Enums, bitfields and wl_arrays

[Pekka Paalanen]

On Fri, 2 Oct 2015 12:53:13 +0100
Auke Booij <auke at tulcod.com> wrote:

> On 1 October 2015 at 20:00, Nils Chr. Brause <nilschrbrause at gmail.com> wrote:

> > I would prefer, if the enum attributes would also name the interface,
> > where the enum can be found, e.g.:
> >     <arg name="format" type="uint" enum="wl_shm.format"/>
> > If two enums in different interfaces happen to have the same name (if
> > that's possible?), this would lead to ambiguities otherwise. Also a
> > scanner wouldn't have to look up the interface name that way.
> 
> While in principle I think this is a great idea, this will need a few
> specifications, which is why I decided not to add those in just yet.
> Are cross-XML references allowed in this sense? In that case, the
> scanner cannot verify their correctness, since only the current XML
> file is available to it. Additionally, moving a certain interface from
> xdg_shell to the core wayland protocol would now mean potentially
> having to weaken the type safety of an interface, or having to copy
> the enum over.

Hi,

yeah, adding the interface name makes perfect sense. It could be
optional if wanted. No dot would mean the enum is in the same
interface, a dot would signify a specific interface. I don't think
there is any use for an anonymous global namespace like Bill mentioned.

As for link validity check, I could live with checking it only if the
mentioned or implied interface is defined in the same XML file. This
should cover most cases, and the rest would manifest as compile errors
on non-C language bindings.

It's really all we can do anyway. XML files are perfectly allowed to
reference interfaces defined elsewhere, even in XML files not available
at the time.

A generator could have an extended check mode, where you can feed it a
bunch of XML files for reference, while generating the code just for
one, but I don't think it would be a good idea to absolutely require
that on the XML language spec level, because it would again break old
build systems.

Btw. when xdg-shell or any other new extension gets promoted to Wayland
as stable, it will not be appended into wayland.xml. It will simply be
yet another XML file to be installed by libwayland. Furthermore,
libwayland will not install pre-generated C-bindings for it. All
projects using the extension need to run wayland-scanner or any other
generator during their build.


Thanks,
pq
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