Re: Unicode normalization and text display differences

[Behdad Esfahbod <behdad esfahbod gmail com>]

On 16-01-06 03:07 PM, Benjamin Kiessling wrote:
> On 01/06, Behdad Esfahbod wrote:
> > On 16-01-06 02:55 PM, Benjamin Kiessling wrote:
> > > On 01/06, Behdad Esfahbod wrote:
> > > > Hi Ben,
> > > >
> > > > You at least need to tell us on what platform you are testing this and with
> > > > what fonts.
> > >
> > > Sorry, I'm running on Debian testing (libpango-1.0 package version
> > > 1.36.8-3) and using it through GObject introspection from python
> > > (although that's probably not the issue here). Apart from setting up the
> > > whole CairoSurface and Layout shebang the code boils down to
> > > set_font_description/set_text/show_layout.
> > >
> > > The font family used is GFS Philostratos, although the issue persists
> > > only with GFS fonts as I'm realizing just now. Using DejaVu Sans output
> > > is independent of normalization form. Is this to be expected? The
> > > documentation is mute about such points (and in general about how it's
> > > supposed to be used).
> >
> > It's probably the case that the GFS fonts don't support the combining marks,
> > and as such Pango picks them from a different font, which then breaks shaping.
>
> Makes sense. Is there a way to detect fallback, except disabling it
> completely using pango_attr_fallback_new() or instantiating a new
> fontconfig environment for a particular font?

If you care to walk the layout info using a layout iterator, you can check the
font used for each run of text, and under fallback, more than one font is used.