explainers-by-googlers/locked-mode

Provides a way for a site to prompt the user to enter a locked-down fullscreen mode, and the user cannot 1) use other apps and OS features or 2) exit this mode without notifying the site. Enables users to take low-stakes tests or focus on specific contents in a classroom setting.

locked-mode's Issues

Do request() and exit() resolve with a value?

From the API description and example, it's not clear if the intention is for nagivator.lockedMode.request() and nagivator.lockedMode.exit() to resolve with some value other than undefined. The example code saves enterResult and exitResult but I suspect there's no useful value to return.

Permissions Policy integration

Fullscreen API specifies a Permissions Policy-controlled feature called fullscreen with default allow-list of self.[1] This proposal appears to lack an explicit separate feature for locked and unlocked fullscreen mode. Given the potential for abuse of a system-level full-screen lock, is there any interest in introducing a separate sub-feature specifically for the lock, e.g. called fullscreen-lock?

[1] Fullscreen API specification paragraph 6 "Permissions Policy Integration"

Feature detection of requestFullscreen() extensions would be possible

The explainer says:

Does not allow developers to detect the Locked Mode feature by checking the existence of a separate API

Although complex, feature detection is possible if we're considering new dictionary members. Example using navigationUI:

let supported = false;
document.createElement('div').requestFullscreen({
  get navigationUI() { supported = true; }
}).catch(() => {});
console.log(supported);

This will make its way through bindings and access navigationUI of the options object passed in, but the request will be rejected and do nothing because the element isn't attached.

Behavior in iframes?

Should the API only work for top-level browsing contexts, or what does nagivator.lockedMode.request() do inside an iframe?