Window.deiconify

void deiconify()

Asks to deiconify (i.e. unminimize) the specified window. Note that you shouldn’t assume the window is definitely deiconified afterward, because other entities (e.g. the user or [window manager][gtk-X11-arch])) could iconify it again before your code which assumes deiconification gets to run.

You can track iconification via the “window-state-event” signal on #GtkWidget.