Called by widgets as the user moves around the window using keyboard shortcuts.
direction argument indicates what kind of motion is taking place (up, down, left, right, tab forward, tab backward).
This function calls the [vfunc@Gtk.Widget.focus] virtual function; widgets can override the virtual function in order to implement appropriate focus behavior.
The default `focus()` virtual function for a widget should return `TRUE` if moving in
direction left the focus on a focusable
location inside that widget, and `FALSE` if moving in
direction moved the focus outside the widget. When returning `TRUE`, widgets
normally call [method@Gtk.Widget.grab_focus] to place the focus accordingly; when returning `FALSE`, they don’t modify the current focus
This function is used by custom widget implementations; if you're writing an app, you’d use [method@Gtk.Widget.grab_focus] to move the focus to a particular widget.
direction of focus movement
true if focus ended up inside this