Re: Question about display engine

[Eli Zaretskii]

> Cc: Eli Zaretskii <address@hidden>, address@hidden
> From: martin rudalics <address@hidden>
> Date: Mon, 9 Sep 2019 09:39:13 +0200
> 
>  > I fixed that, try now please (it is in savannah already).
> 
> Thank you.  Works now as expected.
> 
> I'm still not convinced that it is a good idea to unconditionally run
> handle_face_prop_general from extend_face_to_end_of_line.  It will
> penalize processing every line shown in a window even if no attribute
> processed is affected by a nil :extend attribute.

The penalty is just a call to merge faces and look up the merged face
in the face cache (which, under most usual circumstances, will always
find an already realized face in the cache).  If you are worried about
face merging itself, then don't be: we do this in redisplay all the
time when displaying buffers, except in the most boring cases (like
buffer of all-ASCII text in Fundamental mode).

And the alternative is IMO worse: it will require tracking all the
face changes and deciding upon each change whether it does or doesn't
affect the line extension.