Re: [PATCH BlueZ v2] gdbus: Fix the ordering of signals

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Hi Vinicius,

On Tue, May 3, 2016 at 8:56 PM, Vinicius Costa Gomes <vcgomes@xxxxxxxxx> wrote:
> Consider the following example:
>
> /foo
>   properties: "A", "B"
>
> /bar
>   properties: "C", "D"
>
> If during a given mainloop iteration, property "A" of object '/foo' is
> changed, then properties "C" and "D" of '/bar', lastly "B" of '/foo',
> the current code will emit the PropertiesChanged signals in following
> order: "A", "B", "C", "D".
>
> This may confuse applications that have a dependency on the order of
> those signals.
>
> This fixes the ordering, so in the example, the order becomes:
> "C", "D", "A", B". This is considered not to be a problem, as
> applications may use the flag G_DBUS_PROPERTY_CHANGED_FLAG_FLUSH, so
> property changed signals are emitted as soon as possible.
>
> The solution is for each object, to reschedule the signals every time a
> signal is emitted.
> ---
>  gdbus/gdbus.h  |  9 +++++++++
>  gdbus/object.c | 12 ++++++++++--
>  2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/gdbus/gdbus.h b/gdbus/gdbus.h
> index 69fbc10..e37385f 100644
> --- a/gdbus/gdbus.h
> +++ b/gdbus/gdbus.h
> @@ -302,6 +302,15 @@ void g_dbus_pending_property_error_valist(GDBusPendingReply id,
>                         const char *name, const char *format, va_list args);
>  void g_dbus_pending_property_error(GDBusPendingReply id, const char *name,
>                                                 const char *format, ...);
> +
> +/*
> + * Note that when multiple properties for a given object path are changed
> + * in the same mainloop iteration, they will be grouped with the last
> + * property changed. If this behaviour is undesired, use
> + * g_dbus_emit_property_changed_full() with the
> + * G_DBUS_PROPERTY_CHANGED_FLAG_FLUSH flag, causing the signal to ignore
> + * any grouping.
> + */
>  void g_dbus_emit_property_changed(DBusConnection *connection,
>                                 const char *path, const char *interface,
>                                 const char *name);
> diff --git a/gdbus/object.c b/gdbus/object.c
> index a220101..afb4587 100644
> --- a/gdbus/object.c
> +++ b/gdbus/object.c
> @@ -635,11 +635,19 @@ static gboolean g_dbus_args_have_signature(const GDBusArgInfo *args,
>
>  static void add_pending(struct generic_data *data)
>  {
> -       if (data->process_id > 0)
> -               return;
> +       guint old_id = data->process_id;
>
>         data->process_id = g_idle_add(process_changes, data);
>
> +       if (old_id > 0) {
> +               /*
> +                * If the element already had an old idler, remove the old one,
> +                * no need to re-add it to the pending list.
> +                */
> +               g_source_remove(old_id);
> +               return;
> +       }
> +
>         pending = g_slist_append(pending, data);
>  }
>
> --
> 2.8.1

Applied, thanks


-- 
Luiz Augusto von Dentz
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