[Xcb] [RFC v0 proto] Add XInput2 protocol description

[Peter Hutterer]

On Mon, Dec 03, 2012 at 04:21:35PM -0500, Peter Harris wrote:
> On 2012-12-03 16:05, Daniel Martin wrote:
> > (In the following I'll write "XI2" when I mean the XInput extension
> > starting with version 2.0 and "XI" for the version up to 1.5.)
> > 
> > On Mon, Dec 03, 2012 at 09:56:26AM -0500, Peter Harris wrote:
> >> On 2012-12-02 16:05, Daniel Martin wrote:
> >>> Add the XInput2 protocol description for reviewing and feedback.
> >>
> >> I haven't had time to review the meat of this, but this stuck out on an
> >> initial glance:
> >>
> >>> +	xinput2.xml \
> >>
> >>> +<xcb header="xinput2" extension-name="Input2"
> >>> +     extension-xname="XInputExtension" major-version="2" minor-version="2">
> >>
> >> That's the same extension-xname as xinput.xml. I suspect the new
> >> definitions should be in xinput.xml, not in their own file.
> > 
> > I've choosen to make it in a seperate file, cause the extension name is
> > nearly the only thing both versions have in common and XI2 superseeds
> > the functionallity provided by XI.
> 
> Except for the QueryVersion request, which is only present in the XI1
> description. I suppose it could be duplicated in xinput2.xml, but see below.

I'm not sure I understand this comment. QueryVersion is an XI2-only request,
the equivalent in XI1 doesn't allow negotiating the client's version. 
There is also XI1's GetExtensionVersion which is XI1-only and should remain
in xinput.xml.

> > Supporting both versions is not necessary as the XI specification
> > states:
> >     "... New clients are discouraged from using this protocol
> >          specification. Instead, the use of XI 2.x is recommended. ..."
> > 
> > Mixing both versions in one file would cause to much confusions on the
> > (library) user side, as he wouldn't know which request is for which
> > version without having a look at the specification.
> > 
> > Due to that, the fact that the protocol description for XI is not
> > complete and XI is disabled by default in libXCB, I would rather mark it
> > as deprecated when this XI2 protocol description becomes usable. But, I
> > wouldn't like to merge them.
> 
> Be that as it may for libxcb, the Wireshark dissector generator is not
> expecting to find the same extension spread out over multiple files.
> 
> If we deprecate xinput.xml, we can move QueryVersion into xinput2.xml.
> But that leaves Wireshark without support for older (XI1) clients.
> 
> I'd generally prefer to keep the special cases to a minimum, but it's
> not all that much work to add extension merging (especially if you don't
> duplicate any requests) to the Wireshark generator. Before I do that,
> I'd like to hear if anybody else has an opinion on this topic.

I agree, XI2 isn't that special that it needs to be kept in a separate file.
makes for easier reviewing an testing, but this can be merged without ill
effects.

Cheers,
   Peter