8262725: IGV: crash when removing all graphs in a group

Make IGV close graph views when their groups are either removed or emptied, and
avoid faulty graph view computation for empty groups.

Reviewed-by: chagedorn, rrich

Author: robcasloz

src/utils/IdealGraphVisualizer/View/src/main/java/com/sun/hotspot/igv/view/DiagramViewModel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -206,6 +206,11 @@ public void changed(DiagramViewModel source) {
         @Override
         public void changed(Group source) {
             assert source == group;
+            if (group.getGraphs().isEmpty()) {
+                // If the group has been emptied, all corresponding graph views
+                // will be closed, so do nothing.
+                return;
+            }
             filterGraphs();
             setSelectedNodes(selectedNodes);
         }

src/utils/IdealGraphVisualizer/View/src/main/java/com/sun/hotspot/igv/view/EditorTopComponent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,8 @@
 
 import com.sun.hotspot.igv.data.ChangedEvent;
 import com.sun.hotspot.igv.data.ChangedListener;
+import com.sun.hotspot.igv.data.GraphDocument;
+import com.sun.hotspot.igv.data.Group;
 import com.sun.hotspot.igv.data.InputNode;
 import com.sun.hotspot.igv.data.Properties;
 import com.sun.hotspot.igv.data.Properties.PropertyMatcher;
@@ -225,6 +227,12 @@ public void changed(DiagramViewModel source) {
                 }
             });
 
+        Group group = getDiagram().getGraph().getGroup();
+        group.getChangedEvent().addListener(g -> closeOnRemovedOrEmptyGroup());
+        if (group.getParent() instanceof GraphDocument) {
+            final GraphDocument doc = (GraphDocument) group.getParent();
+            doc.getChangedEvent().addListener(d -> closeOnRemovedOrEmptyGroup());
+        }
 
         toolBar.add(NextDiagramAction.get(NextDiagramAction.class));
         toolBar.add(PrevDiagramAction.get(PrevDiagramAction.class));
@@ -449,6 +457,14 @@ protected String preferredID() {
         return PREFERRED_ID;
     }
 
+    private void closeOnRemovedOrEmptyGroup() {
+        Group group = getDiagram().getGraph().getGroup();
+        if (!group.getParent().getElements().contains(group) ||
+            group.getGraphs().isEmpty()) {
+            close();
+        }
+    }
+
     private ChangedListener<DiagramViewModel> diagramChangedListener = new ChangedListener<DiagramViewModel>() {
 
         @Override