gtk:window-deiconify (window)

window -- a gtk:window widget

Asks to deiconify, for example, unminimize, the specified window. Note that you should not assume the window is definitely deiconified afterward, because other entities, for example, the user or window manager, could iconify it again before your code which assumes deiconification gets to run.

You can track iconification via the "window-state-event" signal on the gtk:widget object.