I'm trying to get this to work with the 4.0 beta release.
I display a panel with closable set to true.
Click the close button and the panel disappears.
So far, so good.
Now I want to be able to bring the panel back -- AND have it be closable again. The showcase suggests that the panel be made to reappear by setting its closable to false. That works, but then the close button is gone and there is no obvious way to get it back.
You might want to re-consider if you want a panel or an ace:dialog?
However, you can always use the js show() fn on the widgetVar:-
<ace:panel header="SOME HEADER" id="pan1"
<ace:ajax event="close" /> <!-- if you need it -->