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# QAxBindable Class Reference
[QAxServer module]

The QAxBindable class provides an interface between a QWidget and an ActiveX client. More...

     #include <QAxBindable>

- List of all members, including inherited members

### Public Functions

- QAxBindable ()
- virtual ~QAxBindable ()
- virtual QAxAggregated * createAggregate ()
- virtual bool readData ( QIODevice * source, const QString & format )
- void reportError ( int code, const QString & src, const QString & desc, const QString & context = QString() )
- virtual bool writeData ( QIODevice * sink )

### Protected Functions

- IUnknown * clientSite () const
- void propertyChanged ( const char * property )
- bool requestPropertyChange ( const char * property )

## Detailed Description

The QAxBindable class provides an interface between a QWidget and an ActiveX client.

The functions provided by this class allow an ActiveX control to communicate property changes to a client application. Inherit your control class from both QWidget (directly or indirectly) and this class to get access to this class's functions. The meta-object compiler requires you to inherit from QWidget first.

     class MyActiveX : public QWidget, public QAxBindable
     {
         Q_OBJECT
         Q_PROPERTY(int value READ value WRITE setValue)

     public:
         MyActiveX(QWidget *parent = 0);
         ...

         int value() const;
         void setValue(int);
     };

When implementing the property write function, use requestPropertyChange() to get permission from the ActiveX client application to change this property. When the property changes, call propertyChanged() to notify the ActiveX client application about the change. If a fatal error occurs in the control, use the static reportError() function to notify the client.

Use the interface returned by clientSite() to call the ActiveX client. To implement additional COM interfaces in your ActiveX control, reimplement createAggregate() to return a new object of a QAxAggregated subclass.

The ActiveQt OpenGL example shows how to use QAxBindable to implement additional COM interfaces.

See also QAxAggregated, QAxFactory, and ActiveQt Framework.

## Member Function Documentation

### QAxBindable::QAxBindable ()

Constructs an empty QAxBindable object.

### QAxBindable::~QAxBindable () `[virtual]`

Destroys the QAxBindable object.

### IUnknown * QAxBindable::clientSite () const `[protected]`

Returns a pointer to the client site interface for this ActiveX object, or null if no client site has been set.

Call `QueryInterface()` on the returned interface to get the interface you want to call.

### QAxAggregated * QAxBindable::createAggregate () `[virtual]`

Reimplement this function when you want to implement additional COM interfaces in the ActiveX control, or when you want to provide alternative implementations of COM interfaces. Return a new object of a QAxAggregated subclass.

The default implementation returns the null pointer.

### void QAxBindable::propertyChanged ( const char * property ) `[protected]`

Call this function to notify the client that is hosting this ActiveX control that the property property has been changed.

This function is usually called at the end of the property's write function.

See also requestPropertyChange().

### bool QAxBindable::readData ( QIODevice * source, const QString & format ) `[virtual]`

If the COM object supports a MIME type then this function is called to initialize the COM object from the data source in format. You have to open source for reading before you can read from it.

Returns true to indicate success. If the function returns false, then ActiveQt will process the data by setting the properties through the meta object system.

If you reimplement this function you also have to implement writeData(). The default implementation does nothing and returns false.

Warning: ActiveX controls embedded in HTML can use either the `type` and `data` attribute of the `object` tag to read data, or use a list of `param` tags to initialize properties. If `param` tags are used, then Internet Explorer will ignore the `data` attribute, and readData will not be called.

This function was introduced in Qt 4.1.

See also writeData().

### void QAxBindable::reportError ( int code, const QString & src, const QString & desc, const QString & context = QString() )

Reports an error to the client application. code is a control-defined error code. desc is a human-readable description of the error intended for the application user. src is the name of the source for the error, typically the ActiveX server name. context can be the location of a help file with more information about the error. If context ends with a number in brackets, e.g. [12], this number will be interpreted as the context ID in the help file.

### bool QAxBindable::requestPropertyChange ( const char * property ) `[protected]`

Call this function to request permission to change the property property from the client that is hosting this ActiveX control. Returns true if the client allows the change; otherwise returns false.

This function is usually called first in the write function for property, and writing is abandoned if the function returns false.

     void MyActiveQt::setText(const QString &text)
     {
         if (!requestPropertyChange("text"))
             return;

         // update property

         propertyChanged("text");
     }

See also propertyChanged().

### bool QAxBindable::writeData ( QIODevice * sink ) `[virtual]`

If the COM object supports a MIME type then this function is called to store the COM object into sink. You have to open sink for writing before you can write to it.

Returns true to indicate success. If the function returns false, then ActiveQt will serialize the object by storing the property values.

If you reimplement this function you also have to implement readData(). The default implementation does nothing and returns false.

This function was introduced in Qt 4.1.

See also readData().