FULL PRODUCT VERSION :
Microsoft Windows [Version 6.3.9600]
(c) 2013 Microsoft Corporation. All rights reserved.

C:\Users\Owner>java -version
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)

C:\Users\Owner>

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.3.9600]
(c) 2013 Microsoft Corporation. All rights reserved.

C:\Users\Owner>ver

Microsoft Windows [Version 6.3.9600]

C:\Users\Owner>

A DESCRIPTION OF THE PROBLEM :
Using the Windows classic look and feel with JInternalFrame has title bar buttons with incorrect widths as can be seen in the following screenshot:
http://i.imgur.com/XZGEUrY.png

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create a JInternalFrame and set the Windows classic look and feel.


REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Setting the property manually will fix it temporarily:
UIManager.put("InternalFrame.titleButtonWidth", 20);

SUPPORT :
YES