Re: Analysis of redisplay performance on Windows

[YAMAMOTO Mitsuharu]

>>>>> On Sun, 27 Jul 2008 22:53:47 +0100, Jason Rumney <address@hidden> said:

> One difference between Emacs 22 and 23 is that we compute glyph
> indexes properly in Emacs 23, while on 22 we use unicode code
> points. Since we call font->encode_char once per character rather
> than for a whole run, the overhead of selecting fonts into the GC is
> multiplied.

According to the document below, Uniscribe seems to provide some
mechanism to defer heavy operations such as get_frame_dc and
SelectObject.

  
http://www.microsoft.com/typography/developers/uniscribe/uniscribe.htm#SCRIPT_CACHE

I'm not sure if this retrying with E_PENDING solves the performance
problem on Windows with Uniscribe.  But I think it's worth trying
before resorting to platform-independent changes because the
performance problem is not found so far in other platforms including
my local Core Text font-backend driver mentioned in
http://lists.gnu.org/archive/html/emacs-devel/2008-02/msg02186.html.

                                     YAMAMOTO Mitsuharu
                                address@hidden