Checks taking literally hours; add a timeout?

[simoncozens]

Fonts are getting more and more complex; things like Handjet, for example, have thousands of points and hundreds of masters.

We have a number of checks which decompile and recompile fonts (such as hinting_stats and varfont/generate_static) which take a ridiculously long time on Handjet; another check, interpolation_issues, takes 11 hours on this font (I counted).

The annoying thing is that these checks are not something we can optimise in Fontbakery; the underlying operations are all FontTools routines: ttFont.save(), mutator.instantiateVariableFont() and varLib.interpolatable.test.

Of course this is a pathological font, but we want to be able to deal with arbitrary fonts. It's no good if you throw a directory of fonts at fontbakery and come back six hours later to discover that your CI job has died and you got no output. I figure our options are:

1. Replace these particular checks with Rust equivalents, or
2. Add a timeout for each check.

I think (2) is possible but it would probably involve messing around with signal handlers and I don't know how well that would play with -j (and Windows). It's probably the lowest cost approach in the short term, but fonts will only get more complicated, and we will have to do (1) eventually.

[davelab6]

Can't we just add a timeout to fb itself and run it per family, rather than at a directory of many families, in such a case? Or just have a warning when the list of fonts fed to the main process is larger than 18?

[behdad]

I can take a look and see if the interpolatable algorithms can be sped up. But yeah if someone's up to porting that to Rust that would be even better.

[behdad]

I can take a look and see if the interpolatable algorithms can be sped up. But yeah if someone's up to porting that to Rust that would be even better.

I can fix that fairly easily. Need to shuffle some code around. Only one of the glyphs (pixel) has variations (over 100 masters). The other glyphs have only one master. No need to instantiate and test them all at all the over-100 master locations for the font.

[behdad]

Fix up in fonttools/fonttools#3300

[simoncozens]

That fixes the interpolation errors check, but the other two are still very slow.

[behdad]

Can you tell how long the other two take? I'll take a look at speeding up saving if possible.

[simoncozens]

Saving the font after it's decompiled takes 25 seconds:

>>> start = timer() ; font.save("foo.ttf"); end = timer(); print(end-start)
24.827587366104126

Instantiating takes 48s

$ time fonttools varLib.instancer Handjet\[ELGR,ELSH,wght\].ttf wght=400
Restricting axes: {'wght': (400, 400, 400)}
Loading variable font
Restricted limits: {'wght': (400, 400, 400)}
Normalized limits: {'wght': (0, 0, 0, 300, 500)}
Instantiating glyf/gvar tables
Instantiating HVAR table
Instantiating STAT table
Instantiating fvar table
Pruning name table
Saving partial variable font Handjet[ELGR,ELSH,wght]-partial.ttf
fonttools varLib.instancer Handjet\[ELGR,ELSH,wght\].ttf wght=400  48.51s user 0.18s system 99% cpu 48.820 total

[behdad]

Saving the font after it's decompiled takes 25 seconds:

PR for speeding up saving: fonttools/fonttools#3301

For me, brings it down from 11s to 0.22s.

[behdad]

Instantiating takes 48s

Same PR (fonttools/fonttools#3301) brings down instancing speed for me from 23s down to 0.36s.

[yisibl]

Any plans to rewrite fontbakery using Rust?

[simoncozens]

Plans, no. Experiments, certainly. ;-)

[simoncozens]

This is all better now.