[PATCH wayland] doc: Document behavior of non-nullable object arguments in clients

[Pekka Paalanen]

On Wed, 24 Jan 2018 14:28:15 +0100
Philipp Kerling <pkerling at casix.org> wrote:

> ---
>  src/wayland-util.h | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/src/wayland-util.h b/src/wayland-util.h
> index caeac82..b6cbe0e 100644
> --- a/src/wayland-util.h
> +++ b/src/wayland-util.h
> @@ -78,12 +78,23 @@ extern "C" {
>   * wl_message is to a protocol message like a class is to an object.
>   *
>   * The `name` of a wl_message is the name of the corresponding protocol message.
> + *
>   * The `signature` is an ordered list of symbols representing the data types
>   * of message arguments and, optionally, a protocol version and indicators for
>   * nullability. A leading integer in the `signature` indicates the _since_
>   * version of the protocol message. A `?` preceding a data type symbol indicates
> - * that the following argument type is nullable. When no arguments accompany a
> - * message, `signature` is an empty string.
> + * that the following argument type is nullable. While it is a protocol violation
> + * to send messages with non-nullable arguments set to `NULL`, event handlers in
> + * clients might still get called with non-nullable object arguments set to
> + * `NULL`. This can happen when the client destroyed the object being used as
> + * argument on its side and an event referencing that object was sent before the
> + * server knew about its destruction. As this race cannot be prevented, clients
> + * should - as a general rule - program their event handlers such that they can
> + * handle object arguments declared non-nullable being `NULL` gracefully.
> + *
> + * When no arguments accompany a message, `signature` is an empty string.
> + *
> + * Symbols:
>   *
>   * * `i`: int
>   * * `u`: uint

Looks good, pushed:
   e5b52f6..ef48ff2  master -> master

Next time remember the S-o-b, please. :-)


Thanks,
pq
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