[vcs-log] cache Selection in table to only calculate it when its changed

platform/vcs-log/impl/src/com/intellij/vcs/log/ui/frame/VcsLogGraphTable.java

@@ -93,6 +93,7 @@ public class VcsLogGraphTable extends JBTable implements DataProvider, CopyProvi
   @NotNull private final TableCellRenderer myDummyRenderer = new DefaultTableCellRenderer();
   @NotNull private final GraphCommitCellRender myGraphCommitCellRenderer;
   private boolean myColumnsSizeInitialized = false;
+  @Nullable private Selection mySelection = null;
 
   @NotNull private final Collection<VcsLogHighlighter> myHighlighters = ContainerUtil.newArrayList();
 
@@ -121,6 +122,8 @@ public class VcsLogGraphTable extends JBTable implements DataProvider, CopyProvi
     addMouseMotionListener(mouseAdapter);
     addMouseListener(mouseAdapter);
 
+    getSelectionModel().addListSelectionListener(new MyListSelectionListener());
+
     PopupHandler.installPopupHandler(this, VcsLogActionPlaces.POPUP_ACTION_GROUP, VcsLogActionPlaces.VCS_LOG_TABLE_PLACE);
     ScrollingUtil.installActions(this, false);
 
@@ -463,7 +466,8 @@ public class VcsLogGraphTable extends JBTable implements DataProvider, CopyProvi
 
   @NotNull
   public Selection getSelection() {
-    return new Selection(this);
+    if (mySelection == null) mySelection = new Selection(this);
+    return mySelection;
   }
 
   private static class Selection {
@@ -917,4 +921,11 @@ public class VcsLogGraphTable extends JBTable implements DataProvider, CopyProvi
       mouseInputListener.mouseMoved(convertMouseEvent(e));
     }
   }
+
+  private class MyListSelectionListener implements ListSelectionListener {
+    @Override
+    public void valueChanged(ListSelectionEvent e) {
+      mySelection = null;
+    }
+  }
 }