Custom profile development

[clauseggers]

So it turn out I need more than just a list of existing things to turn on or off, so I gather that is beyond the TOML file and sends me into a Rust module? Say if I wanted to make a check of my metadata, how would I construct such a module external to the Fontspector repo? Can that even be explained in a few sentences? I would like my custom profile to be in my own repo, and then use that repo as a submodule in other font repos wherefrom I can run the fontspector tests from the CLI – just so you can understand the context.

[simoncozens]

So yes, if you want to create your own checks then you will need a custom profile which implements checks, and that will have to be written in Rust. I guess a good first step is to discuss what you want to achieve because it might well be that the checks you want are generally useful and it would be worth including them in the fontspector core.

(For example, when you say "check of my metadata", other people - e.g. @Hoolean - have raised the idea of a check where you put some font parameters into the fontspector config file:

OS/2.sTypoLineGap: 0
name.DESIGNER: "Claus Eggers"

and it goes through the tables and checks them. Is that the sort of thing you are thinking of?)

Anyway, the direct answer to your question is:

• Create your own repo and copy in the contents of e.g. profile-microsoft. Customize the Cargo.toml and write your checks.
• In your own repo, you will need to set the dependency of fontspector-checkapi to

fontspector-checkapi = 1

so it gets fetched from crates.io. Additionally, any dependencies which use workspace = true need to be replaced with the corresponding entry from the Cargo.toml at the root of the fontspector repo.

• For development, build with cargo build which produces a file with the ugly name of target/debug/libfontspector_profile_claus.dylib or whatever. You can then use the path to this file as an argument to --profile.
• For personal deployment, build with cargo build --release and grab the file from target/release/.

From then on it's a matter of working out how you prefer to distribute the plugin binary to your other repositories. Popping the built binary into a repo and using it a submodule would probably work fine. But that's more of a general sysadmin/gitquestion than a fontspector one...

[clauseggers]

Thank you Simon. I believe it would be generally useful to have some facility in fontspector that enables us non-developers to construct simple tests in eg. the toml file or some other config file. Checks of the type “does this field contain this, if not throw an error”. Would certainly be helpful for the meta-data fields since they would be specific to each user/entity, possibly for other things – I haven’t gotten that far yet.

I’ll try my luck on adapting the Microsoft profile (or the Fontwerk profile since it had just such a metadata check I’m after), thanks.

[clauseggers]

I’m trying to make a custom profile that checks foundry metadata using a custom profile. However I can’t install this custom profile in the .fontspector/profiles/ directory and get it to work. Is this use of Fontspector supported?

[simoncozens]

What .fontspector/profiles directory? I don't think that's a thing...

[clauseggers]

I was guessing that was a thing. Can it be a thing? Should it be a thing? Reason is I have made a script that compiles the profile (as a dylib) and installs it in a .fontspector/profiles/foundryName/ directory. It seemed like a reasonable way to do this when the profile needs to be distributed to other users.

[simoncozens]

I was guessing that was a thing

That is an unusual approach to dealing with software. :-)

Can it be a thing? Should it be a thing?

I quite like the idea in theory. I would prefer "profiles live in .fontspector/profiles/" to "profiles live somewhere under .fontspector/profiles/*", because with a split directory, it's not clear to the user whether they should supply the full path (foundryName/profilename.fontspectorplugin or just the leaf profilename.fontspectorplugin.)

[clauseggers]

In the absence of documentation you make guesses ;-)

I would prefer to be able to put things in arbitrary directories under a .fontspector/profiles/ directory, then have Fontspector load them all, and then reference them without paths in the TOML files – ie. specifying just the leaf. This would require some file-naming collision handling. Reason for the custom directory is that I also copy the foundry-specific TOML file into the same directory. Without these sub-directories things could become a mess for the freelancers who need to install profiles from multiple foundries/clients/contexts.

[simoncozens]

I also copy the foundry-specific TOML file into the same directory

Wait, as well as what? If you have a plugin, that should be providing the entire profile, including the list of checks. I'm not sure why you would need a Rust plugin and a TOML file.

[clauseggers]

Alright. I’m have been trying to create this from scratch a few times now, but I keep running into segmentation faults when running the checks on a font. I can successfully compile and list the custom checks I made, but when I run it against a font I get segmentation faults. Notably I also get segmentation faults when I run the microsoft checks against a font. (I had to do this to make the Microsoft plugin compile #164)

Any ideas?

[simoncozens]

Are you running a fontspector you compiled yourself or one you downloaded? Just as a test it might be worth ensuring that both the fontspector binary and the plugin are complied in the same way.

[clauseggers]

This happens in both cases.