On Thu, 19 Sep 2013 13:54:34 +1000
Peter Hutterer <[email protected]> wrote:
> Instead of NULL, a client that doesn't implement all callbacks of a listener
> can use named defines to increase readability of the code. For example:
>
> const struct wl_pointer_listener pointer_listener = {
> WL_POINTER_ENTER_HANDLER_NONE,
> WL_POINTER_LEAVE_HANDLER_NONE,
> motion_handler,
> button_handler,
> axis_handler,
> };
>
> These are defined as typed NULL, so getting the order wrong will yield a
> compiler warning in most cases - at least where neighbouring functions don't
> have the same signature.
>
> #define WL_POINTER_ENTER_HANDLER_NONE \
> ((void(*)(void *, struct wl_pointer *, uint32_t , struct wl_surface *,
> wl_fixed_t , wl_fixed_t )) NULL)
> ---
> Just gathering interest in this, if we want this I'll polish it up and test
> it a bit more.
Hi,
are you sure a NULL handler function pointer is actually legal?
I thought we segfault if it is NULL and the event comes to dispatch.
Or was there some earlier patch that lifted this restriction?
Thanks,
pq
> src/scanner.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/src/scanner.c b/src/scanner.c
> index d02d865..a41da11 100644
> --- a/src/scanner.c
> +++ b/src/scanner.c
> @@ -872,6 +872,23 @@ emit_structs(struct wl_list *message_list, struct
> interface *interface)
> printf("};\n\n");
>
> if (!is_interface) {
> + wl_list_for_each(m, message_list, link) {
> + printf("#define %s_%s_HANDLER_NONE ((void(*)(",
> + interface->uppercase_name, m->uppercase_name);
> + printf("void *, "),
> + printf("struct %s *", interface->name);
> + wl_list_for_each(a, &m->arg_list, link) {
> + printf(", ");
> + if (a->type == OBJECT && a->interface_name == NULL)
> + printf("void *");
> + else if (a->type == NEW_ID)
> + printf("struct %s *", a->interface_name);
> + else
> + emit_type(a);
> + }
> + printf(")) NULL)\n");
> + }
> +
> printf("static inline int\n"
> "%s_add_listener(struct %s *%s,\n"
> "%sconst struct %s_listener *listener, void *data)\n"
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