Sets the receiver's tool tip text to the argument, which
may be null indicating that no tool tip text should be shown.
@param str the new tool tip text (or null)
@exception SWTException <ul>
<li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
<li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
</ul>
Sets the receiver's tool tip text to the argument, which may be null indicating that no tool tip text should be shown.
@param str the new tool tip text (or null)
@exception SWTException <ul> <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> </ul>