Re: Emacs defeats ClearType

[jasonr]

Quoting David Abrahams <address@hidden>:

> Incidentally, it seemed to work just fine for me if I remove the
> checks for whether cleartype is enabled altogether, and just make the
> width adjustments unconditionally.

That is not a good idea. Your patch potentially affects performance, since it
tells lies about the width of characters to counteract the system's lies, and
may make them appear to be wider than their bounding box when they are not. If
a character being redisplayed is detected to be wider than its bounding box,
then the next character needs to be redrawn also, possibly cascading out to the
full line in the worst cases. So we should only tell these lies when we know the
system could be lying.

What would be better is to do the test for Cleartype once per font and cache the
result. Actually, you use a system setting for the test, so if there is not a
way to find out if Cleartype is used for a specific font (I think there is),
then a single test at startup is all that will be needed.