There are a number of RL modules that use the wgMFMode client-side global configuration variable as a proxy for "is the user viewing the mobile version of the site", e.g.
var isMobile = mw.config.get( 'wgMFMode' ) !== null;
Yes, provided that it was considered stable (i.e. it would have to go through some deprecation process to change its name/value(s) or remove it).
Is this an acceptable use of wgMFMode?
In answer to this, I think no. wgMFMode was meant to tell the client whether the user was in beta mode or normal mobile mode. It got repurposed to mean mobile.
Yes, provided that it was considered stable (i.e. it would have to go through some deprecation process to change its name/value(s) or remove it).
I think to make it stable ideally we'd use a mw.util function allowing for us to change the class name in future.
Perhaps this work could be a precursor to feature management. "Mobile mode" is actually a feature, that's enabled in a certain situation (You are on a mobile device).
Perhaps we could use this as task to add some lightweight foundations for feature management in core (T242835)?
mw.util.isFeatureEnabled('mobile')Used by WikimediaEvents
Internally checks for classes on the body, that are added by the feature management system. e.g. mobile and visualeditor features may have the associated classes mw-feature-enabled-mobile and mw-feature-enabled-visualeditor
Utilized by MobileFrontend to check the requirement is met and to add it to the page.
I believe https://gerrit.wikimedia.org/r/c/mediawiki/extensions/MobileFrontend/+/782758 would solve this?
Change 782758 had a related patch set uploaded (by DLynch; author: DLynch):
[mediawiki/extensions/MobileFrontend@master] Add a body class indicating mobilefrontend is active
Change 782758 merged by jenkins-bot:
[mediawiki/extensions/MobileFrontend@master] Add a body class indicating mobilefrontend is active
To spell out the solution: that patch added mw-mf as a class on the body element, which will only be present if the site is in MobileFrontend mode (regardless of skins, etc). Anything that wants a binary "is MF active" can check for that, and TemplateStyles can hang themselves from it.
Change 809619 had a related patch set uploaded (by Phuedx; author: Phuedx):
[mediawiki/extensions/MobileFrontend@master] Hooks: Add wgMFIsActive client-side config variable
I've discussed this task further with @Jdlrobson and we both agree that:
I'm being bold and closing this task as Resolved.
Change 809619 abandoned by Phuedx:
[mediawiki/extensions/MobileFrontend@master] Hooks: Add wgMFIsActive client-side config variable
Reason:
Per https://phabricator.wikimedia.org/T299772#8109026