White line appears at top of screen in full screen mode

Number:rdar://FB8884688 Date Originated:11/5/2020
Status:Open Resolved:
Product:macOS Product Version:11.0, 11.1
Classification: Reproducible:Always
When my app is in full screen on Big Sur and the theme is light mode, a white line appears occasionally at the top of the screen.

I have a titlebar accessory view controller. This has been flaky during Big Sur, so my guess is that it’s involved.

To reproduce:
1. Install iTerm2 3.4.0beta13 from https://iterm2.com/downloads, or clone https://github.com/gnachman/iTerm2 and checkout commit 08faffe83b2209ad5b8f5196b7b116a485317d65 then build & run in Xcode.
2. Enter full screen mode
3. Type for a while. A white line periodically appears at the top of the screen.

You can see a screen recording here:

I am able to reproduce this easily on my own machine. I captured the view hierarchy (attached) and it does not appear there.

I have tried removing the title bar accessory view controller, but that does not solve the problem.

[sample project at https://iterm2.com/misc/whitebar.zip]


Still happening for macOS Monterey

iterm2 Build 3.4.4, Big Sur 11.2.3 (20D91) The problem still happens, and very annoying. I can't imagine Apple allows this bug to exist for such a long time. It doesn't help your users to have confidence in Apple product's quality.

This bug still exists, Hope this is being fixed. In the meanwhile, is there anything that App owners can do as a workaround fix for this?

By manideep.bvs at March 8, 2021, 3:40 a.m. (reply...)

As of today this bug still exists, quite annoying to be honest.

This affects me, too. Quite annoying.

By adamgeorgiou at Feb. 23, 2021, 6:19 p.m. (reply...)

iTerm Build 3.4.3 and macOS Big Sur 11.2 still happens.

By gabriel.sobrinho at Feb. 8, 2021, 3:21 p.m. (reply...)

Up to now, the bug stills exist

Report Build 3.4.20210125-nightly Mac Big Sur 11.1 This bug still exists. The only work around works for me is using dark mode. Well, I used to use light mode even at night, hope this to be fixed soon.

By hailiang.hl.wang at Jan. 28, 2021, 4:12 a.m. (reply...)

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