Re: "Final" version of tty child frames

[martin rudalics]

>> It's obvious that this _is_ a redisplay optimization trap.  But it's a
>> very sophisticated one because the cursor ends up at the correct end of
>> the line.  With other words C-f does what C-e does.
>
> I can suggest two things:

These don't help.  Meanwhile I suppose that it's not related to
optimizations.  What happens is:

I'm in a base (underlying, normal) frame which is partially covered by a
child frame.  With 'line-beginning-position' 686 and 'line-end-position'
759 and point at 724 I try to move point to position 725 which is the
first position on that row covered by the child frame.

In set_cursor_from_row at

  if (!((row->reversed_p ? glyph > glyphs_end : glyph < glyphs_end)
        && BUFFERP (glyph->object) && glyph->charpos == pt_old)
      && !(bpos_max <= pt_old && pt_old <= bpos_covered))

I have x = 39 which is the expected value 725 - 686 and I would like it.
But that check fails (or better "succeeds") because of

(gdb) p glyph->object
$104 = XIL(0)
(gdb) p glyph->charpos
$105 = -1
(gdb) p pt_old
$106 = 725
(gdb) p bpos_covered
$109 = 0

Then in

      else if ((row->truncated_on_right_p && pt_old > bpos_max)
               /* Zero-width characters produce no glyphs.  */
               || (!empty_line_p
                   && (row->reversed_p
                       ? glyph_after > glyphs_end
                       : glyph_after < glyphs_end)))
        {
          cursor = glyph_after;
          x = -1;
        }

I have

(gdb) p !empty_line_p
$111 = 1
(gdb) p glyph_after < glyphs_end
$110 = 1

x is set to -1 and in

  if (x < 0)
    {
      struct glyph *g;

      /* Need to compute x that corresponds to GLYPH.  */
      for (g = row->glyphs[TEXT_AREA], x = row->x; g < glyph; g++)
        {
          if (g >= row->glyphs[TEXT_AREA] + row->used[TEXT_AREA])
            emacs_abort ();
          x += g->pixel_width;
        }
    }

x eventually becomes 73 (759 - 686) which is what I see.  What could I
do to make the check at the top succeed?

martin