Returns the receiver's alpha value. The alpha value
is between 0 (transparent) and 255 (opaque).
@return the alpha value
@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>
Returns the receiver's alpha value. The alpha value is between 0 (transparent) and 255 (opaque).
@return the alpha value
@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>
@since 3.4