[gtktextview] Too slow on win32

[Tor Lillqvist <tml iki fi>]

Oleg Klimov writes:
 > It makes the widget almost unusable. Has anyone researched what are the
 > reasons? Any ideas?

There are a couple of obvious places in pangowin32 that will benefit
from straightforward optimisation and some caching. There is an open
bug report on this. It's just a matter of time (and priorities; first
make it work, then make it fast).

(Just between you and me ;-), you can make pangowin32 faster by
bypassing Uniscribe: Set the PANGO_WIN32_NO_UNISCRIBE environment
variable to some non-empty value. It will still work fine for Latin
(and Cyrillic) scripts, for instance. This hopefully won't be
necessary once the optimisations and caching are in place, and this
possibility probably should be removed then. We don't want to
envourage people to bypass one of the main features of Pango, the
ability to render complex scripts.)

--tml