Sets the area of the receiver which can be changed
by drawing operations to the rectangular area specified
by the argument. Specifying <code>null</code> for the
rectangle reverts the receiver's clipping area to its
original value.
@param rect the clipping rectangle or <code>null</code>
@exception SWTException <ul>
<li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
</ul>
Sets the area of the receiver which can be changed by drawing operations to the rectangular area specified by the argument. Specifying <code>null</code> for the rectangle reverts the receiver's clipping area to its original value.
@param rect the clipping rectangle or <code>null</code>
@exception SWTException <ul> <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> </ul>