Returns the background pattern. The default value is <code>null</code>.
@return the receiver's background pattern
@exception SWTException <ul> <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> </ul>
@see Pattern
@since 3.1
See Implementation
Returns the background pattern. The default value is <code>null</code>.
@return the receiver's background pattern
@exception SWTException <ul> <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> </ul>
@see Pattern
@since 3.1