On Mon, 29 Mar 2021 15:36:27 +0000 Simon Ser contact@emersion.fr wrote:
On Monday, March 29th, 2021 at 5:32 PM, Paul Cercueil paul@crapouillou.net wrote:
Making the second plane an overlay would break the ABI, which is never something I'm happy to do; but I'd prefer to do it now than later.
Yeah, I wonder if some user-space depends on this behavior somehow?
I still have concerns about the user-space being "clever" enough to know it can disable the primary plane. Can e.g. wlroots handle that?
wlroots will always pick the first primary plane, and will never use overlays. The plan is to use libliftoff [1] to make use of overlay planes. libliftoff should already support the scenario you describe.
I think Weston supports that too.
Weston supports overlays, but I don't think it will try without "the" primary plane, IIRC. I'd need to verify.
I'm not quite sure what Weston would do with multiple primary planes. It probably picks one for a CRTC ahead of time, and then sticks to it, always using it.
But if Weston never worked with a driver to begin with, it also can't regress, so you're safe.
Thanks, pq
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