Cast as fn pointer to fix build error
Cast as fn pointer to fix build error

gkoz/gtk-rs-gtk,LordSentox/gtk,nicokoch/glib,daa84/gtk,gkoz/rust-gnome-glib,rust-gnome/gtk,gkoz/gtk-rs-gtk,drewet/gtk,Susurrus/gtk,gkoz/rust-gnome-gtk,EPashkin/rust-gnome-gtk,rust-gnome/gtk,rust-gnome/cairo,mitaa/gtk,gkoz/rust-gnome-cairo,mitaa/gtk,Susurrus/glib,insanebits/gtk,EPashkin/rust-gnome-gtk,Susurrus/gtk,gkoz/gtk-rs-glib,rust-gnome/glib,drewet/gtk,insanebits/gtk,gkoz/gtk-rs-pango,EPashkin/rust-gnome-glib,gkoz/gtk-rs-cairo,daa84/gtk,LordSentox/gtk,gkoz/rust-gnome-gtk,rtsuk/cairo