Unable to get CloudProviders signals from DBus

Platform
#1

Hello everyone,

I’m trying to use the libcloudproviders DBus API in a shell extension I’m writing.

However, I can’t get signals from DBus. Specifically, the InterfacesAdded and InterfacesRemoved signals from the ObjectManager interface (which should be emitted when a provider or an account is added or removed) and the g-properties-changed signal on accounts objects (which should be emitted when the status of an account changes).

To test this, I’m using the Nextcloud client, and adding/removing folder syncs (that should send the InterfacesAdded and InterfacesRemoved signals) and putting/deleting files in these folders (that should send the g-properties-changed signal). I can see the values changing in D-Feet, but can’t get any signal.

Here’s my code for the ObjectManager:

const { Gio } = imports.gi;

const OBJECT_MANAGER_INTERFACE = `
<node>
    <interface name="org.freedesktop.DBus.ObjectManager">
        <method name="GetManagedObjects">
            <arg type="a{oa{sa{sv}}}" name="object_paths_interfaces_and_properties" direction="out"/>
        </method>
        <signal name="InterfacesAdded">
            <arg type="o" name="object_path"/>
            <arg type="a{sa{sv}}" name="interfaces_and_properties"/>
        </signal>
        <signal name="InterfacesRemoved">
            <arg type="o" name="object_path"/>
            <arg type="as" name="interfaces"/>
        </signal>
    </interface>
</node>`;

function enable() {
    const ObjectManagerProxy = Gio.DBusProxy.makeProxyWrapper(OBJECT_MANAGER_INTERFACE);
    const objectManagerProxy = new ObjectManagerProxy(
        Gio.DBus.session,
        'com.nextcloudgmbh.Nextcloud',
        '/com/nextcloudgmbh/Nextcloud'
    );
    objectManagerProxy.connectSignal('InterfacesAdded', () => log('Interfaces added'));
    objectManagerProxy.connectSignal('InterfacesRemoved', () => log('Interfaces removed'));
}

And the one for listening to an account:

const { Gio } = imports.gi;

const CLOUDPROVIDERS_ACCOUNT_INTERFACE = `
<node>
    <interface name="org.freedesktop.CloudProviders.Account">
        <property type="s" name="Name" access="read"/>
        <property type="s" name="Path" access="read"/>
        <property type="s" name="Icon" access="read"/>
        <property type="i" name="Status" access="read"/>
        <property type="s" name="StatusDetails" access="read"/>
    </interface>
</node>`;

function enable() {
    const AccountProxy = Gio.DBusProxy.makeProxyWrapper(CLOUDPROVIDERS_ACCOUNT_INTERFACE);
    const accountProxy = new AccountProxy(
        Gio.DBus.session,
        'com.nextcloudgmbh.Nextcloud',
        '/com/nextcloudgmbh/Nextcloud/Folder/0'
    );
    accountProxy.connect('g-properties-changed', () => log('Properties changed'));
}

I tried this on other DBus interfaces, and I get signals. Is there anything I’m missing here? Or do you think it is something not happening in libcloudproviders?

#2

Probably not the cause of your problems but gio does actually have Gio.DBusObjectManagerClient

#3

Thank you, I tried listening to all the implemented signals on Gio.DBusObjectManagerClient with the following code:

const { Gio } = imports.gi;

function enable() {
    const client = Gio.DBusObjectManagerClient.new_sync(
        Gio.DBus.session,
        Gio.DBusObjectManagerClientFlags.NONE,
        'com.nextcloudgmbh.Nextcloud',
        '/com/nextcloudgmbh/Nextcloud',
        null,
        null
    );
    client.connect('interface-added', () => log('interface-added'));
    client.connect('interface-removed', () => log('interface-removed'));
    client.connect('object-added', () => log('object-added'));
    client.connect('object-removed', () => log('object-removed'));
    client.connect('interface-proxy-properties-changed', () => log('interface-proxy-properties-changed'));
    client.connect('interface-proxy-signal', () => log('interface-proxy-signal'));
}

But again nothing seems to be emitted when adding or removing folder syncs.

What’s strange is that when I close and open the session, the interface-proxy-properties-changed and g-properties-changed are each emitted twice, but after that nothing is emitted even if I can see things changing in D-Feet.

#4

After some fiddling I managed to get signals with a very strange change: I need to initialize the variable storing the proxy globally.

let accountProxy;
function enable() {
    const AccountProxy = Gio.DBusProxy.makeProxyWrapper(CLOUDPROVIDERS_ACCOUNT_INTERFACE);
    accountProxy = new AccountProxy(
        Gio.DBus.session,
        'com.nextcloudgmbh.Nextcloud',
        '/com/nextcloudgmbh/Nextcloud/Folder/0'
    );
    accountProxy.connect('g-properties-changed', () => log('Properties changed'));
}

I then get all the signals. But if I initialize the variable just before creating the proxy (inside the enable function), I get some signals but it also misses others. And if I initialize the variable with the proxy, I don’t get anything.

I really have no clue about what’s causing this behavior, is this expected?

#5

In your code samples above the proxy is being garbage collected when the function enable() returns, since the variable is in the function’s scope.

#6

Thank you, that would be the explanation!

I guess that with the other proxies that seemed to work without storing them globally, I had simply been lucky and managed to get signals before they were garbage collected?

#7

More likely you were holding a reference elsewhere, or the signals were emitted as a result of something synchronous and thus the callbacks were invoked before the function returned.

There is a short guide called Tips on Memory Management in the GNOME Wiki that covers some of the basics that related to GJS and GObjects.

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#8

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