Created attachment 7713 Replace deprecated functions Patch replaces deprecated functions gdk_device_grab/gdk_device_ungrab. They are deprecated since Gtk 3.20, and this is the mininal version of Gtk (configure script), I think we should avoid using these functions.
This week I replaced those functions exactly as you did, but it breaks rectangle selection when not using a compositor. Go to Window Manager Tweaks -> Compositor, uncheck Enable display compositing and run xfce4-screenshooter -r, you get: (xfce4-screenshooter:21305): Gdk-CRITICAL **: 18:34:50.965: Window 0x5578fa668010 has not been made visible in GdkSeatGrabPrepareFunc
Done in: https://git.xfce.org/apps/xfce4-screenshooter/commit/?id=fbed501a246756dd122a105b07a5a483a875011c https://git.xfce.org/apps/xfce4-screenshooter/commit/?id=187d4ec91999d67db4490f6c3fc5283fb376f5b0