Merge branch '878-fix-disposingpolicy' into release/1.53.0

Fix disposer queue length based disposal to work properly

gitlab #878

bundles/org.simantics.modeling.ui/src/org/simantics/modeling/ui/diagramEditor/DisposingPolicy.java

 package org.simantics.modeling.ui.diagramEditor;
 
 import java.util.ArrayDeque;
+import java.util.Iterator;
 
 import org.eclipse.swt.widgets.Display;
 import org.slf4j.Logger;
@@ -25,12 +26,21 @@ public class DisposingPolicy {
     private Runnable currentlyScheduled = null;
 
     private Runnable disposeOne = () -> {
-        if(!disposerQueue.isEmpty()) {
+        // If disposeOverTime is not enabled, then base the actual disposal only on the length of the queue.
+        int queueLength = disposerQueue.size();
+        boolean debug = LOGGER.isDebugEnabled();
+        if(debug)
+            LOGGER.debug("disposeOne: queueLength: {}, maxQueueLength: {}", queueLength, maxQueueLength); //$NON-NLS-1$
+        if (!disposeOverTime && queueLength <= maxQueueLength)
+            return;
+        if(queueLength > 0) {
             Runnable runnable = disposerQueue.removeFirst();
             disposeTime.remove(runnable);
             currentlyScheduled = null;
+            if(debug)
+                LOGGER.debug("Executing disposer {}", runnable); //$NON-NLS-1$
             runnable.run();
-            if(LOGGER.isDebugEnabled())
+            if(debug)
                 LOGGER.debug("Executed disposer {}", runnable); //$NON-NLS-1$
             if(!disposerQueue.isEmpty())
                 scheduleDispose();
@@ -71,14 +81,19 @@ public class DisposingPolicy {
     }
 
     private void scheduleDispose() {
-        if (!disposeOverTime)
+        boolean debug = LOGGER.isDebugEnabled();
+        if(debug)
+            LOGGER.debug("scheduleDispose({}, {}, {})", disposeOverTime, disposerQueue.size(), maxQueueLength); //$NON-NLS-1$
+        if (!disposeOverTime && disposerQueue.size() <= maxQueueLength)
             return;
         currentlyScheduled = disposerQueue.peekFirst();
+        if (currentlyScheduled == null)
+            return;
         long delay = Math.max(
                 disposeTime.get(currentlyScheduled) - System.currentTimeMillis(),
                 MIN_DELAY);
         Display.getCurrent().timerExec((int)delay, disposeOne);
-        if(LOGGER.isDebugEnabled())
+        if(debug)
             LOGGER.debug("Scheduled disposer {} in {} ms", currentlyScheduled, delay); //$NON-NLS-1$
     }
 
@@ -93,11 +108,21 @@ public class DisposingPolicy {
             LOGGER.debug("Added disposer {}", disposer); //$NON-NLS-1$
         if(disposeTime.contains(disposer))
             return;
-        while(disposerQueue.size() >= maxQueueLength)
-            disposeOne.run();
+
+        long t = System.currentTimeMillis();
         disposerQueue.addLast(disposer);
-        disposeTime.put(disposer, System.currentTimeMillis()+disposeWaitTimeMs);
-        if(disposerQueue.size() == 1)
+        disposeTime.put(disposer, t + disposeWaitTimeMs);
+
+        // Keep the number of alive hidden diagrams under the requested amount by
+        // marking the deadline for first disposeCount disposers to be right now.
+        int disposeCount = disposerQueue.size() - maxQueueLength;
+        if (disposeCount > 0) {
+            Iterator<Runnable> it = disposerQueue.iterator();
+            for (int i = 0; i < disposeCount && it.hasNext(); ++i) {
+                disposeTime.put(it.next(), t);
+            }
+        }
+
         scheduleDispose();
     }