Re: [Emacs-diffs] master bc0b340: A better fix for bug#21739

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Cc: Eli Zaretskii <address@hidden>
> Date: Sat, 24 Oct 2015 10:00:43 -0400
> 
> >     * src/buffer.c (set_update_modelines_for_buf): New function.
> >     (Fkill_buffer): Use it to set the global variable
> >     update_mode_lines if the killed buffer was displayed in some
> >     window.  Don't set windows_or_buffers_changed.  This is a better
> >     fix for bug#21739 than the previous fix, since it will cause only
> >     redisplay of mode lines, not of entire windows, but will still
> >     catch attention of x_consider_frame_title in xdisp.c, which
> >     redraws the frame title.
> 
> Same question as before: why isn't this caught when the window->buffer
> is changed?

Because changing a window's buffer only affects that single window.
How's that code to know the frame should be affected?