1 files changed, 138 insertions, 0 deletions
diff --git a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/decorators/GitDecorator.java b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/decorators/GitDecorator.java
new file mode 100644
index 0000000000..f3619767b8
--- /dev/null
+++ b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/decorators/GitDecorator.java
@@ -0,0 +1,138 @@
+/*******************************************************************************
+ * Copyright (C) 2018, Thomas Wolf <thomas.wolf@paranor.ch>
+ *
+ * All rights reserved. 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
+ *******************************************************************************/
+package org.eclipse.egit.ui.internal.decorators;
+
+import java.text.MessageFormat;
+
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.core.runtime.jobs.Job;
+import org.eclipse.egit.core.internal.indexdiff.IndexDiffChangedListener;
+import org.eclipse.egit.core.internal.indexdiff.IndexDiffData;
+import org.eclipse.egit.ui.internal.UIText;
+import org.eclipse.jface.viewers.ILightweightLabelDecorator;
+import org.eclipse.jface.viewers.LabelProvider;
+import org.eclipse.jface.viewers.LabelProviderChangedEvent;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.ui.PlatformUI;
+
+/**
+ * Abstract base class for git decorators. It automatically listens to index
+ * changes and fires {@link LabelProviderChangedEvent}s when the index diff
+ * changes.
+ */
+public abstract class GitDecorator extends LabelProvider
+		implements ILightweightLabelDecorator, IndexDiffChangedListener {
+
+	private Object lock = new Object();
+
+	/** Protected by lock's monitor. */
+	private EventJob eventJob;
+
+	/**
+	 * Creates a new {@link GitDecorator}, registering to receive notifications
+	 * about index changes.
+	 */
+	public GitDecorator() {
+		org.eclipse.egit.core.Activator.getDefault().getIndexDiffCache()
+				.addIndexDiffChangedListener(this);
+	}
+
+	@Override
+	public void dispose() {
+		org.eclipse.egit.core.Activator.getDefault().getIndexDiffCache()
+				.removeIndexDiffChangedListener(this);
+		Job job;
+		synchronized (lock) {
+			job = eventJob;
+			eventJob = null;
+		}
+		if (job != null) {
+			job.cancel();
+		}
+	}
+
+	/**
+	 * Posts an asynchronous {@link LabelProviderChangedEvent} invalidating all
+	 * labels.
+	 */
+	protected void postLabelEvent() {
+		getEventJob().post(this);
+	}
+
+	/**
+	 * Posts a {@link LabelProviderChangedEvent} invalidating all labels.
+	 */
+	protected void fireLabelEvent() {
+		LabelProviderChangedEvent event = new LabelProviderChangedEvent(this);
+		// Re-trigger decoration process (in UI thread)
+		PlatformUI.getWorkbench().getDisplay()
+				.asyncExec(() -> fireLabelProviderChanged(event));
+	}
+
+	@Override
+	public void indexDiffChanged(Repository repository,
+			IndexDiffData indexDiffData) {
+		postLabelEvent();
+	}
+
+	private EventJob getEventJob() {
+		synchronized (lock) {
+			if (eventJob == null) {
+				eventJob = new EventJob(getName());
+				eventJob.setSystem(true);
+				eventJob.setUser(false);
+			}
+			return eventJob;
+		}
+	}
+
+	/**
+	 * @return a human-readable name for this decorator
+	 */
+	protected abstract String getName();
+
+	/**
+	 * Job reducing label events to prevent unnecessary (i.e. redundant) event
+	 * processing. Each instance of a {@link GitDecorator} gets its own job.
+	 */
+	private static class EventJob extends Job {
+
+		/**
+		 * Constant defining the waiting time (in milliseconds) until an event
+		 * is fired
+		 */
+		private static final long DELAY = 100L;
+
+		private GitDecorator decorator;
+
+		public EventJob(String name) {
+			super(MessageFormat.format(UIText.GitDecorator_jobTitle, name));
+		}
+
+		@Override
+		public IStatus run(IProgressMonitor monitor) {
+			if (decorator != null) {
+				decorator.fireLabelEvent();
+			}
+			return Status.OK_STATUS;
+		}
+
+		public void post(GitDecorator source) {
+			this.decorator = source;
+			if (getState() == SLEEPING || getState() == WAITING) {
+				cancel();
+			}
+			schedule(DELAY);
+		}
+	}
+}