Problem with QObject::setProperty

[Auliyaa]

Hi everyone,

I'm currently working on a library that defines several types and I want to be able to use them into the Qt's property system.

For instance, I have a ColorButton class containing a "tulipColor" field whose type is tlp::Color:

class TLP_QT_SCOPE ColorButton : public QPushButton {
  Q_OBJECT
  Q_PROPERTY(Color tulipColor READ tulipColor WRITE setTulipColor)
 
  tlp::Color _color;
public:
  explicit ColorButton(QWidget *parent = 0);
 
  Color tulipColor() const;
 
 protected:
  void paintEvent(QPaintEvent *);
 
public slots:
  void setTulipColor(const Color&);
};

class TLP_QT_SCOPE ColorButton : public QPushButton {
  Q_OBJECT
  Q_PROPERTY(Color tulipColor READ tulipColor WRITE setTulipColor)

  tlp::Color _color;
public:
  explicit ColorButton(QWidget *parent = 0);

  Color tulipColor() const;

 protected:
  void paintEvent(QPaintEvent *);

public slots:
  void setTulipColor(const Color&);
};

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I declared the tlp::Color type using the Q_DECLARE_METATYPE macro and the qRegisterMetaType function:

Q_DECLARE_METATYPE(tlp::Color)
// ........
qRegisterMetaType<tlp::Color>("Color");

Q_DECLARE_METATYPE(tlp::Color)
// ........
qRegisterMetaType<tlp::Color>("Color");

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Then I use the following code:

QVariant value = QVariant::fromValue<tlp::Color>(tlp::Color(255,0,0));
  qWarning() << "User Type for value is: " << value.userType();
 
  ColorButton* btn = new ColorButton();
  for (int i=0;i<btn->metaObject()->propertyCount();++i) {
    QMetaProperty prop = btn->metaObject()->property(i);
    qWarning() << "UserType for the " << prop.name() << " property is: " << prop.userType();
  }
 
  btn->setProperty("tulipColor",QVariant::fromValue<tlp::Color>(Color(255,0,0)));
  btn->show();

QVariant value = QVariant::fromValue<tlp::Color>(tlp::Color(255,0,0));
  qWarning() << "User Type for value is: " << value.userType();

  ColorButton* btn = new ColorButton();
  for (int i=0;i<btn->metaObject()->propertyCount();++i) {
    QMetaProperty prop = btn->metaObject()->property(i);
    qWarning() << "UserType for the " << prop.name() << " property is: " << prop.userType();
  }

  btn->setProperty("tulipColor",QVariant::fromValue<tlp::Color>(Color(255,0,0)));
  btn->show();

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And get the following output:

User Type for value is: 258
UserType for the tulipColor property is: 258

So the tulipColor property is correctly registered with a valid userType. But when I try to change the value using the setProperty method, it returns false and my setTulipColor method is never called.

Please help :/

[wysota]

What if you change "Color" to "tlp::Color"?

[Auliyaa]

Using namespace names in Q_PROPERT declarations doesn't sem to compile, I get the same error as related in this bug report: https://bugreports.qt.nokia.com//browse/QTBUG-2151

That's why I tried using Color since my class is in the same namespace. Now if I change qRegisterMetaType<tlp::Color>("Color"); to qRegisterMetaType<tlp::Color>("tlp::Color"); the output of my program becomes:

User Type for value is: 258
UserType for the tulipColor property is: 0

I'm really lost on this one

[Auliyaa]

Help anyone ?