NullPointerException X11FontMetrics.stringWidth() causes Swing repaint to stop

Name: rk38400 Date: 04/20/98


We have some applications with JButtons using tool tips.
Sometimes when selecting the buttons we see the following
exception:

java.lang.NullPointerException
at sun.awt.motif.X11FontMetrics.stringWidth(X11FontMetrics.java:167)
at com.sun.java.swing.plaf.basic.BasicToolTipUI.getPreferredSize(BasicToolTipUI.java:102)
at com.sun.java.swing.JComponent.getPreferredSize(JComponent.java:705)
at com.sun.java.swing.ToolTipManager.showTipWindow(ToolTipManager.java:113)
at com.sun.java.swing.ToolTipManager$insideTimerAction.actionPerformed(ToolTipManager.java:326)
at com.sun.java.swing.Timer.fireActionPerformed(Timer.java:124)
at com.sun.java.swing.Timer$DummyComponent.processEvent(Timer.java:309)
at com.sun.java.swing.Timer$DummyComponent.fireEvent(Timer.java:315)
at com.sun.java.swing.Timer.fire(Timer.java:289)
at com.sun.java.swing.TimerQueue$TimerPanel.update(TimerQueue.java:367)
at java.awt.Component.dispatchEventImpl(Component.java:1725)
at java.awt.Container.dispatchEventImpl(Container.java:939)
at java.awt.Component.dispatchEvent(Component.java:1704)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:63)

Most importantly, after we see this exception we see problems with repaint of Swing "widgets". For
example, if you select an item in the table, it doesn't become
visibly selected unless you do something to force a repaint, such as
miniminizing/maximizing the frame. The same is true if you select a node in
the tree, or select a menubar item. In the latter case the menu does not appear
unless you minimize/maximize or do something else to force the repaint.

This appears to be timing related. The selection of the JButton should cancel the
tooltip timer, but apparently there is a window small enough where the timer is
expiring just as the button is being selected.
(Review ID: 28352)
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