[PATCH weston v5 15/36] libweston: add weston_head destroy signal

[Derek Foreman]

On 2017-12-14 05:40 AM, Pekka Paalanen wrote:
> From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> 
> Add support for subscribing to weston_head destruction.
> 
> The primary use case for heads being destroyed arbitrarily is the
> DRM-backend with MST connectors, which may disappear on unplug. It is
> not just the connector becoming disconnected, it is the connector
> actually disappearing.
> 
> The compositor needs to know about disappearing heads so that it has a
> chance to clean up "orphaned" outputs which do get disabled but still
> need destroying at run time. Shutdown would destroy them as well.
> 
> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> ---
>   libweston/compositor.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>   libweston/compositor.h |  9 +++++++++
>   2 files changed, 54 insertions(+)
> 
> diff --git a/libweston/compositor.c b/libweston/compositor.c
> index a43ee277..86efcfad 100644
> --- a/libweston/compositor.c
> +++ b/libweston/compositor.c
> @@ -4433,6 +4433,7 @@ weston_head_init(struct weston_head *head, const char *name)
>   	memset(head, 0, sizeof *head);
>   
>   	wl_list_init(&head->compositor_link);
> +	wl_signal_init(&head->destroy_signal);
>   	wl_list_init(&head->output_link);
>   	wl_list_init(&head->resource_list);
>   	head->name = strdup(name);
> @@ -4701,6 +4702,8 @@ weston_head_detach(struct weston_head *head)
>   WL_EXPORT void
>   weston_head_release(struct weston_head *head)
>   {
> +	wl_signal_emit(&head->destroy_signal, head);
> +
>   	weston_head_detach(head);
>   
>   	free(head->make);
> @@ -4893,6 +4896,48 @@ weston_head_get_output(struct weston_head *head)
>   	return head->output;
>   }
>   
> +/** Add destroy callback for a head
> + *
> + * \param head The head to watch for.
> + * \param listener The listener to add. The \c notify member must be set.
> + *
> + * Heads may get destroyed for various reasons by the backends. If a head is
> + * attached to an output, the compositor should listen for head destruction
> + * and reconfigure or destroy the output if necessary.
> + *
> + * The destroy callbacks will be called on weston_head destruction before any
> + * automatic detaching from an associated weston_output and before any
> + * weston_head information is lost.
> + *
> + * The \c data argument to the notify callback is the weston_head being
> + * destroyed.
> + */
> +WL_EXPORT void
> +weston_head_add_destroy_listener(struct weston_head *head,
> +				 struct wl_listener *listener)
> +{
> +	wl_signal_add(&head->destroy_signal, listener);
> +}

Sure, and we don't need a remove_destroy_listener because the caller 
would still have the listener and would just 
wl_list_remove(&listener.link) or similar...

This looks good to me
Reviewed-by: Derek Foreman <derekf at osg.samsung.com>

> +/** Look up destroy listener for a head
> + *
> + * \param head The head to query.
> + * \param notify The notify function used used for the added destroy listener.
> + * \return The listener, or NULL if not found.
> + *
> + * This looks up the previously added destroy listener struct based on the
> + * notify function it has. The listener can be used to access user data
> + * through \c container_of().
> + *
> + * \sa wl_signal_get()
> + */
> +WL_EXPORT struct wl_listener *
> +weston_head_get_destroy_listener(struct weston_head *head,
> +				 wl_notify_func_t notify)
> +{
> +	return wl_signal_get(&head->destroy_signal, notify);
> +}
> +
>   /* Move other outputs when one is resized so the space remains contiguous. */
>   static void
>   weston_compositor_reflow_outputs(struct weston_compositor *compositor,
> diff --git a/libweston/compositor.h b/libweston/compositor.h
> index f9d034c3..af61215e 100644
> --- a/libweston/compositor.h
> +++ b/libweston/compositor.h
> @@ -155,6 +155,7 @@ enum dpms_enum {
>   struct weston_head {
>   	struct weston_compositor *compositor;	/**< owning compositor */
>   	struct wl_list compositor_link;	/**< in weston_compositor::head_list */
> +	struct wl_signal destroy_signal;	/**< destroy callbacks */
>   
>   	struct weston_output *output;	/**< the output driving this head */
>   	struct wl_list output_link;	/**< in weston_output::head_list */
> @@ -2049,6 +2050,14 @@ weston_head_get_output(struct weston_head *head);
>   void
>   weston_head_detach(struct weston_head *head);
>   
> +void
> +weston_head_add_destroy_listener(struct weston_head *head,
> +				 struct wl_listener *listener);
> +
> +struct wl_listener *
> +weston_head_get_destroy_listener(struct weston_head *head,
> +				 wl_notify_func_t notify);
> +
>   struct weston_head *
>   weston_compositor_iterate_heads(struct weston_compositor *compositor,
>   				struct weston_head *iter);
>