export-dmabuf is racy

[emersion]

To fix the race:

• Add a way for the client to signal to the compositor that they're done with the buffer
• Maybe add a way for the compositor to tell the client that they're too slow

(How does that play with explicit sync?)

[emersion]

Add a way for the client to signal to the compositor that they're done with the buffer

Actually we already have the destroy request for this.

Maybe add a way for the compositor to tell the client that they're too slow

After discussing on IRC, probably not. Many clients (e.g. those using hw encoding) won't be able to cope with a frame becoming invalid.

Instead, check whether the client holds too many DMA-BUFs when sending DMA-BUFs.

[emersion]

wlr-protocols has migrated to gitlab.freedesktop.org. This issue has been moved to:

https://gitlab.freedesktop.org/wlroots/wlr-protocols/-/issues/74