FLEX: popupManager: TitleWindow: how to make the background transparent

I'm using PopupManager to display (开发者_JAVA技巧not modal) popups in Flex.

How can I make the background of my TitleWindow popup completely transparent? Now it is semi-transparent.. see picture with semi-transparent background (i.e. I just want the label inside visible):

http://dl.dropbox.com/u/72686/semiTransparent.png

Maybe, instead of making it transparent I could try to reduce the padding, in order to make only the children visible ?

thanks

If you want to make it transparent, add

borderAlpha="0.0"

If you also want to remove the side and bottom borders completely, add

borderThicknessLeft="0" borderThicknessRight="0"

You can't remove the header, even thought there is borderThicknessTop option.
Also, the borderThickness="0" option doesn't work as far as I know.

Set the backgroundAlpha style of the TitleWindow to 0.

Edit, oops, my mistake, since it's a subclass of Panel, you'll also need to set the borderAlpha style to 0 as well. If you're using the default flex skins, the white arrow is the "background" and the blue area is the "border".