Get wlr-gamma-control into wayland-protocols
A new protocol to allow privileged clients to set the gamma tables for outputs. And as a result, allowing changing brightness, contrast, saturation, and gamma levels of the whole desktop (clients and shell). Similar to or like wlr gamma control.
Forgive me if I don't use the correct Wayland and color management terminology or know more technical details about this proposal.
A clear use case is color temperature adjustment and using things like Redshift. As I understand it, the decision about color temperature was that it should be a compositor implementation because it's not wanted that clients arbitrarily change the desktop colors. Unfortunately, an issue with this approach is that the compositor implementation may not have all the features wanted or just have important bugs (Gnome).
Though I understand how allowing any client to modify the desktop colors is annoying, a better approach may be using portals for users to be able to only explicitly allow the clients they want to change the gamma tables. And as for changing the gamma, brightness, contrast, and saturation, it's something that usually can be configured on monitors/TVs or through software, like on Windows with the graphics drivers configuration GUIs.
In X11 also somewhat lacks this, except for gamma, though a convoluted workaround was modifying ICC profiles or using Gamma panel through Wine. And using libvibrant for the saturation.
In Wayland using gamma panel through Wine is not possible, and the only workaround is using ICC profiles, like Gnome gamma tool. The issue with this approach is that it's not accessible and easy to use at all, and with it, it's not possible to change the saturation.
For me, being able to change the colors like this is a dealbreaker over the daily use of Wayland, though the Gnome gamma tool is itself a solution but has its limitations.
As I said, I don't have the knowledge of the details on how this could be implemented. But probably at first (!14 (merged)) would be needed.