retain user set window position after show the window again

[WAN Hing Wah <50191914 ee cityu edu hk>]

I use gtk_Widget_set_uposition to set the default window position when I
start the program,however I want to let user to drag the window to other
position after it.In my menu part I have a function which is used to show
and hide the gtk_window by gtk_widget_show and gtk_widget_hide
respectively.
However, after the window is hided and show again...the Window will
show at the position where gtk_widget_set_uposition is set.
However,I wanna maintain  what the user have drag the window to.What can I
do?