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
Hi Vinicius,
On Tue, May 3, 2016 at 8:56 PM, Vinicius Costa Gomes <[email protected]> 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