[PATCH wayland 0/3] "enum" and "bitfield" attributes for protocol XML files

[Pekka Paalanen]

On Fri, 26 Jun 2015 16:02:44 +0200
Auke Booij <auke at tulcod.com> wrote:

> As per last April/May's "enum" attribute discussion, these patches
> introduce two new attributes to the protocol XML files.
> The "enum" attribute is given to <arg>uments of type (u)int, and
> indicates which <enum> should be used for that argument.
> The "bitfield" attribute can be given to <enum>s, and, if set to "true",
> indicates that the enum is to be thought of as a bitmask-style value.
> 
> Although arguments can only refer to enums in specific cases (see the
> scanner.c changes), this new protocol data should not break the C bindings.
> It is thinkable that other bindings *do* use the data in a way that breaks
> the protocol; however such usage will be considered nonstandard.
> 
> Auke Booij (3):
>   protocol: introduce the enum argument type
>   scanner: enforce correct argument type for enums
>   doc: document new enum attributes and use such data in generated docs

Hi Auke,

so we've had a huge amount of discussion recently and I'm sure you have
lots of ideas already. I'm not going to summarize that discussion, but
propose more technical improvements here.

I think it would make sense to order the patch series in reverse:
1. XML language spec (and the DTD if you want to update that)
2. wayland.xml
3. scanner
4. doc generator

That way we start with the XML language specification. Then add the new
things to wayland.xml. At this point we see that old wayland-scanner
still works. Then update wayland-scanner, and finally the doc
generator. So the doc patch would be split in two.

Reviewers will then verify the (absence of) changes in the generated C
bindings.

I think I discussed with Victor in IRC about testing old
wayland-scanners. It shouldn't be too difficult to write a script that
checks out each of the ten 1.x.0 Wayland releases, builds
wayland-scanner from it, and runs it on the tip wayland.xml. Maybe
someone could contribute such a script. I think it might be handy in
the future too.

In Patch 1 for the XML language spec, I think you could start a new
section "XML Language" or such, and specify all these new concepts and
attributes there. You can start it with a blanket paragraph that says
the authoritative basic definition of the language is what
wayland-scanner implements, and this section just adds to that. This
way we will have a place to start gathering the language doc.

I think the section "code generation" is more like how to do language
bindings, so if someone wants to get started on that, that would be the
place. What is right now in "code generation" could be split between
"basic principles" (we have this XML files thing) and C bindings.

If you want to avoid revising all the patches, you could start by
posting an RFC of only the first patch. That's what everyone has been
fighting over anyway. When people are generally happy with that, you
could do the full series.

How's that?


Thanks,
pq
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