Gtk.Window.prototype.begin_resize_drag

function begin_resize_drag(edge:Gdk.WindowEdge, button:Number, root_x:Number, root_y:Number, timestamp:guint32):void {
    // Gjs wrapper for gtk_window_begin_resize_drag()
}

Starts resizing a window. This function is used if an application has window resizing controls. When GDK can support it, the resize will be done using the standard mechanism for the <link linkend="gtk-X11-arch">window manager</link> or windowing system. Otherwise, GDK will try to emulate window resizing, potentially not all that well, depending on the windowing system.

edge: position of the resize control
button: mouse button that initiated the drag
root_x: X position where the user clicked to initiate the drag, in root window coordinates
root_y: Y position where the user clicked to initiate the drag
timestamp: timestamp from the click event that initiated the drag