[Bug 92153] Account properties notify signals are dispatched before the account property is updated

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=92153

--- Comment #2 from James Smith <smithjd15 at gmail.com> ---
Does the notify fetch the updated property in advance? Because reversing the
order does fix a stale property issue when immediately fetching the property by
the signal, e.g. when fetching the requested presence of a number of accounts
in kci global presence, a stale presence can be brought in on a fresh signal
and taint the global presence for that global presence change. The reason it
doesn't happen every presence change is that the signal property isn't used
anyway and the account property isn't yet changed to the new value and the
current presence has a higher priority than the expected presence, causing the
old presence to be kept. If the stale presence is higher priority when the last
account signals this is how we get a stuck presence. Without this patch it is
assumed that the signal is always right because it has a property attached and
the notify line would seem redundant because it doesn't send any updated
property. I like this approach reversed, because -any- signal comes after -any-
consideration of the corresponding property, especially if the signal is used
to query the property immediately. Either way, I've been using this patch to
fix the global presence issue for a while now, it looks correct and doesn't
seem to have any regressions. I briefly second-guessed also changing the
serviceNameChanged and profileChanged signals, because the above behaviour may
have been relied on so that the account was still adressable by these
properties until the new property was useable and there doesn't seem to be any
reason to rely on these properties to access the account while they are being
changed anyway.


-------- Original message --------
From: bugzilla-daemon at freedesktop.org 
Date: 11-02-2015  11:42 AM  (GMT-07:00) 
To: smithjd15 at gmail.com 
Subject: [Bug 92153] Account properties notify signals are dispatched before
  the account property is updated 

Comment # 1 on bug 92153 from David Edmundson
I'm not sure I understand

parent->notify just emits propertyChanged("propertyName")


 * Notify that a property named \a propertyName changed.
 *
 * This method will emit propertyChanged() for \a propertyName.
 *
 * \todo Use for more classes beyond Account. Most importantly Contact.
 */
void Object::notify(const char *propertyName)
{
    emit propertyChanged(QLatin1String(propertyName));
}


As far as I can tell, the only user of this is AccountSet and some unit tests.

git grep propertyChanged
TelepathyQt/account-set.cpp:            SIGNAL(propertyChanged(QString)),
TelepathyQt/object.cpp: * This method will emit propertyChanged() for \a
propertyName.
TelepathyQt/object.cpp:    emit propertyChanged(QLatin1String(propertyName));
TelepathyQt/object.h:    void propertyChanged(const QString &propertyName);
tests/dbus/account-connection-factory.cpp:               
SIGNAL(propertyChanged(QString)),
tests/dbus/account-connection-factory.cpp:               
SIGNAL(propertyChanged(QString)),


As for requested presence; it's set on line 4466 and the emit is on line 4470,
so that's always set before the emit.
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