How do you put a transparent screen over a GWT widget?

High level abstraction:

In GWT, I need to create some sort of GUI feedback to show that a widget is either selected and/or has a mouse hovering over it.

Medium level abstraction:

My plan is to place a colored-transparent-screen over the widget. Think of a physical box with stuff in it... and now p开发者_StackOverflow社区lace a piece of glass with some coloring over the box.

I don't really know where to start on creating this sort of effect. My best guess would be to embed the widget into some sort of GWT widget.

(The GWT Cell widgets have some nice highlight effects. I would like the "colored-transparent-screen" to look similar to the CellTable highlighting when you mouse over the specific cells... but instead of affecting a cell it will affect a widget)

Use case:

I will have a GWT grid. Each grid cell is a widget (each widget is a grid of grids... with a grid of grids).

I used FocusPanel and twiddled with the CSS to achieve what you are trying to do. Which I think would not be necessary if a widget already implements HasFocus - i.e., not necessary to use FocusPanel but still need to twiddle with CSS.