Obtains the location of the mouse pointer in widget coordinates.
Widget coordinates are a bit odd; for historical reasons, they are
defined as widget->window coordinates for widgets that are not
GTK_NO_WINDOW widgets, and are relative to widget->allocation.x,
widget->allocation.y for widgets that are GTK_NO_WINDOW widgets.
Obtains the location of the mouse pointer in widget coordinates. Widget coordinates are a bit odd; for historical reasons, they are defined as widget->window coordinates for widgets that are not GTK_NO_WINDOW widgets, and are relative to widget->allocation.x, widget->allocation.y for widgets that are GTK_NO_WINDOW widgets.