Re: The unwarranted scrolling assumption

[Eli Zaretskii]

> From: Lennart Borgman <address@hidden>
> Date: Fri, 18 Jun 2010 15:56:38 +0200
> Cc: address@hidden, address@hidden, address@hidden
> 
> Can you please explain why window_end_valid flag should be involved?

This flag indicates that the redisplay finished and the current glyph
matrix is up to date.  It is imperative to know that, because
try_scrolling, the function you are trying to get called, reuses
portions of the current glyph matrix (to avoid redrawing the entire
window).  It is unsafe to reuse the current matrix if it is not
guaranteed to be up to date.

> Can you please also comment on the point where to check if clipping
> has changed? Is not the entry of redisplay_window the right point for
> this?

What do you mean by ``where to check if clipping has changed''?  The
clip_changed flag is checked in many places during redisplay.