CAMetalLayer nextDrawable and macOS 10.14.4

Number:rdar://49804010 Date Originated:April 11 2019
Status:Open Resolved:No
Product:macOS + SDK Product Version:macOS 10.14.4 (18E226)
Classification:Graphics & Imaging Reproducible:Unable
We were instructed by DTS to file a bug report. The TSI reference number is [REDACTED].

Our remote management app, Royal TSX ( uses a CAMetalLayer by default for rendering RDP connections.
Since the 10.14.4 update rolled out officially, we've been getting a lot of crash reports from users which point to an issue with our Metal renderer or Apple's implementation of Metal.

We appended multiple crash logs to the bug report.

We looked through the code and couldn't identify any issues. Also, there have been no such reports before 10.14.4 rolled out. Unfortunately we haven't yet been able to reproduce the crashes here on any of our machines. What we gathered from searching the net for this is that it might be related to automatic graphics switching which we unfortunately can't test as we don't have access to a machine with multiple graphics cards that's also Metal capable.

Additionally, since we follow the development of Microsoft's Remote Desktop app closely, we recently noticed that an update was released which mentions that they've been working with Apple on resolving an instability issue related to graphics in 10.14.4. It very much sounds like they ran into the very same issue as us.

If necessary, we can provide the source code of our Metal renderer.

Steps to Reproduce:
Unknown at the moment but from user's crash reports it looks like it's related to automatic graphic switching. Users reported that the crash happened when returning from the screen saver, after switching to the login screen and logging back in, after returning their Mac from sleep and after switching between apps.

Expected Results:
Don't crash.

Actual Results:

macOS 10.14.4 (18E226)

Haven't been able to reproduce this on an iMac Pro and a 2016 MacBook Pro 13".


Apple Developer Relations

Please verify this issue with the macOS Mojave 10.14.5 beta 2 and update your bug report at with your results.

macOS 10.14.5 beta 2 (18F108f) Posted Date: April 8th, 2019

If the issue persists, please attach a new sysdiagnose captured in the latest build and attach it to the bug report. Thank you.

macOS sysdiagnose Instructions:

For a complete list of logging instructions visit:

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