gmessage(1) on Linux
The text e3cd9eddc96e, as Debian 8 (Jessie), Debian 7 (Wheezy) shipped it.
a GTK-based xmessage clone
Flags it lists
-
-bg -
-borderless -
-buttons -
-center -
-default -
-display -
-encoding -
-entry -
-entrytext -
-fg -
-file -
-fn -
-font -
-geometry -
-help -
-iconic -
-name -
-nearmouse -
-noescape -
-nofocus -
-ontop -
-print -
-sticky -
-timeout -
-title -
-version -
-wrap