| /******************************************************************************* |
| * Copyright (c) 2009, 2013 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.e4.core.contexts; |
| |
| import java.util.Stack; |
| import org.eclipse.e4.core.internal.contexts.Computation; |
| import org.eclipse.e4.core.internal.contexts.EclipseContext; |
| |
| /** |
| * Instances of this class contain behavior that is executed within an |
| * {@link IEclipseContext}. The context records all values accessed by this |
| * object, and will re-evaluate this runnable whenever any accessed value changes. |
| * |
| * @see IEclipseContext#runAndTrack(RunAndTrack) |
| * @since 1.3 |
| */ |
| abstract public class RunAndTrack { |
| |
| /** |
| * Creates a new instance of trackable computation |
| */ |
| public RunAndTrack() { |
| // placeholder |
| } |
| |
| /** |
| * This method is initially called by the framework when an instance of this |
| * class is associated with the context via {@link IEclipseContext#runAndTrack(RunAndTrack)}. |
| * <p> |
| * After the initial call this method is executed when one or more values it retrieved |
| * from the context change. |
| * </p> |
| * @param context modified context |
| * @return <code>true</code> to continue to be called on updates; <code>false</code> otherwise |
| */ |
| abstract public boolean changed(IEclipseContext context); |
| |
| /** |
| * Use this method to wrap calls to external code. For instance, while in {@link #changed(IEclipseContext)}. |
| * consider calling listeners from this method. This wrapper will pause dependency recording while |
| * in the 3rd party code, reducing potential dependency circularity issues. |
| * @param runnable |
| */ |
| synchronized protected void runExternalCode(Runnable runnable) { |
| Stack<Computation> computationStack = EclipseContext.getCalculatedComputations(); |
| computationStack.push(null); |
| try { |
| runnable.run(); |
| } finally { |
| computationStack.pop(); |
| } |
| } |
| |
| } |