qdbusxml2cpp generated properties with NOTIFY signals

greenroom

First, it seems that qdbusxml2cpp does not generate NOTIFY signals. Is there a way to get it to do that? Being able to specify a signal with an annotation of some kind seems reasonable. Is there a technical reason why this is not available? This seems like a fairly large gap in DBus and QML integration. As it is, we will likely have to hand code our QDbusAbstractInterface classes, rather than using those generated by qdbusxml2cpp.

greenroom

@greenroom Here is an example to make my question more clear: given the following DBus interface xml

<!--
           SpeedRpm
           The current handpiece speed in RPM.
-->
<property name="speedRpm" type="q" access="read"/>

the following code is generated

Q_PROPERTY(ushort speedRpm READ speedRpm)
inline ushort speedRpm() const
{ return qvariant_cast< ushort >(property("speedRpm")); }

Why can't qdbusxml2cpp generate this code

Q_PROPERTY(ushort speedRpm READ speedRpm NOTIFY speedRpmChanged)
inline ushort speedRpm() const
{ return qvariant_cast< ushort >(property("speedRpm")); }
...
signals:
void speedRpmChanged(ushort speed);

SGaist

Hi,

Just an educated guess: there's no reason from your description to add a signal. You have a read only property. If you want to have an additional signal then your interface declaration should state that as well.

Not all Qt properties have notification signal.

greenroom

@SGaist I will add some more context to make the use case more clear. The goal is to use this interface from QML. For example,

Text {
        id: speedText
        text:  HpA.speedRpm
...
}

So, in this case we need the NOTIFY signal.

SGaist

I understand you need. What I am saying is that you likely need to make your interface declaration more complete in order for the notify signal to be generated.

greenroom

@SGaist said in qdbusxml2cpp generated properties with NOTIFY signals:

make your interface declaration more complete

I am sorry, I don't understand what you mean. What is it missing?

SGaist

It's missing the signal part.

muman

Has anyone figured out a way to get qdbusxml2cpp to generated properties with the NOTIFY signal?

I have an interface which I defined and it expressly says that the property has a change signal, but when I create an XML from it and use that XML to generate a proxy class for the interface it does not expose the NOTIFY signal (although the signal is defined with QT_SIGNAL)...

Here is the original Interface Class:

class benchInterface : public QObject {
    Q_OBJECT;
    Q_CLASSINFO("D-Bus Interface", "com.cana.bench")

    Q_PROPERTY(uchar gpioa READ gpioa WRITE setGpioa NOTIFY gpioaChanged)
    Q_PROPERTY(QString state READ getState WRITE setState NOTIFY stateChanged)

  public:
    benchInterface(QObject *parent = nullptr);
    virtual ~benchInterface();

  public slots:
    bool startProcess(QString data);
    void quit();

  signals:
    void processComplete(QString data);
    void processFailed(int errorcode);
    void gpioaChanged();
    void stateChanged();

  private slots:
    void onTimer();

  private:
    uchar gpioa();
    void setGpioa(uchar value);

    void setState(QString newState);
    QString getState();

    QString processData;
    QString state = "Idle";

    std::unique_ptr<cana::interface::i2c::i2c> i2c2_controller;
    std::unique_ptr<MCP23017> mcp23017;
};

So I have a property state which is a QString which has a notify signal stateChanged(). The XML produced from qdbuscpp2xml is :

<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN" "http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
<node>
  <interface name="com.cana.bench">
    <property name="gpioa" type="y" access="readwrite"/>
    <property name="state" type="s" access="readwrite"/>
    <signal name="processComplete">
      <arg name="data" type="s" direction="out"/>
    </signal>
    <signal name="processFailed">
      <arg name="errorcode" type="i" direction="out"/>
    </signal>
    <signal name="gpioaChanged">
    </signal>
    <signal name="stateChanged">
    </signal>
    <method name="startProcess">
      <arg type="b" direction="out"/>
      <arg name="data" type="s" direction="in"/>
    </method>
    <method name="quit">
    </method>
  </interface>
</node>

But the resulting proxy class does not expose the NOTIFY signal:

/*
 * Proxy class for interface com.cana.bench
 */
class ComCanaBenchInterface : public QDBusAbstractInterface {
    Q_OBJECT
  public:
    static inline const char *staticInterfaceName() { return "com.cana.bench"; }

  public:
    ComCanaBenchInterface(const QString &service, const QString &path,
                          const QDBusConnection &connection,
                          QObject *parent = nullptr);

    ~ComCanaBenchInterface();

    Q_PROPERTY(uchar gpioa READ gpioa WRITE setGpioa)
    inline uchar gpioa() const {
        return qvariant_cast<uchar>(property("gpioa"));
    }
    inline void setGpioa(uchar value) {
        setProperty("gpioa", QVariant::fromValue(value));
    }

    Q_PROPERTY(QString state READ state WRITE setState)
    inline QString state() const {
        return qvariant_cast<QString>(property("state"));
    }
    inline void setState(const QString &value) {
        setProperty("state", QVariant::fromValue(value));
    }

  public Q_SLOTS: // METHODS
    inline QDBusPendingReply<> quit() {
        QList<QVariant> argumentList;
        return asyncCallWithArgumentList(QStringLiteral("quit"), argumentList);
    }

    inline QDBusPendingReply<bool> startProcess(const QString &data) {
        QList<QVariant> argumentList;
        argumentList << QVariant::fromValue(data);
        return asyncCallWithArgumentList(QStringLiteral("startProcess"),
                                         argumentList);
    }

  Q_SIGNALS: // SIGNALS
    void gpioaChanged();
    void processComplete(const QString &data);
    void processFailed(int errorcode);
    void stateChanged();
};

Is there something I am missing? When I manually add the NOTIFY to the generated proxy class then the property works correctly (using from QML).

Thank you,
Michael Uman
Sr Firmware Engineer
Cana Technologies

christian.gudrian

Judging from the source code of qdbusxml2cpp: it cannot generate NOTIFY declarations for properties at all.

Christian