Updatethrottle singleton

app/display/representation/src/main/java/org/csstudio/display/builder/representation/RepresentationUpdateThrottle.java

@@ -15,7 +15,7 @@
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.Level;
 
 /** Handle throttled updates on UI thread.
@@ -38,9 +38,6 @@
 @SuppressWarnings("nls")
 public class RepresentationUpdateThrottle
 {
-    /** Instance counter to aid in debugging the throttle start/shutdown */
-    private static final AtomicInteger instance = new AtomicInteger();
-
     /** Period in seconds for logging update performance */
     private static final int performance_log_period_secs = Preferences.performance_log_period_secs;
 
@@ -53,6 +50,9 @@
     /** Pause between updates to prevent flooding the UI thread */
     private static final long update_delay = Preferences.update_delay;
 
+    /** Singleton instance of this class */
+    private static RepresentationUpdateThrottle instance;
+
     /** Executor for UI thread */
     private final Executor gui_executor;
 
@@ -73,10 +73,23 @@
      */
     private final Set<WidgetRepresentation<?, ?, ?>> updateable = new LinkedHashSet<>();
 
+    /** Get instance of this class to perform updates on the UI thread. This class
+     * is a singleton to ensure that only one thread is scheduling jobs on the UI
+     * thread.
+     *
+     *  @param gui_executor Executor for UI thread
+     */
+    public static RepresentationUpdateThrottle getInstance(final Executor gui_executor) {
+        if(instance == null) {
+            instance = new RepresentationUpdateThrottle(gui_executor);
+        }
+        return instance;
+    }
+
     /** @param gui_executor Executor for UI thread */
-    public RepresentationUpdateThrottle(final Executor gui_executor)
+    private RepresentationUpdateThrottle(final Executor gui_executor)
     {
-        final String name = "RepresentationUpdateThrottle" + instance.incrementAndGet();
+        final String name = "RepresentationUpdateThrottle";
         logger.log(Level.FINE, "Create " + name);
         this.gui_executor = gui_executor;
         throttle_thread = new Thread(this::doRun);

app/display/representation/src/main/java/org/csstudio/display/builder/representation/ToolkitRepresentation.java

@@ -74,7 +74,7 @@ abstract public class ToolkitRepresentation<TWP extends Object, TW> implements E
 
     private final boolean edit_mode;
 
-    private final RepresentationUpdateThrottle throttle = new RepresentationUpdateThrottle(this);
+    private final RepresentationUpdateThrottle throttle = RepresentationUpdateThrottle.getInstance(this);
 
     /**
      * Listener list

app/display/representation/src/test/java/org/csstudio/display/builder/representation/UpdateThrottleTest.java

@@ -28,7 +28,7 @@
 @SuppressWarnings("nls")
 public class UpdateThrottleTest
 {
-    private final RepresentationUpdateThrottle throttle = new RepresentationUpdateThrottle(Executors.newSingleThreadExecutor());
+    private final RepresentationUpdateThrottle throttle = RepresentationUpdateThrottle.getInstance(Executors.newSingleThreadExecutor());
 
     private class TestWidgetRepresentation extends WidgetRepresentation<Object, Object, Widget>
     {