Opsz bug in Firefox

[guidoferreyra]

Hi!
I’ve found an odd issue when setting Fraunces to the max value for opsz and a font size greater than 256px. When these conditions are matched It doesn‘t renders the correct font variation.
In the screenshot below you can see two lines.
Both uses the same font variation settings but different font files. The top line uses the current font files from the "fonts" folder of this repo and the bottom line, that is working as expected, uses a font file from the Fraunces Minisite.

From Left to Right: Chrome, Safari, Firefox.

Probably it‘s a FF bug but I couldn’t reproduce this error with other fonts that has opsz too.
Here I attach the test html so you can see this by yourselves.

FrauncesTestCase.zip

Best.

[davelab6]

I can reproduce this in Firefox stable, but not in Firefox Nightly:

I am curious why this is happening, though. I guess a careful comparison of an opsz font that does not do this using a tool like https://github.com/googlefonts/fontdiffenator or https://github.com/source-foundry/fdiff or OTMaster could uncover what is happening...

[davelab6]

This seems to happen only in Fraunces, so I would like this to be debugged and fixed by Viviana or someone else :)

[guidoferreyra]

Hi! I have a possible solution that seems to fix this issue but I didn‘t tested if it cause something unwanted in other areas. I can make a PR later if no one is already working on this.

[davelab6]

PR would be great, or just an explanation :)

[guidoferreyra]

I changed the default value for opsz to match the min value and rebuilt the fonts.

[davelab6]

I'm curious what the TTX diff is for the fvar table, eg

ttx -t fvar old.ttf;
ttx -t fvar new.ttf;
diff old.ttx new.ttx;

[guidoferreyra]

That was exactly what I’ve done to know why the minisite version was working fine.
Between the version I modified and the one from the repo the only difference is that. And some comments in the named insntances.

11c11
<       <DefaultValue>144.0</DefaultValue>
---
>       <DefaultValue>9.0</DefaultValue>
478c478
<     <!-- 144pt S100 Thin -->
---
>     <!-- Thin -->
487c487
<     <!-- 144pt S100 Light -->
---
>     <!-- Light -->
496c496
<     <!-- 144pt S100 Regular -->
---
>     <!-- Regular -->
505c505
<     <!-- 144pt S100 SemiBold -->
---
>     <!-- SemiBold -->
514c514
<     <!-- 144pt S100 Bold -->
---
>     <!-- Bold -->
523c523
<     <!-- 144pt S100 Black -->
---
>     <!-- Black -->

[vv-monsalve]

I changed the default value for opsz to match the min value and rebuilt the fonts.

Thanks, Guido. It was solved here