Use-case when positioning a window is necessary

[David Edmundson]

>And that is where positioning is necessary: to not occlude the line of
text where the cursor is, and to show the documentation at a sensible
place (near the cursor position).

xdg-foreign will just get that window on top. You don't have any
control of where on top it is, merely a child-parent relationship
It will occlude or be nowhere near the cursor. xdg-foreign alone won't
be a complete solution.

David