And can you not see how that’s a problem? Software that was written without using XDG portals shouldn’t have to be concerned about their existence. If it is required that existing, finished software has to adapt to a new paradigm, it is not a replacement - it’s new. And it’s intrusive. If you replace the water system for a house, that’s one thing. If you replace the water system in the house AND the new system requires the owner to buy and install all new fixtures on all the faucets, that’s an entirely different thing altogether.
Wayland isn’t a piece of software. It is simply a set if standards apps use to talk to the desktop which then talks to the kernel and hardware.
Apps access resources via XDG portals. If there isn’t a portal for something it needs to be implemented at the desktop.
Back to your use case, I think you probably just need the appropriate desktop extension. Drawing on the desktop sounds like a desktop level thing.
And can you not see how that’s a problem? Software that was written without using XDG portals shouldn’t have to be concerned about their existence. If it is required that existing, finished software has to adapt to a new paradigm, it is not a replacement - it’s new. And it’s intrusive. If you replace the water system for a house, that’s one thing. If you replace the water system in the house AND the new system requires the owner to buy and install all new fixtures on all the faucets, that’s an entirely different thing altogether.