Many people are, understandably, confused about brightness levels in content creation and consumption - both for SDR and for HDR content. Even people that do content creation as their job sometimes get it really wrong.
Again, the reference luminance mapping is all about how applications should use the Wayland protocol.
How to map SDR to HDR can indeed be made much more complicated, from simple gamma adjustments to some full blown ITM meant for images or videos, like what BT.2446 suggests, but as far as applications are concerned, those are edge cases that they don’t really need to be prepared for.
It’s not like they have a different choice - unless the compositor supports custom reference luminance levels (which KWin does, but not all others do), then they need some logic to calculate peak luminance levels. If the compositor steps outside of those common expectations for reference luminance mapping, then the result may not be ideal, but there is no way for the application to do better.
Again, the reference luminance mapping is all about how applications should use the Wayland protocol.
How to map SDR to HDR can indeed be made much more complicated, from simple gamma adjustments to some full blown ITM meant for images or videos, like what BT.2446 suggests, but as far as applications are concerned, those are edge cases that they don’t really need to be prepared for.
It’s not like they have a different choice - unless the compositor supports custom reference luminance levels (which KWin does, but not all others do), then they need some logic to calculate peak luminance levels. If the compositor steps outside of those common expectations for reference luminance mapping, then the result may not be ideal, but there is no way for the application to do better.