> Requiring every game [..] to decide how to do it's HDR->SDR seems unnecessary complication due to poor abstractions.
Games already do this regardless and it's part of their post processing pipelines that also govern aspects of their environmental look.
What's missing is HDR->Display which is why HDR games have you go through a clunky calibration process to attempt to reverse out what the display is going to the PQ signal, when what the game actually wants is what MacOS/iOS and now Android just give them - the exact amount of HDR headroom which the display doesn't manipulate.
As for your other examples, being able to target the display native range doesn't mean you have to. Every decent os has a compositor API that lets you offload this to the system.
Yes, if local tone mapping is done by the operating system (windowing system or the monitor itself), then there is a chance that borders of windows are done appropriately within their spatial context.
Games already do this regardless and it's part of their post processing pipelines that also govern aspects of their environmental look.
What's missing is HDR->Display which is why HDR games have you go through a clunky calibration process to attempt to reverse out what the display is going to the PQ signal, when what the game actually wants is what MacOS/iOS and now Android just give them - the exact amount of HDR headroom which the display doesn't manipulate.
As for your other examples, being able to target the display native range doesn't mean you have to. Every decent os has a compositor API that lets you offload this to the system.