Gets the height of one item.
<p>
This operation will fail if the height of
one item could not be queried from the OS.
@return the height of one item in the widget
@exception SWTException <ul>
<li>ERROR_THREAD_INVALID_ACCESS when called from the wrong thread
<li>ERROR_WIDGET_DISPOSED when the widget has been disposed
</ul>
Gets the height of one item. <p> This operation will fail if the height of one item could not be queried from the OS.
@return the height of one item in the widget
@exception SWTException <ul> <li>ERROR_THREAD_INVALID_ACCESS when called from the wrong thread <li>ERROR_WIDGET_DISPOSED when the widget has been disposed </ul>