BGFX_CONFIG_MAX_FRAME_LATENCY bad implementation on OSX

[alexgu754]

any project that uses bgfx including the sample projects have very bad frame lag that you can do absolutely nothing about (apart from turning off vsync), making it practically unusable for realtime applications with vsync enabled.
the problem is only the number of active command buffers is limited by BGFX_CONFIG_MAX_FRAME_LATENCY, but when a command buffer submits, that doesn't mean the frame has been presented or about to be presented. So you're submitting command buffers one after another in the while game loop and overflowing the CAMetalLayer*'s 4 drawable limit and then the application halts when next drawable is called for the drawable to free up, then you enqueue that drawable at the very back. you have to use 'addPresentedHandler' or 'drawable.presentedTime' to actually set a frames in flight limit, and its also a very good idea to use CVDisplayLink or NSView.displayLink to also reduce latency. If you do this you'd have perfect synchronisation with the os mouse, but right now its very unresponsive

513545998-6b7180d9-c3a7-4134-9dfa-691dee6d2987.webm

[alexgu754]

I can implement this at some point, but this has to be one of the top priorities, has a big impact on macos users and gamers and hasn't been addressed in all these years

[alexgu754]

Ok I tried changing renderer_mtl.mm and there were random frame drops for some reason and I honestly don't want to invest more time into this, maybe drawables were being discarded without doing the drawn callback, and I'm not using bgfx anymore so its no benefit to me
I made this repo for reference for what it should be that uses sdl3
https://github.com/alexgu754/LowLatencyOSX/tree/main