I just got this working. Thank you! Besides waitUntilCompleted as you recommended, I also switched from MTKView to a lower level technique using CAMetalLayer (following an Apple sample project named "CustomMetalView"). That may not be necessary but in my situation it helped. Now when I'm in LLDB and I step across a change in the data model, I can call a certain Swift function (p debugRender()) and I see the change on my device screen. Sweet!

You didn't get the 3 bar icons on the right side, after tapping "Edit". That's odd. I see it on my device. You drag that to move them. As for the circles, I left that to you. Now it just turns the text green, but you can conditionally draw a colored circle using SwiftUI shapes, like Circle.

I just tried a \< (backslash escape), and that still triggers the monospace for me.

In the package, do you have a .h file containing types for the metal shaders? Or did you just paste the types into the .metal shader files? I tried the former, but I don't think the .h file was being picked up my the .metal or the .swift files. Maybe I need to say something in the Package.swift to tell it about the .h file.

Found an answer: add .compositingGroup() modifier to second picker to fix the touch target issue.

Yup, that fixes it. Thanks.

I just pasted your exact code into a new project, and it causes the problem for me. The border between the touch areas is way right of center, not in the center as it should be. I'll add an 'answer' with a screenshot, in a moment. I thought I could edit my question to add a screenshot, but apparently I can't.

Are you getting wheels or menus? I had to add .pickerStyle(.wheel) because the default seems to have changed. I forgot to add that to my question. I will edit the question now.

This has stopped working in iOS 15. I'm looking for another workaround. The widths still split 50/50 as desired, but the touch target area seems to overlap, so dragging on the first picker causes the second wheel to scroll, unless you touch way towards the edge of the screen.