What I am trying to do
I am building a browser-based exam proctoring platform that runs in Safari and Chrome on iPad. I need to detect when a candidate opens another app or browser tab in Slide Over (the floating panel) while the exam is running in the background. This is a pure web app - no native wrapper, no MDM.
What I've already tried
I tried listening to window blur and focus events neither fires when Slide Over is triggered on Chrome. I tried document.visibilitychange - same result, it never fires during Slide Over. I tried the resize event but it is completely inconsistent on iPadOS Chrome.
For Split View I am computing the ratio of window.innerWidth to window.screen.width and flagging below 0.80 as a likely split. That works. But Slide Over doesn't change the viewport at all - the exam tab stays full width in the background. So my ratio check is completely blind to it.
My question
Is there any JavaScript API, browser event, visualViewport property, or any other web-accessible signal that fires or changes when iPadOS enters Slide Over mode — specifically from a page running inside Safari or Chrome (WKWebView)? Even an indirect signal would help.
If there's truly no way to detect this from a web page today, is there a recommended pattern or workaround that others have used? I've seen the interaction heartbeat approach (flagging when no pointerdown arrives for N seconds) but that's too noisy for an exam context where a candidate may be reading a long question.