Re: Jumpy variations

Werner,

I completely misdiagnosed the problem. It is indeed the autohinter
that produces unpredictable advance and height in variable fonts.

Unhinted variable font, which falls back on the autohinter is
https://github.com/adobe-fonts/source-sans/tree/release/VF

A hinted VF is Roboto. Make sure to get the hinted version.
https://github.com/googlefonts/roboto-3-classic/releases

Alexei



On Tue, Aug 26, 2025 at 12:49=E2=80=AFPM Werner LEMBERG <[email protected]> wrote:
>
>
> >> Playing with ftmulti I noticed that almost all variable fonts
> >> exhibit jumpy heights and advances when varying individual axes,
> >> instead of monotonous changes. I could associate this weird
> >> behavior with the bytecode hinting. Without it or with autohining,
> >> the heights and advances are changing smoothly.
> >
> > The best way to see this behaviour is
> >
> > % ftgrid.exe -f6 ~/Fonts/Adobe/SourceSans3VF-Roman.ttf
>
> I couldn't find this font.  Link, please!  However, the font
> `SourceSans3-VariableFont_wght.ttf` (as downloaded from Google Fonts)
> doesn't contain any hints =E2=80=93 or rather, it contains a pseudo-prep =
table
> with a few instructions while `maxSizeOfInstructions` in the `maxp`
> table is incorrectly set to zero...
>
> > When you start increasing the weight [F4] the advance line wiggles.
>
> It would be interesting to see the behaviour with a font that contains
> real bytecode instructions...
>
>
>     Werner



--=20
Alexei A. Podtelezhnikov, PhD