Q_DECLARE_METATYPE and qVariantCanConvert

[manojmka]

Hi,

I have the following class in a static lib:

class ITGraphic : public QPixmap
{
 ....
....
};
 
Q_DECLARE_METATYPE(ITGraphic);

class ITGraphic : public QPixmap
{
 ....
....
};

Q_DECLARE_METATYPE(ITGraphic);

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Thereafter I am returning ITGraphic object in another static library from model class in data function:

QVariant ITPictureList::data(const QModelIndex &index, int role) const
{
	if (!index.isValid())
		return QVariant();
 
	if (role == Qt::DecorationRole)
	{
		ITGraphic *graphic = GetBitmap(index.row());
		if(graphic != NULL)
		{
			QPixmap tmpPixmap = graphic->scaled(iconSize,Qt::KeepAspectRatio);
			return QIcon(tmpPixmap);
		}
		else
			return QVariant();
	}
	else if (role == Qt::UserRole)
	{
		return *(GetBitmap(index.row()));
	}
 
	return QVariant();
}

QVariant ITPictureList::data(const QModelIndex &index, int role) const
{
	if (!index.isValid())
		return QVariant();
		
	if (role == Qt::DecorationRole)
	{
		ITGraphic *graphic = GetBitmap(index.row());
		if(graphic != NULL)
		{
			QPixmap tmpPixmap = graphic->scaled(iconSize,Qt::KeepAspectRatio);
			return QIcon(tmpPixmap);
		}
		else
			return QVariant();
	}
	else if (role == Qt::UserRole)
	{
		return *(GetBitmap(index.row()));
	}
	
	return QVariant();
}

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I am trying to get this object like this:

QVariant value = picList->data(index,Qt::UserRole);

res = qVariantCanConvert<ITGraphic>(value);
ITGraphic pGraphic = qvariant_cast<ITGraphic>(value);

res = qVariantCanConvert<ITGraphic>(value);
ITGraphic pGraphic = qvariant_cast<ITGraphic>(value);

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qVariantCanConvert returns false here and I am not able to get the proper object here. But if I try the following, it works:

QPixmap pGraphic = qVariantValue<QPixmap>(picList->data(index, Qt::UserRole));

QPixmap pGraphic = qVariantValue<QPixmap>(picList->data(index, Qt::UserRole));

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Can someone help me, how to get the ITGraphic object here?

Regards,
Manoj

[manojmka]

I finally found the solution to this myself. There are two possible solutions to this:

(1) Implementing a copy constructor for ITGraphic class and then it should start work.

(2) I did it other way round and changed the data function as follows:

QVariant ITPictureList::data(const QModelIndex &index, int role) const
{
	if (!index.isValid())
		return QVariant();
 
	if (role == Qt::DecorationRole)
	{
		ITGraphic *graphic = GetBitmap(index.row());
		if(graphic != NULL)
		{
			QPixmap tmpPixmap = graphic->scaled(iconSize,Qt::KeepAspectRatio);
			return QIcon(tmpPixmap);
		}
		else
			return QVariant();
	}
	else if(role == Qt::DisplayRole)
		return GetFileName(index.row());
	else if (role == Qt::UserRole)
	{
		ITGraphic *graphic = GetBitmap(index.row());
		QVariant v;
		qVariantSetValue(v,graphic);
		return v;
	}
	else if (role == Qt::ToolTipRole)
		return GetFilePathName(index.row());
 
	return QVariant();
}

QVariant ITPictureList::data(const QModelIndex &index, int role) const
{
	if (!index.isValid())
		return QVariant();
		
	if (role == Qt::DecorationRole)
	{
		ITGraphic *graphic = GetBitmap(index.row());
		if(graphic != NULL)
		{
			QPixmap tmpPixmap = graphic->scaled(iconSize,Qt::KeepAspectRatio);
			return QIcon(tmpPixmap);
		}
		else
			return QVariant();
	}
	else if(role == Qt::DisplayRole)
		return GetFileName(index.row());
	else if (role == Qt::UserRole)
	{
		ITGraphic *graphic = GetBitmap(index.row());
		QVariant v;
		qVariantSetValue(v,graphic);
		return v;
	}
	else if (role == Qt::ToolTipRole)
		return GetFilePathName(index.row());
	
	return QVariant();
}

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Then getting the data like this:

ITGraphic *pGraphic = qVariantValue<ITGraphic*>(picList->data(index,Qt::UserRole));

ITGraphic *pGraphic = qVariantValue<ITGraphic*>(picList->data(index,Qt::UserRole));

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It works!! :-)

Regards,
Manoj