winex11: Always use the Virtual Core Pointer for raw events

[Henri Verbeet]

On 12 November 2016 at 17:14, Carlos Garnacho <carlosg at gnome.org> wrote:
> Second, in the unlikely case that Wine managed to detect a master
> pointer other than the VCP (this requires user intervention, creating
> a second pointer/keyboard pair and assigning HW devices to it) This
> second pointer would be unaffected by the core X calls performed by
> Wine (eg. grabs,cursor). This could eg. result in Wine grabbing/confining
> one pointer, while listening to raw events from another, which is
> otherwise unaffected by the grab.
>
I'm not sure that's necessarily wrong, but using XIGrabDevice(),
XIWarpPointer(), etc. would probably be enough to fix that.

> The Virtual Core Pointer is a given, it always has ID=2, it's created
> by default, it can't be removed, it's the one getting HW devices attached
> to by default, and it will be the device implicitly used by the other
> X core calls. It's the device Wine wants to listen to despite its initial
> state.
>
That probably works in practice, but I can't think of anything in the
protocol spec that guarantees the VCP has id 2. Did I miss something
there? How about XIGetClientPointer(), would that do the right thing?

> The main purpose of this patch is fixing master device detection over
> Xwayland, which is affected by the relative axes check. Xwayland will
> most usually emit pointer events as coming from a device with absolute
> axes, only switching to emitting relative motion when a very specific
> set of conditions are met (thought out for gaming basically). But most
> usually these conditions don't apply yet when XI2 is enabled, so the
> VCP is skipped and it ends up with xi2_core_pointer=0, thus ignoring
> the relative motion that is later sent.
>
> But again, this is not Xwayland specific, it could happen as well with
> the right conditions on traditional X servers.
>
Wouldn't the correct way to handle this kind of thing be to respond to
XI_DeviceChanged and XI_HierarchyChanged events?