Re: try_cursor_movement not called?

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Wed, 01 Dec 2021 20:39:26 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Po Lu <luangruo@yahoo.com>
> >> Cc: emacs-devel@gnu.org
> >> Date: Wed, 01 Dec 2021 20:07:01 +0800
> >> 
> >> Thanks.  One other question: is it valid to assume w->window_start_valid
> >> is true inside redisplay_internal?
> >
> > There's no such member.  Did you mean window_end_valid, perhaps?
> 
> Yes I did, sorry for the confusion.

No, you cannot make that assumption.  window_end_valid becomes true
only if the window was successfully redisplayed and redrawn on the
glass.  If redisplay was interrupted (e.g., by new input that needs to
be processed), or we retry displaying a window after some unsuccessful
attempt, that flag will be false.

You will see that various parts of the display code test whether the
flag is true before attempting some optimizations, which should be a
clear sign that the flag could be false.