[cairo] cairo-pdf glyph positioning bug with librsvg

Emmanuel Pacaud emmanuel.pacaud at lapp.in2p3.fr
Fri Feb 22 14:39:05 PST 2008


Le jeudi 21 février 2008 à 20:42 -0500, Behdad Esfahbod a écrit :
> > >   - librsvg also was using the ink extents in some places where logical
> > > extents should be used.  Fixed in the patch.
> > 
> > That's something I'm interrested in. I'm currently implementing a
> > pango/cairo based mathml renderer, and I'm not really confident in my
> > use of the pango API. I guess I've not fully understood the difference
> > between logical and ink extents, and how to use them when you have to
> > manually position several pango layout in a single row. The pango
> > documentation lacks some explanation regarding extents.
> I've wanted to fix the docs for a while, here is where to follow:
>   http://bugzilla.gnome.org/show_bug.cgi?id=347009
> In short, think of ink extents as cairo path extents, the tight bounding
> box of all the ink involved.  Logical extents on the other hand are the
> logical boundary.  A space character for example has 0,0,0,0 ink rect,
> but its logical extents have a width of a single space, and the
> ascent/decent of the current font.  Hope that helps.

It does, a bit...

> Re MathML rendering, I'm interested to hear more about it.

I've just put the repository on
people.freedesktop.org/~emmanuel/gmathml.git. It should appear on
cgit.freedesktop.org soon.

Don't expect too much yet. My goal is to develop a glib/cairo/pango
based mathml renderer, with a DOM like API. I've started this project
initially as a vala experiment, but finally switched to plain C (I still
think vala is an interesting idea, but the lack of documentation and the
bugs I've encountered, even if promptly fixed, were too much annoying).

>   There's this
> new OpenType MATH table that should help with positioning.  I have plans
> to include that in HarfBuzz at some point.  Having a user lined up
> helps :).  

I've googled a bit, but didn't find any interesting information
regarding this math table. Do you have some pointers ?

> Gecko uses pango to render MathML already, and I think there
> a GTK+ widget floating around the net too.

I guess it's gtkmathview. I'm not sure it uses pango though.


Emmanuel PACAUD
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