Draft: Content rating

[xi]

See #114

I worked on this during GUADEC, and I am not sure if I will be able to continue working on this any further. Unfortunately I did not get it to a usable state, but I will try to note down all interesting details so someone else can pick this up and finish the remaining bits and pieces.

gnome-software worked on this a while ago and upstreamed its logic into libappstream (see ximion/appstream@18c8b18). There are some details to this that we should consider:

• In libappstream, there is a difference between an empty and a missing content rating: empty means none, missing means unknown.
• They mapped each content rating item to a minimum age, then used the maximum of those. Then they used a locale-dependent rating system (e.g. ESRB for the US or FSK for Germany) to convert that minimum age to a string.
• In our case, the rating system will probably depend on the Accept-Language header, which is probably fine, but not a perfect match.
• Note that the mapping of content rating to a minimum age is not locale-dependent. So different cultural ideas about things like nudity are not accounted for.
• Most controversial is probably the mapping of sexual orientation. See https://gitlab.gnome.org/GNOME/gnome-software/-/blob/5f65a4a09d0892bb3b6e86ce2d02de880b8e52f5/src/gs-age-rating-context-dialog.c#L343.
• libappstream also provides localized descriptions of all content ratings. I was not sure how to integrate this with flathub's approach to i18n. We could either try to hook into that. Or we could duplicate the code.
• It would be nice to be able to color-code the minimum age. Unfortunately, the locale-dependent rating systems have different numbers of levels. I do not have a good idea about that yet.
• For the UI, I planned to have something that is similar to what we do for content safety. My idea was to map every content rating attribute to an icon and every level to a color.
• It turns out that most icon libraries do not have representations for stuff like violence-bloodshed readily available. It is probably a good idea to look into what gnome-software does.
• I did not yet have time to add https://schema.org/contentRating annotations

[xi]

I am not sure where this gets its locale from.

[razzeee]

Pylance complains here, I guess details = {} should work fine here

[razzeee]

Did you work this into the update routine at some point already?

[xi]

No, because I wasn't sure how to. See my comment above:

libappstream also provides localized descriptions of all content ratings. I was not sure how to integrate this with flathub's approach to i18n. We could either try to hook into that. Or we could duplicate the code.

[razzeee]

Looks promising, work should focus on the backend part for now

[razzeee]

kind seems to be wrong and should be type

[razzeee]

Pushed something that has started to work, more problems are:

• description doesn't get translated, do we need to do that on our end?
• we set a locale which is for e.g. de, but that's not mapping clearly to a rating system so we could assume de_DE, but it might be wrong