Center window in GNOME

center_window.sh

#!/bin/bash
#
# Center a GNOME window, given its title. All windows with the given title are
# moved to the center of their respective displays.
#
# Example:
#
#     bash center_window.sh "foo.png - image editor"
#

run_javascript() {
    gdbus call -e -d org.gnome.Shell -o /org/gnome/Shell -m org.gnome.Shell.Eval "$1"
}

target_title="$1"

script=$(cat <<EOF
(function(target_title) {
    let num_moved = 0;
    const actors = global.get_window_actors();
    for (let i = 0; i < actors.length; i++) {
        const window = actors[i].get_meta_window();
        if (window.get_title() == target_title) {
            const display = window.get_display();
            const [dw, dh] = display.get_size();
            const frame = window.get_frame_rect();
            const x = (dw - frame.width) / 2;
            const y = (dh - frame.height) / 2;
            window.move_frame(0, x, y);
            num_moved += 1;
        }
    }
    return "moved " + num_moved + " windows.";
})
EOF
)

run_javascript "$script"\("\"$target_title\""\)