I mean zero of the Metal sample apps even set a colorspace. So what do we reference here? macOS and iOS are supposed to be the ultimate "color managed" platforms, although iOS couldn't afford the pixel ops on the first phones/iPads.
Am I tagging my pixels which are linear as srgb, do I need a transfer function to be gamma 1 or gamma 2.2? What is kCGColorSpaceSRGB vs. kCGColorSpaceLinearSRGB. These are both srgb colorimetry, but am I stating that my content has the srgb gamma curve in the former, and is linear in the latter? And how to get the cheapest pass through. I can set my display color space to sRGB (709) or P3, but how do I get the cheapest, fastest, and highest quality pixel output to screen. Before all the color management, on iOS I had to use BGRA8 instead of RGBA8 to avoid a swizzle blit. These are the kind of details that are sorely lacking even in the WWDC presentations.
There is also true tone, and the user adjusting the maximum brightness of the display. So those also need to be responded too. And what to do when NSApplicationDidChangeScreenParametersNotification calls and says screen.maximumExtendedDynamicRangeColorComponentValue changed.