Use a Job as the Reconciler Thread

Currently AbstractReconciler uses a raw thread for reconciling requests
this has some pitfalls:

1) There is no way for the user to see this job even if it hangs for a
long time
2) If the job framework is suspended (e.g during init of the IDE) some
code is still executed because the reconciler is called from the
creation of the text viewer

This now replaces the bare thread with a job but retain current
behaviour / API

Author: laeubi

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/reconciler/AbstractReconciler.java

@@ -15,7 +15,10 @@
 
 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.NullProgressMonitor;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.core.runtime.jobs.Job;
 
 import org.eclipse.jface.text.DocumentEvent;
 import org.eclipse.jface.text.IDocument;
@@ -53,7 +56,7 @@ abstract public class AbstractReconciler implements IReconciler {
 	/**
 	 * Background thread for the reconciling activity.
 	 */
-	class BackgroundThread extends Thread {
+	class BackgroundThread extends Job {
 
 		/** Has the reconciler been canceled. */
 		private boolean fCanceled= false;
@@ -64,6 +67,10 @@ class BackgroundThread extends Thread {
 		/** Is a reconciling strategy active. */
 		private boolean fIsActive= false;
 
+		private volatile Thread myThread;
+
+		private boolean started;
+
 		/**
 		 * Creates a new background thread. The thread
 		 * runs with minimal priority.
@@ -72,8 +79,8 @@ class BackgroundThread extends Thread {
 		 */
 		public BackgroundThread(String name) {
 			super(name);
-			setPriority(Thread.MIN_PRIORITY);
-			setDaemon(true);
+			setPriority(Job.DECORATE);
+			setSystem(true);
 		}
 
 		/**
@@ -98,7 +105,8 @@ public synchronized boolean isDirty() {
 		/**
 		 * Cancels the background thread.
 		 */
-		public void cancel() {
+		@Override
+		protected void canceling() {
 			fCanceled= true;
 			IProgressMonitor pm= fProgressMonitor;
 			if (pm != null)
@@ -167,12 +175,12 @@ public void reset() {
 		 * </p>
 		 */
 		@Override
-		public void run() {
-
+		public IStatus run(IProgressMonitor monitor) {
+			myThread= Thread.currentThread();
 			delay();
 
 			if (fCanceled)
-				return;
+				return Status.CANCEL_STATUS;
 
 			initialProcess();
 
@@ -217,6 +225,19 @@ public void run() {
 
 				fIsActive= false;
 			}
+			myThread= null;
+			return Status.OK_STATUS;
+		}
+
+		public boolean isAlive() {
+			return myThread != null;
+		}
+
+		public synchronized void start() {
+			if (!started) {
+				started= true;
+				schedule();
+			}
 		}
 	}
 
@@ -233,7 +254,7 @@ public void documentAboutToBeChanged(DocumentEvent e) {
 		public void documentChanged(DocumentEvent e) {
 
 			if (fThread.isActive() || !fThread.isDirty() && fThread.isAlive()) {
-				if (!fIsAllowedToModifyDocument && Thread.currentThread() == fThread)
+				if (!fIsAllowedToModifyDocument && isRunningInReconcilerThread())
 					throw new UnsupportedOperationException("The reconciler thread is not allowed to modify the document"); //$NON-NLS-1$
 				aboutToBeReconciledInternal();
 			}
@@ -449,7 +470,7 @@ public void install(ITextViewer textViewer) {
 		synchronized (this) {
 			if (fThread != null)
 				return;
-			fThread= new BackgroundThread(getClass().getName());
+			fThread= new BackgroundThread(getClass().getName() + " reconciler thread"); //$NON-NLS-1$
 		}
 
 		fDirtyRegionQueue= new DirtyRegionQueue();
@@ -614,14 +635,7 @@ protected synchronized void startReconciling() {
 			return;
 
 		if (!fThread.isAlive()) {
-			try {
-				fThread.start();
-			} catch (IllegalThreadStateException e) {
-				// see https://bugs.eclipse.org/bugs/show_bug.cgi?id=40549
-				// This is the only instance where the thread is started; since
-				// we checked that it is not alive, it must be dead already due
-				// to a run-time exception or error. Exit.
-			}
+			fThread.start();
 		} else {
 			fThread.reset();
 		}
@@ -640,7 +654,10 @@ protected void reconcilerReset() {
 	 * @return <code>true</code> if running in this reconciler's background thread
 	 * @since 3.4
 	 */
-	protected boolean isRunningInReconcilerThread() {
-		return Thread.currentThread() == fThread;
+	protected synchronized boolean isRunningInReconcilerThread() {
+		if (fThread == null) {
+			return false;
+		}
+		return Thread.currentThread() == fThread.myThread;
 	}
 }