Dark mode support for web apps

[loubrett]

Braw mornin' TAG!

I'm requesting a TAG review of dark mode support for web apps.

This feature adds a user_preferences manifest member which allows apps to specify a different theme color and background color for dark mode and other user preferences in the future.

"user_preferences": {
    "color_scheme_dark": {
        "theme_color": "#000"
        "background_color": "#000"
    }
  }

• Explainer: https://github.com/WICG/manifest-incubations/blob/gh-pages/user-preferences-explainer.md
• Tests: None in WPT yet
• Security and Privacy self-review: Minimal security/privacy effects. This will allow sites to know which user preferences are set but this information is already exposed through CSS.
• GitHub repo: https://github.com/WICG/manifest-incubations
• Primary contacts (and their relationship to the specification):
  • Louise Brett (loubrett), Google
  • Glen Robertson (phoglenix), Google
  • Matt Giuca (mgiuca), Google
• Organization(s)/project(s) driving the specification: Google
• External status/issue trackers for this specification (publicly visible, e.g. Chrome Status):
  • https://chromestatus.com/feature/5714780426862592
  • https://crbug.com/1271804

Further details:

• I have reviewed the TAG's Web Platform Design Principles
• Relevant time constraints or deadlines: Targeting origin trial in M99
• The group where the work on this specification is currently being done:https://github.com/WICG/manifest-incubations
• The group where standardization of this work is intended to be done: https://github.com/WICG/manifest-incubations
• Major unresolved issues with or opposition to this specification: None
• This work is being funded by: Google

We'd prefer the TAG provide feedback as:

💬 leave review feedback as a comment in this issue and @-notify loubrett

[cynthia]

High-level first pass question: While the user needs make a lot of sense, wouldn't putting it into only manifests be problematic for non-installable webapps?

[loubrett]

It is already possible to define this in CSS - adding it to the manifest allows these colors to be used while the app is opening, before the page has loaded.