[cairo] Possible bug in font hinting metrics?

Carl Worth cworth at cworth.org
Fri Sep 7 15:03:04 PDT 2007

On Fri, 7 Sep 2007 22:23:57 +0100, George Wright wrote:
> On Friday 07 September 2007 21:50:19 you wrote:
> > Are you using the scaled font with the scale included in the CTM?  You
> > should.
> Surely if you're rendering the font onto a scaled context it should
> automatically take care of that?

We talked about that when we added cairo_set_scaled_font, (previously,
you had to set the font face, options, etc. and just hope that it all
worked out to match exactly).

It was proposed that setting the font should force a change in the
matrix, but we decided that that could get too confusing, (when
reading code with an unexpected matrix change in it, it wouldn't be at
all obvious that the change was coming from cairo_set_scaled_font).

But, then again, it's not obvious to you when looking at your code
where the incorrect metrics are coming from, so...

Anyway, one other potentially interesting use case for the current
behavior, (as mentioned in the cairo_set_scaled_font documentation),
is that the scaling must match, but the translation can actually
differ. So just forcing the CTM from the font into the cairo_t would
prevent that as well.

Documentation improvements to cairo_set_scaled_font would be quite
welcome here.

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