Bug 937 : Fix regression of commit 071bdd6ce9f8c41ccecdbf8bc74f276ccd7ff651 (which disables print if !isShowing())

Commit 071bdd6ce9f8c41ccecdbf8bc74f276ccd7ff651
uses 'isShowing' state to determine whether to display or not.

It also uses 'isShowing' instead of 'isVisible' for printing,
which is a regression, since not showing elements offscreen shall be able to be printed.