QT QDeclarativeImageProvider child class single instance?

[tkastlunger]

Hi,
has someone else seen this?
I have a

class QMyImgProvClass : public QDeclarativeImageProvider{
..
virtual QImage requestImage(const QString &id, QSize *size, const QSize& requestedSize){
...
}
QMyImgProvClass * instance(){
static QMyImgProvClass s_myClass;
return &s_myClass;
}
public:
QList<int> m_list;
};

Since I need to use this in a plugin, I register it in the

void BookmarkModelPluginPlugin::initializeEngine(QDeclarativeEngine *engine, const char *uri){
engine->addImageProvider(QLatin1String(MY_IMGPROV_NAME), QMyImgProvClass::Instance());
}

through a simple Singleton.

In the plugin then, I populate the m_list;
.
Now, the requestImage is called correctly from QML. BUT, the effect is that the m_list list is EMPTY for each call. It seems that for each call to the requestImage, the "this" pointer is different.

I thought the addImageProvider registers a single object as an image provider?

[Villep]

Are you populating m_list before opening any QML file?

Br,
Villep

[tkastlunger]

From inside ::componentComplete of the plugin.

[Villep]

What ::componentComplete are you referring to? Component.onCompleted inside QML? How are you trying to populate m_list, C++ side or inside some QML file?

Br,
Villep

[tkastlunger]

From inside ::componentComplete of the plugin.

How would I be able to populate the plugin from QML with C++? Would be intresting to know .

[Villep]

How are you calling ::componentComplete? You can also try adding some variable in your that you increment each time requestImage is called to make sure it gets incremented with a single instance.
Something like

#include <QDebug>

class QMyImgProvClass : public QDeclarativeImageProvider {
public:
    QMyImgProvClass() : mNumberOfCalls(0)
    {   
    }    
    ...
    virtual QImage requestImage(const QString &id, QSize *size, const QSize& requestedSize){
        ...
        ++mNumberOfCalls;
        
        qDebug() << "Calls:" << mNumberOfCalls; 
    }

public:
    QList<int> m_list;

private:
    int mNumberOfCalls;
};

Br,
Villep

[tkastlunger]

::componentComplete is called by the QML backend, I personally do not call it directly.
The strange thing is that the list _is_ populated, if I access it through the singleton. If I access it from within the requestImage, as in:

virtual QImage requestImage(const QString &id, QSize *size, const QSize& requestedSize){
...
if (m_list.size() > 0)
// this is never reached because m_list is empty

}

whilst this in turn:

virtual QImage requestImage(const QString &id, QSize *size, const QSize& requestedSize){
...
if (QMyImgProvClass::Instance().m_list.size() > 0)
// this is reached just fine.

}