Re: Display performance degradation

[Eli Zaretskii]

> Date: Sat, 02 Jan 2010 12:05:12 +0100
> From: Jan_Djärv <address@hidden>
> Cc: address@hidden, address@hidden
> 
> It seems to me that lookup_named_face always merges the face with
> the default face.

Well, it must, mustn't it?  A face specification does not need to be
complete; it is expected that the unspecified attributes are inherited
from the default face.

The initial issue was why lookup_named_face is at all called, if no
faces were encountered while scanning buffer text to be displayed.
But I think I know the answer: Emacs needs a fully specified face to
look it up in the face cache.  Technically, this is because the cache
lookup is by face attributes, but there's probably a deeper reason
for this design.

Anyway, is the call to lookup_named_face expensive, for all the calls
but the first one which use the same face symbol?  If it is cheap,
then perhaps this is a non-issue.