Intent to Prototype: Automatic Fullscreen Content Setting
Mike Wasserman
Contact emails
Explainer
https://github.com/explainers-by-googlers/html-fullscreen-without-a-gesture
Specification
https://fullscreen.spec.whatwg.org/#dom-element-requestfullscreen
Design docs
Internal; will expand Explainer during prototyping.
https://docs.google.com/document/d/1yO5Ixgp6VNfYpGrqxezUmLaM-g_ZPGb16bxQ6_q9ln4
Summary
A new "Automatic Fullscreen" content setting permits Element.requestFullscreen() without a user gesture [1].
The setting is blocked by default. Users can allow Isolated Web Apps [2], and enterprise admins can allow additional origins.
Combined with Window Management permission [3] and unblocked popups [4], this unlocks valuable fullscreen capabilities:
- Open a fullscreen popup on another display, from one gesture
- Show fullscreen content on multiple displays from one gesture
- Show fullscreen content on a new display, when it's connected
- Swap fullscreen windows between displays with one gesture
- Show fullscreen content after user gesture expiry or consumption
[1] Also window.open()'s experimental 'fullscreen' feature; see https://chromestatus.com/feature/6002307972464640
[2] User control is initially scoped to security-sensitive apps; see https://chromestatus.com/feature/5146307550248960
[3] For multi-screen window placement features; see https://chromestatus.com/feature/5252960583942144
[4] To waive window.open()'s own user gesture requirements; see chrome://settings/content/popups
Blink component
Motivation
Some web apps (e.g. finance, gaming, point-of-sale, signage, and presentation) require multi-screen fullscreen from one gesture.
Virtual Desktop Infrastructure (VDI) clients also require fullscreen without a gesture to:
- Automatically extend a fullscreen desktop session onto a newly connected display
- Request fullscreen after transient activation expiry, e.g. slow remote host response
- Apply remote app fullscreen state locally, e.g. on app launch or system events
- Restore fullscreen on local display changes, local user session unlocks, other local OS Window Manager interruptions
Initial public proposal
https://github.com/whatwg/fullscreen/issues/234
Search tags
Fullscreen, requestFullscreen, transient activation, user gesture, content setting
TAG review
N/A; this is not proposing a new or changed web API, but a browser-specific permission configuration.
Risks
Interoperability and Compatibility
Element.requestFullscreen() may now succeed instead of rejecting without transient activation. The design doc considers some nuanced windowing corner cases. This feature is initially only available to security-sensitive apps and enterprise allow-listed origins.
Gecko & WebKit: N/A; this is not proposing a new or changed web API, but a browser-specific permission configuration.
Web developers: Positive.
Requested by 1st and 3rd party partners, particularly around VDI:
https://github.com/w3c/window-management/issues/7 https://github.com/w3c/window-management/issues/98 https://github.com/w3c/window-management/issues/92
Ergonomics
The explainer discusses potential feature detection methods.
Activation
Users or admins must grant the new Automatic Fullscreen content setting, plus the Popups & Redirects content setting and the Window Management permission, and to take full advantage of fullscreen windowing features.
Security
This capability exacerbates preexisting fullscreen usable security concerns, so sites cannot show a permission prompt, and user controls are initially scoped to IWA contexts.
WebView application risks
None
Debuggability
Sites can debug via Element.requestFullscreen()'s promise, which may reject with a TypeError containing a message, supplemented by devtools console messages. Transient activation state is exposed via navigator.userActivation.isActive. Script can check the window.location.href's scheme for `isolated-app:` to assess initial availability of user control for the current context.
Is this feature fully tested by web-platform-tests?
No. WPT coverage is not yet available, and necessitates test driver controls for this new content setting.
DevTrial instructions
https://github.com/explainers-by-googlers/html-fullscreen-without-a-gesture/blob/main/HOWTO.md
Flag name on chrome://flags
chrome://flags/#automatic-fullscreen-content-setting
Finch feature name
AutomaticFullscreenContentSetting
Requires code in //chrome?
True; for content settings and enterprise policy management.
Tracking bug
https://bugs.chromium.org/p/chromium/issues/detail?id=1501130
Launch bug
https://launch.corp.google.com/launch/4296344
Measurement
Blink.UseCounter.Features: kFullscreenAllowedByContentSetting
Adoption expectation
Feature is used by specific partner(s) to provide functionality within 12 months of launch in Chrome
Sample links
https://github.com/michaelwasserman/iwa-windowing-example
Estimated milestones
Shipping on desktop 126
DevTrial on desktop 123