Windows / font / text futures ...

Thorsten Behrens thb at
Thu Mar 3 23:43:25 UTC 2016

Hi Michael,

you write:
> 	Having looked at this heap; and worse - the two different heaps for
> Windows text rendering, and also the big pile of strange cross-platform
> issues with stacking diacritics, emojis etc. I'm pretty convinced that
> we cannot do a good job of consistent text shaping and/or rendering
> cross-platform while using the Windows font rendering infrastructure.
Yeah, I suppose. But that alone won't fix the kind of issues you show
in your ascii art - as long as so much low-level layouting is still
happening in Writer (dx arrays, kashida filling etc).

> 	While we could switch to DirectWrite on windows, which may solve some
> of our problems; this will be in itself disruptive.
Incidentally - why that?

> 	So - I believe that we should switch to using harfbuzz and freetype
> consistently everywhere. This would have the huge benefit of precise
> cross-platform font rendering and metric fidelity, give us a font and
> shaping stack that is fully introspectable, drop some legacy Windows API
> usage, and allow all development work and fixing on all platforms to
> share the same underlying code.
I think that promise cannot be kept. Let's evaluate the merit of
switching to some truly great floss libraries based on other aspects -
you're not even getting consistent floating point math between
different CPUs, let alone different operating systems...

> 	There will of course also be some corner-cases where we may simply not
> be able to replicate the tangled old layout behaviour - which is
> (anyway) inconsistent across platforms - but - I think this is a one-off
> risk that is well worth taking to get us to a fully consistent, Free
> Software rendering stack. It is interesting that Microsoft also used freetype
> for their Office / Mac rendering in the recent past =)
Oh - got some reference for that? Since I guess for most complaints
about layouting problems I hear about, it's the different between MSO
and LibreOffice, rather than between LibreOffice on different
platforms. ;)


-- Thorsten
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