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.