A bunch of people have reported problems with Edit Mode on MacOS (and some on Linux). Basically the overlay display and interactive selection tools aren’t working (detailed in https://developer.blender.org/T79811 which a few reports have been merged into). Basically master has been unusable for a while. Currently unassigned. I’ve been looking at code to see if I can spot what’s wrong but I don’t know my way around the code well enough (for the time I have anyway). Anyone familiar with this part of the code want to walk me through some relevant bits?
This is pretty technical stuff, if you’re not familiar with OpenGL and its management of vertex buffers and array objects it’s going to be difficult to do much.
I’m actually quite familiar with OpenGL+extensions and Metal. But every application establishes its own conventions for how things are leveraged to achieve assorted effects, how OpenGL structures map to other internal representations (Blender seems to have a few distinct internal representations), etc… Basically I have to learn my way around the Blender code base. I haven’t found documentation for the new display code/algos introduced with 2.80+. So I wonder what the best way to get up to speed is.
I don’t think there is documentation for this part of the code besides the comments, and it’s changing often still as this is being refactored.
You could ask Clément for some hints in the bug report.