can-close?

Called just before the window might be closed (e.g., by the window manager). If #f is returned, the window is not closed, otherwise on-close is called and the window is closed (i.e., the window is hidden, like calling show with #f).

This method is not called by show .

• (send a-frame:file-mixin can-close?) -> boolean

  Checks to see if the editor has been saved.