Hello,
I try to connect the DBus PropertiesChanged Signal with Qt and
PySide6/Python, the signal has the following signature:
org.freedesktop.DBus.Properties.PropertiesChanged (STRING interface_name,
ARRAY of
DICT_ENTRY<STRING,VARIANT> changed_properties,
ARRAY<STRING> invalidated_properties);
Concrete I need the signal and PropertiesChanged metadata of the MPRIS
standard (https://specifications.freedesktop.org/mpris-spec/latest/,
https://www.freedesktop.org/wiki/Specifications/mpris-spec/metadata/),
the meta data has a dictionary in the propertieschanged dictionary and
the inner dictionary has arrays as values on some entries, I can see the
data by setting the environment variable "QDBUS_DEBUG": "1" or on a
cross check using sdbus:
('org.mpris.MediaPlayer2.Player',
{'Metadata': ('a{sv}', {'xesam:albumArtist': ('as', ['Daft Punk',
'Pharrell Williams', 'Nile Rodgers']),
'mpris:trackid': ('o',
'/spotify/track/2Foc5Q5nqNiosCNqttzHof'),
'xesam:title': ('s', 'Get Lucky (Radio Edit) [feat.
Pharrell Williams and Nile Rodgers]'),
'xesam:album': ('s', 'Get Lucky (Radio Edit) [feat.
Pharrell Williams and Nile Rodgers]'),
'xesam:trackNumber': ('u', 1), 'xesam:discNumber': ('i', 1),
'mpris:artUrl': ('s',
'https://i.scdn.co/image/ab67616d0000b2731d5cf960a92bb8b03fc2be7f'),
'xesam:url': ('s',
'https://open.spotify.com/track/2Foc5Q5nqNiosCNqttzHof'),
'mpris:length': ('x', 248413000), 'xesam:autoRating': ('d',
0.82),
'xesam:artist': ('as', ['Daft Punk', 'Pharrell Williams',
'Nile Rodgers'])}),
'PlaybackStatus': ('s', 'Playing')},
[])
I test it currently with the DBus NetworkManager, it is simpler as it
has no inner dictionary, but some arrays of objects as value and I can
force the signal by enabling and disabling my network connection on
Ubuntu, these are 2 example outputs:
('org.freedesktop.NetworkManager', {'ActiveConnections': ('ao',
['/org/freedesktop/NetworkManager/ActiveConnection/8'])}, [])
('org.freedesktop.NetworkManager', {'State': ('u', 40)}, [])
But for neither of the 2 I can't get the connected slot method to run, I
also don't get any error.
I managed to connect to DBus signals with simple data types, but I can't
get it to work with PropertiesChanged, whith the dictionaries and arrays.
I have uploaded demos on github with a Visual Studio Code project:
https://github.com/Drexel2k/qdbus
This is the NetworkManager demo I want to get to work first:
https://github.com/Drexel2k/qdbus/blob/main/qdbusdemo_netmanpropertieschanged.py
This is a working cross check with sdbus:
https://github.com/Drexel2k/qdbus/blob/main/sdbusdemo.py
This is a working demo with the simple data types:
https://github.com/Drexel2k/qdbus/blob/main/qdbusdemo_dbusnameownerchanged.py
For all of the 3 a debug config exists, currently for the Qt modules the
QDBUS_DEBUG environment variable is set to 0, but it can be easily
enabled by setting it to 1.
The documentation (https://doc.qt.io/qt-6/qdbustypesystem.html) also says:
Extending the Type System
In order to use one's own type with Qt D-Bus, the type has to be
declared as a Qt meta-type with the Q_DECLARE_METATYPE() macro and
registered with the qDBusRegisterMetaType() function. The streaming
operators operator>> and operator<< will be automatically found by the
registration system.
and:
Warning: You may not use any type that is not on the list above,
including typedefs to the types listed. This also includes
QList<QVariant> and QMap<QString,QVariant>.
I saw some C++ examples also using QDBusArgument and overloading the
streaming operators, I don't know if this would be the solution, but I
also don't know how to do this in Python.
Any help is appreciated, thank you in advance!
Best regards
Matthias
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