Hacker News Reader

Comment by audidude | Hacker News Reader

This would require protocol changes for X11 at best, and nobody is adding new protocols. Especially when nobody does Drawable of Drawables anymore and all use client-side drawing with Xshm.

You need to dynamically change stacking of subsurfaces on a per-frame basis when doing the CRTC.

View on HN

I really don't see why it would need a new protocol. You can change stacking of "subsurfaces" in the traditional X11 fashion and you can most definitely do "drawables of drawables". At the very least I'd bet most clients still create a separate window for video content.

I agree though it would require a lot of changes to the server and no one is in the mood (like, dynamically decide whether I composite this window or push it to a Xv port or hardware plane? practically inconceivable in the current graphics stack, albeit it is not a technical X limitation per-se). This entire feature is also going to be pretty pointless in Wayland desktop space either way because no one is in the mood either -- your dmabufs are going to end up in the GPU anyway for the foreseeable future, just because of the complexity of liftoff, variability of GPUs, and the like.

> I really don't see why it would need a new protocol.

You'll need API to remap the Drawable to the scanout plane from a compositor on a per-frame basis (so when submitting the CRTC) and the compositor isn't in control of the CRTC. So...

This assumes it would be the role of the window manager or compositor rather than the server who decides that, which I didn't think that way. But I guess it'd make sense (policy vs mechanism). "per-frame basis" I don't see why and it just mirrors Wayland concepts. Still, as protocols go, it's quite a minor change, and one applications don't necessarily have to support.

The server doesn't have enough information to do it because it doesn't know anything about window management. At best it could use a heuristic to guess, but one of the reasons Wayland combines the server and the compositor is so that we don't need to pile heuristics into the X server and drivers any more.

Nothing in Xorg is a minor change because it has to be tested with every window manager and compositor before you can even think about merging.

Reply on news.ycombinator.com