Wait @davidedmundson to accept it.

Do I need to change anything or is this acceptable?

gitlab-migration branch was merged.

Could that also mitigate task manager showing windows of the wrong screen in certain scenarios?

The biggest problem with sharing the dmabuf buffers it that its memory management becomes quite complex (and I'm unsure it's really doable).
PipeWire has mechanisms to create the buffers it's going to need, juggling this with passing the buffer from the app/output and making sure it stays relevant feels messy and error-prone.
Copying from dmabuf->dmabuf shouldn't be very expensive though, as it shouldn't go through the buses (AFAIK, that is).

Shouldn’t this be added to T10891?

@meven Have you already got in contact with the other users/maintainers of he thumnbail cache spec about the idea to extend it with support for high dpi? If not, please consider to do so, so things will also work cross-toolkit/platforms in the future there, by being based on an agreed & formalized specification. Not being involved here or having full understanding of the topic, but I would guess your approach with the separate x2 should run into "make sense" responses, so the additional effort might be low for the gain of being based on an official spec.

In D29487#673803, @davidre wrote:

Ping. Did you have time to look into

I noticed a flaw however in the current code if the first instance of spectacle is started with --new-instance a second one will always be started when the shortcut is pressed regardless of the setting.