02-16-2011 08:22 AM
If you're talking about the actual button, you can set the "alpha" value. The value is between 0-1. 1 being opaque, and 0 being transparent. So 0.5 would be semi-transparent.
If you're talking about the icon placed in the button, then the icon image has to manage the transparent part of it. PNG-24 is a good format to save images as and allows for transparent parts.
02-16-2011 09:15 AM
In that case, you might have to create your own "RoundIconButton" control from Sprite or UIComponent. It is pretty easy. Just override the draw() method in UIComponent extended class to draw the round border and center the image and add the proper event listeners for mouse down and mouse up for click and change border color when selected. If you get stuck, I can post some code later today.