[Qemu-devel] console muti-head some more design input

[Dave Airlie]

So I've started banging my head against using QemuConsole as the
container for a single output, and have been left with the usual 10
ways to design things, but since I don't want to spend ages
implementing one way just to be told its unacceptable it would be good
to get some more up front design input.

Current code is in
http://cgit.freedesktop.org/~airlied/qemu/log/?h=virtio-gpu-multiconsole

So I felt I had a choice here for sharing a single output surface
amongst outputs:

a) have multiple QemuConsole reference multiple DisplaySurface wihch
reference a single pixman image,
b) have multiple QemuConsole reference a single DisplaySurface which
reference a single pixman image.

In either case we need to store, width/height of the console and x/y
offset into the output surface somewhere, as the output dimensions
will not correspond to surface dimensions or the surface dimensions
won't correspond to the pixman image dimensions

So I picked (b) in my current codebase, once I untangled a few
lifetimes issues (replace_surface - frees the displaysurface == bad,
this is bad in general), I've stored the x/y/w/h in the QemuConsole
(reused the text console values for now),

Another issue I had is I feel the console layer could do with some
sort of subclassing of objects or the ability to store ui layer info
in the console objects, e.g. I've added a ui_priv to the
DisplaySurface instead of having sdl2.c end up with SDL_Texture array
and having to dig around to find it.

At the moment this is rendering a two-head console for me, with
cursors, with virtio-vga kernel and Xorg modesetting driver persuaded
to work, but I'd really like more feedback on the direction this is
going, as I get the feeling Gerd you have some specific ideas on how
this should all work.

Dave.