Throws an <code>SWTException</code> if the receiver can not
be accessed by the caller. This may include both checks on
the state of the receiver and more generally on the entire
execution context. This method <em>should</em> be called by
widget implementors to enforce the standard SWT invariants.
<p>
Currently, it is an error to invoke any method (other than
<code>isDisposed()</code>) on a widget that has had its
<code>dispose()</code> method called. It is also an error
to call widget methods from any thread that is different
from the thread that created the widget.
</p><p>
In future releases of SWT, there may be more or fewer error
checks and exceptions may be thrown for different reasons.
</p>
@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>
Throws an <code>SWTException</code> if the receiver can not be accessed by the caller. This may include both checks on the state of the receiver and more generally on the entire execution context. This method <em>should</em> be called by widget implementors to enforce the standard SWT invariants. <p> Currently, it is an error to invoke any method (other than <code>isDisposed()</code>) on a widget that has had its <code>dispose()</code> method called. It is also an error to call widget methods from any thread that is different from the thread that created the widget. </p><p> In future releases of SWT, there may be more or fewer error checks and exceptions may be thrown for different reasons. </p>
@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>