Sets the receiver's alpha value which must be
between 0 (transparent) and 255 (opaque).
<p>
This operation requires the operating system's advanced
graphics subsystem which may not be available on some
platforms.
</p>
@param alpha the alpha value
@exception SWTException <ul>
<li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
<li>ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available</li>
</ul>
Sets the receiver's alpha value which must be between 0 (transparent) and 255 (opaque). <p> This operation requires the operating system's advanced graphics subsystem which may not be available on some platforms. </p> @param alpha the alpha value
@exception SWTException <ul> <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> <li>ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available</li> </ul>
@see #getAdvanced @see #setAdvanced
@since 3.1