Merge branch 'bug/JAL-2864nullOverviewCanvas' into develop

diff --combined src/jalview/appletgui/OverviewCanvas.java
index e99c021,03c93fa..07f5919
--- 1/src/jalview/appletgui/OverviewCanvas.java
--- 2/src/jalview/appletgui/OverviewCanvas.java
+++ b/src/jalview/appletgui/OverviewCanvas.java
@@@ -128,9 -128,11 +128,9 @@@ public class OverviewCanvas extends Com
      {
        mg.translate(0, od.getSequencesHeight());
        or.drawGraph(mg, av.getAlignmentConservationAnnotation(),
 -              av.getCharWidth(), od.getGraphHeight(),
 -              od.getColumns(av.getAlignment()));
 +              od.getGraphHeight(), od.getColumns(av.getAlignment()));
        mg.translate(0, -od.getSequencesHeight());
      }
 -    System.gc();
  
      if (restart)
      {
@@@ -162,4 -164,12 +162,12 @@@
      }
    }
  
+   /**
+    * Nulls references to protect against potential memory leaks
+    */
+   void dispose()
+   {
+     od = null;
+   }
+ 
  }

diff --combined src/jalview/appletgui/OverviewPanel.java
index 3bbbe95,4f47913..5081509
--- 1/src/jalview/appletgui/OverviewPanel.java
--- 2/src/jalview/appletgui/OverviewPanel.java
+++ b/src/jalview/appletgui/OverviewPanel.java
@@@ -155,10 -155,6 +155,10 @@@ public class OverviewPanel extends Pane
        if (!od.isPositionInBox(evt.getX(), evt.getY()))
        { 
        draggingBox = false;
 +
 +        // display drag cursor at mouse position
 +        setCursor(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR));
 +
          od.updateViewportFromMouse(evt.getX(), evt.getY(),
                  av.getAlignment().getHiddenSequences(),
                  av.getAlignment().getHiddenColumns());
@@@ -176,7 -172,6 +176,7 @@@
    @Override
    public void mouseReleased(MouseEvent evt)
    {
 +    draggingBox = false;
    }
  
    @Override
@@@ -334,6 -329,10 +334,10 @@@
      } finally
      {
        av = null;
+       if (oviewCanvas != null)
+       {
+         oviewCanvas.dispose();
+       }
        oviewCanvas = null;
        ap = null;
        od = null;

diff --combined src/jalview/gui/OverviewCanvas.java
index cc361a5,de16b00..89088b8
--- 1/src/jalview/gui/OverviewCanvas.java
--- 2/src/jalview/gui/OverviewCanvas.java
+++ b/src/jalview/gui/OverviewCanvas.java
@@@ -157,9 -157,11 +157,9 @@@ public class OverviewCanvas extends JCo
      {
        mg.translate(0, od.getSequencesHeight());
        or.drawGraph(mg, av.getAlignmentConservationAnnotation(),
 -              av.getCharWidth(), od.getGraphHeight(),
 -              od.getColumns(av.getAlignment()));
 +              od.getGraphHeight(), od.getColumns(av.getAlignment()));
        mg.translate(0, -od.getSequencesHeight());
      }
 -    System.gc();
  
      or.removePropertyChangeListener(progressPanel);
      or = null;
@@@ -181,7 -183,7 +181,7 @@@
    @Override
    public void paintComponent(Graphics g)
    {
 -    // super.paintComponent(g);
 +    super.paintComponent(g);
  
      if (restart)
      {
@@@ -257,6 -259,7 +257,7 @@@
    public void dispose()
    {
      dispose = true;
+     od = null;
      synchronized (this)
      {
        restart = true;