Present this after having processed the PopupLayout rules.
If the popup was previously now showing, it will be showed, otherwise it will change position according to
After calling this function, the result should be handled in response to the [signal@GdkSurface:
GdkPopup:layout] signal being
emitted. The resulting popup position can be queried using [method@Gdk.Popup.get_position_x], [method@Gdk.Popup.get_position_y], and the
resulting size will be sent as parameters in the layout signal. Use [method@Gdk.Popup.get_rect_anchor] and [method@Gdk.Popup.get_surface_anchor]
to get the resulting anchors.
Presenting may fail, for example if the this is set to autohide and is immediately hidden upon being
presented. If presenting failed, the [signal@Gdk.Surface:
GdkPopup:layout] signal will not me emitted.
the `GdkPopup` to show
the unconstrained popup width to layout
the unconstrained popup height to layout
the `GdkPopupLayout` object used to layout
false if it failed to be presented, otherwise true.