[cairo] Cairo/FreeType integration [Advanced]

[Ian Britten]

Behdad Esfahbod wrote:
>>    I'm uncertain if the FT_Face I give you connects back to our
>>    FT_Library (and driver), or if you'll end up using your own
>>    instance (without our driver), meaning you'd be unable to get the
>>    correct FT_Glyph.
> 
> If you provide cairo with your FT_Face, we use the library from that.
> Simply use cairo_ft_font_face_create_for_ft_face() and it should all
> work.

Phew!  Many thanks for confirming this!  I hadn't traced through the
various FT data structures to determine this.
On to coding then...   :)

> Right, but a FreeType+ICU combo need not do any rasterization to begin
> with.  You can do all your shaping with ICU and feed cairo with glyph
> indices.  It would be better if you ask cairo for glyph metrics, but
> that's not a huge deal.

Hmmm... That's twice you've mentioned that now, so I guess I should
maybe pursue this point a bit more...
[ I'm sure you can understand my hesitation to disturb our existing,
stable, tested solution, without knowing *why* ... ]

So, why would it be "better" to use Cairo for glyph metrics?
Accuracy?  Performance?  Other?

As always, thanks for any information. (And your patience! :) )
Ian