App switching allows user to interact with home screen contents for a fraction of a second

Number:rdar://FB9153889 Date Originated:10 June 2021
Status:Open Resolved:Open
Product:iOS Product Version:15.0 Developer Beta 1
Classification:Incorrect/Unexpected Behavior Reproducible:Always
Swiping using the home bar or switching to an unfocused app in the app switcher opens a ~1 second window in where any contents on the Home Screen below the app become interactive, and any clicks intended for the app get sent to the Home Screen and its contents. Attached is a screen recording demonstrating this with two Reminders widgets and multiple third party and Apple apps. First I show the widgets opening Reminders, then I demonstrate it in Messages, clicking as soon as the app comes into focus, and then demonstrate giving it a second in Settings, and then demonstrate it in TikTok.

Reproduction steps:
1) Open the app switcher and select an unfocused app (or swipe using the home bar)
2) Press an area on the screen where something is on your active Home Screen page within a second of the app being refocused
3) The content or app selected on the Home Screen opens

Expected behavior: 
App to be usable when put into focus

Actual behavior:
A second delay in between focusing and input, with all input in this timeframe going to the Home Screen


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