[cairo] Rounding bug in cairo_ft_font.c

[Carl Worth]

At Sat, 08 Jan 2005 22:49:03 -0500, Owen Taylor wrote:
> On Sat, 2005-01-08 at 17:15 -0800, Keith Packard wrote:
> > This is a minor part of a larger patch that I have here which tries to
> > resolve the metrics issue of transformed fonts.  I'm still not happy with
> > the result.  I think PostScript's answer might be a better long-term plan.
> > In that world, metrics are always returned in 'font space', that pre-scaled
> > world before the affine font and ctm transforms are applied.  
> 
> But even given device-adjustment, the font space convention doesn't
> sound very convenient. If I'm trying to align some text, I want to
> know how big it is in user space.

That's the feeling I've had in this regard, but I haven't yet looked
into all of the issues in detail.

The convention that "all numbers crossing the API are in user-space[*]"

is very appealing and I don't want to give it up unless we really
don't have another option. I'm certainly willing to turn some scalars
into vectors for example. Things like "x+x_height, y+y_height" are not
much harder than "x, y+height", but transforming from font space to
user-space seems an awkward burden on the user.

But, I'll try to inform myself a bit better on the other issues that
are in play here.

-Carl

[*] The only exceptions I'm aware of are the inverse_transform
functions which take device-space coordinates for obvious reasons.
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