Re: Latest changes in redisplay code

[Dmitry Antipov]

On 02/05/2013 10:01 PM, Eli Zaretskii wrote:

> In any case, the potential for problems is still there, because now
> w->base_line_pos gets reset to zero in many more places than it was
> before.  Previously, only xdisp.c would manipulate this attribute in a
> few well-defined places.  Now it can be reset by any function that
> calls adjust_window_count, including wset_buffer, which is called from
> many primitives, most of them outside xdisp.c.  Therefore, it's quite
> possible that we will now have to count from the beginning of the
> buffer much more frequently than we did before.  In large buffers,
> this could be quite a hit.

Hm. I'll try to reproduce such a situation and check what happens.
Maybe we should invalidate window_end_valid and base_line_pos only
if either window is really switched to another buffer or buffer
is changed.

> > > Revision 111584 also has a suspicious change:
> > >
> > >     @@ -3189,7 +3182,7 @@ set_window_buffer (Lisp_Object window, L
> > >        wset_window_end_pos (w, make_number (0));
> > >        wset_window_end_vpos (w, make_number (0));
> > >        memset (&w->last_cursor, 0, sizeof w->last_cursor);
> > >     -  wset_window_end_valid (w, Qnil);
> > >     +
> > >
> > > Why was this setting dropped?

Because w->window_end_valid is invalidated in wset_buffer, which is
called by set_window_buffer.

> Btw, here's one more questionable change, from revision 111583:
>
>    @@ -13784,25 +13777,21 @@ mark_window_display_accurate (Lisp_Objec
>       for (; !NILP (window); window = w->next)
>         {
>          w = XWINDOW (window);
>    -      mark_window_display_accurate_1 (w, accurate_p);
>    -
>          if (!NILP (w->vchild))
>           mark_window_display_accurate (w->vchild, accurate_p);
>    -      if (!NILP (w->hchild))
>    +      else if (!NILP (w->hchild))
>           mark_window_display_accurate (w->hchild, accurate_p);
>    +      else if (BUFFERP (w->buffer))
>    +       mark_window_display_accurate_1 (w, accurate_p);
>
> Isn't it possible for a window to have both an hchild and a vchild?

No. This is documented in window.h and regularly used in window.c,
for example, in delete_all_child_windows.

Dmitry