Signal for property changes

[Rob Taylor]

Marcel Holtmann wrote:
> Hi Thiago,
> 
>>> So what about adding a signal to the properties introspection that
>>> allows us to do this officially? Something like
>>>
>>>  org.freedesktop.DBus.Properties.Changed (STRING interface_name,
>>>                                           STRING property_name,
>>>                                           VARIANT value);
>>>
>>> Comments?
>> Yes: the signal not being emitted must not mean the property did not 
>> change.
> 
> actually if we have that signal, it should mean exactly that. If you use
> the Set method to change the property, the signal should be emitted. In
> case the property value is changed via a system event or an external
> tool or whatever, the signal should also be emitted. This is the only
> way to keep property values in sync with UI applications without polling
> all the time.
> 
> In case of BlueZ we do exactly this. For example if you use the command
> line tool to change the friendly name (this goes directly via the kernel
> interface) we still send out a signal that the name has changed.
> 
> I can see that in some cases this is not always possible. So what about
> adding that signal, but also having an annotation for the property value
> that indicates that such a signal is available for this property. This
> would also allow backward compatibility with the current specification.


This is pretty much what I was about to propose for use in the D-Bus
version of AT-SPI, so I'll happily help push this along :)

Thanks,
Rob

> Regards
> 
> Marcel
> 
> 
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-- 
Rob Taylor, Codethink Ltd. -  http://codethink.co.uk