Re: Display problems with 'before-string in overlay

[Eli Zaretskii]

> From: Chong Yidong <address@hidden>
> Date: Wed, 11 Apr 2007 13:46:37 -0400
> Cc: address@hidden
> 
> "Lennart Borgman (gmail)" <address@hidden> writes:
> 
> > I want to put an overlay at the top of a buffer and display several
> > lines of text there. I use an overlay of length 1 at point 1 with a
> > before-string property to do this... the cursor is displayed at the
> > end of the first line of the 'before-string.
> >
> > [Modified test function]:
> >
> > (defun foo ()
> >   (interactive)
> >   (let ((o (make-overlay 1 1))
> >         (s (propertize "A string\nwith several rows\nat top\n"
> >                        'face 'highlight)))
> >     (overlay-put o 'before-string s)))
> 
> This buglet appears to be due to the following change:
> 
> 2005-07-13  Kim F. Storm  <address@hidden>
> 
>       * xdisp.c (cursor_row_p): Row is ok if cursor is at newline
>       from string, but string starts on this line (so we always
>       position cursor at start of string).
> 
> The relevant code is at xdisp.c:15861:
> 
>   if (PT == MATRIX_ROW_END_CHARPOS (row))
>     {
>       /* If the row ends with a newline from a string, we don't want
>          the cursor there, but we still want it at the start of the
>          string if the string starts in this row.
>          If the row is continued it doesn't end in a newline.  */
>       if (CHARPOS (row->end.string_pos) >= 0)
>         cursor_row_p = (row->continued_p
>                         || PT >= MATRIX_ROW_START_CHARPOS (row));
> 
> Changing this last line to `cursor_row_p = row->continued_p;', as it
> was before, eliminates the bug.  I haven't thought about how to fix
> this, though.

FWIW, I wouldn't touch this so close to the release: if no one noticed
this since July 2005, it's hardly a grave bug.