Sets the direction in which the menu will be popped up, as
well as changing the arrow's direction. The child will not
be changed to an arrow if it was customized.
If the menu when popped out would have collided with screen edges,
we will do our best to keep it inside the screen and fully visible.
If you pass GTK_ARROW_NONE for a direction, the menu will behave
as if you passed GTK_ARROW_DOWN (although you won't see any arrows).
Sets the direction in which the menu will be popped up, as well as changing the arrow's direction. The child will not be changed to an arrow if it was customized. If the menu when popped out would have collided with screen edges, we will do our best to keep it inside the screen and fully visible. If you pass GTK_ARROW_NONE for a direction, the menu will behave as if you passed GTK_ARROW_DOWN (although you won't see any arrows).