White rectangle at the bottom when tool bar's hiding

[bogdan-the-great]

Description

When I have hiding tool bar option turned on and try to scroll down to hide my tool bar, then for a split second I see a white rectangle at the bottom of my display (which is about the size of the hiding tool bar). I see this behaviour on every site I visit.

Environments

• Device 1: Huawei P10 Lite with LineageOS 15.1 (Android 8.1), WebView 86
• Device 2: Poco X3 NFC with AOSP Android 10, WebView 74
• Version: Both 1.9.24 from F-Droid
• Configuration: This bug shows up with the default configuration and it enabled

To reproduce

Steps to reproduce the behaviour:

1. Turn on: Look and Feel > Portrait > Hide tool bar when scrolling down
2. Go to e.g. gsmarena.com
3. Scroll down
4. For a split second you'll see a white rectangle at the bottom with the length of the hiding tool bar.

Expected behaviour

No rectangle popping at the bottom.

Screenshots

Screen record showing this behaviour

Notice how the rectangle is popping out. When trying it on SmartCookieWeb (which has smooth tool bar hiding) it didn't pop out.