FULL PRODUCT VERSION :
$ java -version
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
$ uname -a
Darwin scrappy.local 14.5.0 Darwin Kernel Version 14.5.0: Wed Jul 29 02:26:53 PDT 2015; root:xnu-2782.40.9~1/RELEASE_X86_64 x86_64


A DESCRIPTION OF THE PROBLEM :
When the JOptionPane option buttons need a bigger width than the message, the calculated width appears to be a bit too short; the left edge of the first button is truncated.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached program on a Mac; note that the left edge of the "1" button is truncated.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
All option buttons are fully visible.
ACTUAL -
The left edge of the first button ("1") is truncated.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.*;

public class OptionPane
{
  public static void main(final String[] args) throws Exception
  {
    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    //UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JOptionPane.showOptionDialog(frame,
                                 "JOptionPane",
                                 "JOptionPane",
                                 JOptionPane.INFORMATION_MESSAGE,
                                 JOptionPane.DEFAULT_OPTION,
                                 null,
                                 new String[]{"3","2","1"},
                                 null);
    System.exit(0);
  }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Make the message long enough to force a bigger overall width:

import javax.swing.*;

public class OptionPane
{
  public static void main(final String[] args) throws Exception
  {
    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    //UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JOptionPane.showOptionDialog(frame,
                                 "JOptionPane with a longer description...",
                                 "JOptionPane",
                                 JOptionPane.INFORMATION_MESSAGE,
                                 JOptionPane.DEFAULT_OPTION,
                                 null,
                                 new String[]{"3","2","1"},
                                 null);
    System.exit(0);
  }
}