ltk/org.eclipse.statet.ltk.ui/src/org/eclipse/statet/ecommons/ui/workbench/texteditor/ActionHandler.java

/*=============================================================================#
 # Copyright (c) 2021 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.ecommons.ui.workbench.texteditor;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.commands.HandlerEvent;
import org.eclipse.core.commands.IHandlerListener;
import org.eclipse.jface.action.IAction;
import org.eclipse.jface.util.IPropertyChangeListener;
import org.eclipse.jface.util.PropertyChangeEvent;
import org.eclipse.swt.widgets.Event;
import org.eclipse.ui.texteditor.IUpdate;

import org.eclipse.statet.jcommons.lang.NonNullByDefault;
import org.eclipse.statet.jcommons.lang.Nullable;
import org.eclipse.statet.jcommons.lang.ObjectUtils.ToStringBuilder;


@NonNullByDefault
public class ActionHandler extends AbstractHandler {
	
	
	private final IAction action;
	
	private boolean isDisposed;
	
	private @Nullable IPropertyChangeListener propertyChangeListener;
	
	
	public ActionHandler(final IAction action) {
		this.action= action;
	}
	
	@Override
	public void dispose() {
		this.isDisposed= true;
		detachListener();
		super.dispose();
	}
	
	
	public final IAction getAction() {
		return this.action;
	}
	
	
	@Override
	public void addHandlerListener(final IHandlerListener handlerListener) {
		if (this.isDisposed) {
			return;
		}
		if (!hasListeners()) {
			attachListener();
		}
		super.addHandlerListener(handlerListener);
	}
	
	private void attachListener() {
		if (this.propertyChangeListener == null) {
			final var listener= new IPropertyChangeListener() {
				@Override
				public void propertyChange(final PropertyChangeEvent event) {
					final String property= event.getProperty();
					fireHandlerChanged(new HandlerEvent(ActionHandler.this,
							IAction.ENABLED.equals(property),
							IAction.HANDLED.equals(property) ));
				}
			};
			this.propertyChangeListener= listener;
		}
		this.action.addPropertyChangeListener(this.propertyChangeListener);
	}
	
	private void detachListener() {
		final var listener= this.propertyChangeListener;
		if (listener != null) {
			this.propertyChangeListener= null;
			this.action.removePropertyChangeListener(listener);
		}
	}
	
	
	@Override
	public void setEnabled(final @Nullable Object evaluationContext) {
		if (this.action instanceof IUpdate) {
			((IUpdate)this.action).update();
		}
		setBaseEnabled(this.action.isEnabled());
	}
	
	@Override
	public final @Nullable Object execute(final ExecutionEvent event)
			throws ExecutionException {
		if ((this.action.getStyle() == IAction.AS_CHECK_BOX)
				|| (this.action.getStyle() == IAction.AS_RADIO_BUTTON)) {
			this.action.setChecked(!this.action.isChecked());
		}
		try {
			final Object trigger= event.getTrigger();
			final Event swtEvent= (trigger instanceof Event) ? (Event)trigger : new Event();
			this.action.runWithEvent(swtEvent);
			return null;
		}
		catch (final Exception e) {
			throw new ExecutionException(e.getMessage(), e);
		}
	}
	
	@Override
	public boolean isHandled() {
		return this.action.isHandled();
	}
	
	@Override
	public boolean isEnabled() {
		return this.action.isEnabled();
	}
	
	
	@Override
	public final String toString() {
		final ToStringBuilder sb= new ToStringBuilder(ActionHandler.class);
		sb.append(' ', this.action.toString());
		return sb.toString();
	}
	
}