Mission Control bug causes Catalyst app windows to be much brighter

[f1vespeed]

See video:

Ran across this weird Mission Control bug that only seems to affect Catalyst apps. (Messages, Podcasts so far). The screen gets really bright just within the bounds of the app's window, it almost looks like the display has local backlight dimming that breaks for those apps.

I know the MBA doesn't have local dimming, but I'm wondering if anyone can explain this phenomenon. It only happens when the screen is at less than 100% brightness, and it causes the Catalyst app's window to look about twice as bright as everything else. As I vary screen brightness, the difference remains about the same proportionally (i.e. if the screen is at a very low brightness setting, the Catalyst app is brighter, but not insanely bright).

I'm guessing this betrays how screen brightness works on the Mac, which I've never really thought about. I guess the backlight is quite a lot brighter than the brightness of the white areas on the screen at less than full brightness, and MacOS is actually displaying some shade of grey instead of pure white?

 

[f1vespeed]

I will add that my iPhone's camera is adapting pretty quickly to the change in brightness, so it's hard to tell from the video just how much brighter the screen area of the Catalyst app gets upon invoking mission control (I'm using my trackpad to do it slowly in the above video)

 

[Ritsuka]

Those are Catalyst apps. Are you playing back an HDR movie? That could happen if the display is in the EDR mode: https://michelf.ca/blog/2020/brighter-than-white-edr-on-macs/

 

[f1vespeed]

Those are Catalyst apps. Are you playing back an HDR movie? That could happen if the display is in the EDR mode: https://michelf.ca/blog/2020/brighter-than-white-edr-on-macs/

Ah whoops, corrected Electron to Catalyst.

No, I'm not playing back video of any kind. Even if I were, seems odd that a single window would behave that way, and only under mission control.

This M1 MacBook never gets plugged into any external displays either.

 

[f1vespeed]

Those are Catalyst apps. Are you playing back an HDR movie? That could happen if the display is in the EDR mode: https://michelf.ca/blog/2020/brighter-than-white-edr-on-macs/

Thanks for the reading material on EDR!

It definitely seems like a bug. I could imagine part of the screen being brighter where an image or video is being rendered with the appearance of HDR under EDR, but not the entire Podcasts or Messages app UI.