[PATCH wayland 4/7] Add support for custom dispatchers

[Pekka Paalanen]

On Mon, 18 Feb 2013 10:03:25 -0600
Jason Ekstrand <jason at jlekstrand.net> wrote:

> 
> Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
> ---
>  src/connection.c        | 15 +++++++++----
>  src/wayland-client.c    | 13 +++++++++--
>  src/wayland-private.h   |  3 ++-
>  src/wayland-server.c    |  9 +++++++-
>  src/wayland-util.h      | 27 ++++++++++++++++++++--
>  tests/dispatcher-test.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 117 insertions(+), 10 deletions(-)
> 
...
> diff --git a/src/wayland-util.h b/src/wayland-util.h
> index df7b384..b77a122 100644
> --- a/src/wayland-util.h
> +++ b/src/wayland-util.h
> @@ -46,18 +46,41 @@ struct wl_message {
>  	const struct wl_interface **types;
>  };
>  
> +union wl_argument;
> +struct wl_object;
> +
> +typedef void (*wl_interface_dispatcher_func_t)(struct wl_object *, uint32_t,
> +					       const struct wl_message *,
> +					       void *, union wl_argument *);
> +/**
> + * wl_interface - object method interface
> + *
> + * This structure has been extended since libwayland version 1.  The version
> + * field now represents both an interface version and a structure version.
> + * The upper 16 bits represent the version of the structure with the original
> + * version being version 0.  The lower 16 bits represent the interface version
> + * as specified in the interface XML file.
> + *
> + * This way, as long as the version number is something sane and instances of
> + * "struct wl_interface" are never statically allocated, older software should
> + * still complie and link against newer versions of libwayland.
> + */
>  struct wl_interface {
>  	const char *name;
> -	int version;
> +	uint32_t version;
>  	int method_count;
>  	const struct wl_message *methods;
>  	int event_count;
>  	const struct wl_message *events;
> +
> +	/* Added in version 1 */
> +	wl_interface_dispatcher_func_t method_dispatcher;
> +	wl_interface_dispatcher_func_t event_dispatcher;
>  };
>  
>  struct wl_object {
>  	const struct wl_interface *interface;
> -	void (* const * implementation)(void);
> +	const void *implementation;
>  	uint32_t id;
>  };

Hi Jason,

the comment above makes me a little worried. We do have struct
wl_interface statically allocated in both server and client code in the
weston repository, for example:
- clients/workspaces-protocol.c
- src/workspaces-protocol.c

These are parts of protocol extensions, that are not provided
by libwayland. The above files are generated by wayland-scanner, of
course.

Doesn't the above change break such programs, that are compiled with
old libwayland and then ran with new libwayland?

Well, I don't think it breaks, because we never allocate or use arrays
of struct wl_interface, right? We only have arrays of pointers to struct
wl_interface, and on every use of a wl_interface you check the version,
so we do not access non-existant fields.

So maybe the comment just needs a little adjustment on how wl_interface
can be allocated. Also, "complie". :-)


Thanks,
pq