Re: "Final" version of tty child frames

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: martin rudalics <rudalics@gmx.at>,  jared@finder.org,  emacs-devel@gnu.org
> Date: Thu, 16 Jan 2025 13:15:48 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: martin rudalics <rudalics@gmx.at>
> >> 
> >> I now subtract 1 from the w->cursor.hpos if glyph->charpos is larger
> >> than PT
> >
> > This assumes unidirectional text, doesn't it?  The glyph whose charpos
> > is <= PT could well be to the right, not to the left.  In the brave
> > new world of bidirectional display, character positions change
> > non-linearly with screen positions.
> 
> We need only a suitable hpos/x though that is in the child frame.
> That should make the cursor magic in dispnew.c work that prevents
> cursors from "shining through child frames". Don't know what that means
> for R2L though.

"Suitable" in what way?  What is proposed here is to have an hpos
whose relation to charpos is indeterminate.  I'm not sure this will
fly.  AFAIU, we don't even understand well enough how come it fixed
the problem, do we?