GtkPaned::set_position
void set_position(int position);
set_position() sets the
position of the dividing handle at the specified number of pixels
from the edge of the widget, in the direction of the pane arrangement,
without regard to the size requests of the child widgets in the panes.
It is overridden by the user's repositioning of the dividing handle.
To unset the position of the dividing handle, use