Re: Display problems with 'before-string in overlay

[Lennart Borgman (gmail)]

Chong Yidong wrote:
> Richard Stallman <address@hidden> writes:
>
> >     At this stage of the release cycle, a grave bug is one that makes Emacs
> >     crash, or causes really bad redisplay behaviour.
> >
> > I think redisplay bugs are serious bugs.
>
> In this case, I know what the fix is (see attached patch).  The
> trouble is that it's a rather big change, and likely to cause
> problems, whereas the problem it corrects is not commonly encountered
> (cursor positioning in multi-line overlay before/after-strings).
>
> So I'd like to delay this till after Emacs 22.1.  WDYT?


Great. I will test this and I guess I do not have to say I want it now. 
I can of course not say I understand the code, but I will try to look at 
it anyway.


BTW when I made a brief try to understand the code I noticed the text 
property Qcomposition. That is missing from (info "(elisp) Special 
Properties"). Should it not be there? Or is it something internal only?


Another little question: On w32 I failed to apply this patch with the 
patch program from gnuwin32 (version 2.5.9). I wonder if this is a 
problem with that patch program or something else. How do I continue 
when patch fails?

Most of the patch where applied. The patch fails with the following 
reject (xdisp.c.rej):

***************
*** 11933,11952 ****
        Lisp_Object string;
        struct glyph *stop = glyph;
        int pos;

        limit = make_number (pt_old + 1);
        glyph = string_start;
        x = string_start_x;
        string = glyph->object;
!       pos = string_buffer_position (w, string, string_before_pos);
!       /* If STRING is from overlay, LAST_POS == 0.  We skip such glyphs
!        because we always put cursor after overlay strings.  */
!       while (pos == 0 && glyph < stop)
        {
          string = glyph->object;
          SKIP_GLYPHS (glyph, stop, x, EQ (glyph->object, string));
          if (glyph < stop)
!           pos = string_buffer_position (w, glyph->object, string_before_pos);
        }

        while (glyph < stop)
--- 11934,11955 ----
        Lisp_Object string;
        struct glyph *stop = glyph;
        int pos;
+       Lisp_Object overlay = Qnil;

        limit = make_number (pt_old + 1);
        glyph = string_start;
        x = string_start_x;
        string = glyph->object;
!       pos = string_buffer_position (w, string, string_before_pos, 
&overlay);
!       /* If STRING is from overlay, skip its glyphs because we always
!        put cursor after overlay strings.  */
!       while ((pos == 0 || !NILP (overlay)) && glyph < stop)
        {
          string = glyph->object;
          SKIP_GLYPHS (glyph, stop, x, EQ (glyph->object, string));
          if (glyph < stop)
!           pos = string_buffer_position (w, glyph->object,
!                                         string_before_pos, &overlay);
        }

        while (glyph < stop)
***************
*** 15858,15869 ****
    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));
        else if (MATRIX_ROW_ENDS_IN_MIDDLE_OF_CHAR_P (row))
        {
          /* If the row ends in middle of a real character,
--- 15861,15870 ----
    if (PT == MATRIX_ROW_END_CHARPOS (row))
      {
        /* If the row ends with a newline from a string, we don't want
!        the cursor there.
         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;
        else if (MATRIX_ROW_ENDS_IN_MIDDLE_OF_CHAR_P (row))
        {
          /* If the row ends in middle of a real character,