Pro Display XDR loses HDR color detection/support

[sbrichardson]

I noticed one hiccup with HDR support, I'm not sure exactly what is causing it.

Hardware Setup

• 14" M1 Max MacBook Pro (closed in clamshell mode)
• Dual Pro Display XDR displays (both in P3-1600 nits mode)
• macOS Monterey 12.0.1

BetterDummy Config

• Two 16x9 dummies at 3840 x 2160
• Each Pro Display XDR configured to mirror a dummy.
• In display preferences, all set to optimize for the dummy.
• Version 1.0.9 Build 544

Issue Details

While using Google Chrome/Chrome Canary/Safari, viewing an HDR video on YouTube, when BetterDummy is active/mirroring, the HDR color modes are not offered within YouTube. If you stop mirroring or close BetterDummy and refresh the browser, the HDR video options show up properly (in YouTube).

I'm not sure if HDR is not working altogether, or the monitor/color profile detection that the browsers are using just won't recognize BetterDummy. I tried changing the color profile of the dummies in System Preferences, but none would fix this issue. I tried reopening the browsers to force HDR detection.

Test Note

Another test, I mirrored one dummy/XDR display and left the other XDR display at native settings. Opening YouTube on the native display, HDR works fine. While the video was playing in HDR, without refreshing the tab, I dragged the browser window to the dummy mirrored XDR display and HDR clearly wasn't enabled.

I tried forcing various HDR color profiles within chrome://flags, without any luck. #force-color-profile

Context

My reason for using BetterDummy was to enable 4K HiDPI resolution on the Pro Display XDRs, since the native resolution is limited to 3K HiDPI on M1 Apple Silicon, which results in the UI being slightly too big. It works perfectly except for this HDR issue.

-- Thanks for your excellent work on this app

[waydabber]

Hey @sbrichardson,

I am unable to experiment with it directly as I don't have any HDR capable hardware at all, but my suspicion is that virtual screens can't handle HDR on macOS at the moment. According to reports, Sidecar is unable to reproduce HDR content on an iPad Pro 12 for example (this is relevant because Sidecar uses the same virtual display technology as BetterDummy). I can specify colorsync information for the virtual display (whitepoint and gamut - color space tistimulus - info), but this doesn't relate the question of supported dynamic range at all. HDR is a bit messy in macOS, hopefully future iterations of CGVirtualDisplay will handle this better somehow (I think this will be happening when HDR will be mainstream and Apple will solve HDR for Sidecar or AirPlay mirroring).

Anybody else who has HDR display and would like to experiment with this or give more input, please add your voice. I'll tag this issue as Help wanted.

Thanks!

[waydabber]

Until Apple starts supporting HDR for CGVirtualDisplay, this will not be fixed I am afraid. This is listed in Known Issues in the Readme. No reason to keep this issue open here. I'll convert this into to a discussion.