.init(workbenchWindow);
}
}
/**
* Convenience method that allows the trim layout manager to
* inform widgets if they have changed locations. If the IWidget
* implementation does not support the method then we default
* to using the simpler <code>fill(final Composite parent)</code>.
*
* @param parent The composite to create the controls in
* @param oldSide The side the trim was previously displayed on
* @param newSide The new side that the trim will be displayed on
*/
public final void fill(Composite parent, int oldSide, int newSide) {
if (loadWidget()) {
if (isMoveableTrimWidget()) {
((AbstractWorkbenchTrimWidget) widget).fill(parent, oldSide, newSide);
} else {
widget.fill(parent);
}
}
}
/**
* Loads the widget, if possible. If the widget is loaded, then the member
* variables are updated accordingly.
*
* @return <code>true</code> if the widget is now non-null;
* <code>false</code> otherwise.
*/
private final boolean loadWidget() {
if (firstLoad) {
// Load the handler.
try {
widget = (IWorkbenchWidget) configurationElement
.createExecutableExtension(widgetAttributeName);
configurationElement = null;
} catch (final ClassCastException e) {
final String message = "The proxied widget was the wrong class"; //$NON-NLS-1$
final IStatus status = new Status(IStatus.ERROR,
WorkbenchPlugin.PI_WORKBENCH, 0, message, e);
WorkbenchPlugin.log(message, status);
} catch (final CoreException e) {
final String message = "The proxied widget for '" + configurationElement.getAttribute(widgetAttributeName) //$NON-NLS-1$
+ "' could not be loaded"; //$NON-NLS-1$
IStatus status = new Status(IStatus.ERROR,
WorkbenchPlugin.PI_WORKBENCH, 0, message, e);
WorkbenchPlugin.log(message, status);
}
}
// We're througth the first load
firstLoad = false;
// the load only succeeded if there's a widget..
return widget != null;
}
/**
* Determine if the widget knows how to respond to changes in the
* workbench 'side' that it is being displayed on.
*
* @return <code>true</code> iff the <code>IWidget</code> implementation
* is actually based on <code>AbstractTrimWidget</code>
*/
private final boolean isMoveableTrimWidget() {
if (loadWidget()) {
return widget instanceof AbstractWorkbenchTrimWidget;
}
return false;
}
public final String toString() {
if (widget == null) {
return configurationElement.getAttribute(widgetAttributeName);
}
return widget.toString();
}
}