Correctly implementing QStyledItemDelegate

Question

I have a class (EditorTagManager) that contains a QTreeWidget. During runtime, the tree can contain any number of tag items, all of which are checkable. I'm trying to add horizontal lines between the QTreeWidgetItems in order to make it clear that these tags are unrelated and are meant to be separate from one another (each item is a root-level node).

From my research on the subject, I've figured out the only way to control the appearance of QtreeWidgetItems to any meaningful extent is to subclass QStyledItemDelegate and bind the delegate to the QTreeWidget. It's kind of an abstract concept so I don't fully understand it. Since I’ve never had to subclass a Qt object before, I'm not sure if I’m doing it correctly.

Since the Qt Documentation didn't really explain how to do this, I used the settingsdialog.cpp/.h files from the Clementine 1.0.1 source code as my guide/reference because Clementine's preferences window uses similar separators on its QTreeWidget. I'm trying to reverse-engineer my own solution from Clementine's code, the only problem is Clementine's implementation of this does things I don't need (so I have to figure out what's relevant to my code and what's not). That's what got me up to this point; my code is very similar to the Clementine code (I just changed the delegate class name):

Here is my current delegate header declaration in editortreemanager.h:

class TagListDelegate : public QWidget
{

public:
    TagListDelegate(QObject* parent);
    void paint(QPainter* painter, const QStyleOptionViewItem& option,
                const QModelIndex& index) const;
};

Here is my current delegate source in editortreemanager.cpp:

TagListDelegate::TagListDelegate(QObject *parent) :
    TagListDelegate(parent){

}

void TagListDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                            const QModelIndex &index) const{

}

Even though TagListDelegate::paint() doesn't actually do anything yet, I just want to get this code working correctly before I try to change the appearance of the QTreeWidgetItems. My goal is to keep this as simple as possible for now.

Everything compiled fine until I told the QTreeWidget (ui->AvailableTags) to use the delegate:

ui->AvailableTags->setItemDelegate(new TagListDelegate(this)); 

The compiler error reads:

/home/will/qt_projects/robojournal/ui/editortagmanager.cpp:211: error: no matching function for call to 'QTreeWidget::setItemDelegate(TagListDelegate*)'

I’m in a bit over my head here so I would definitely appreciate some help in figuring this out.

UPDATE (7/30/13):

My Delegate class now looks like this:

Source:

TagListDelegate::TagListDelegate(QStyledItemDelegate *parent) :
    TagListDelegate(parent){

}

void TagListDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                            const QModelIndex &index) const{

    QStyledItemDelegate::paint(painter, option, index);

}

Header declaration:

class TagListDelegate : public QStyledItemDelegate
{

public:
    TagListDelegate(QStyledItemDelegate* parent);
    void paint(QPainter* painter, const QStyleOptionViewItem& option,
                const QModelIndex& index) const;
};

UPDATE (7/31/13)

Here is what my classes look like now:

header:

class TagListDelegate : public QStyledItemDelegate
{

public:
    TagListDelegate(QObject* parent);
    QSize sizeHint(const QStyleOptionViewItem& option, const QModelIndex& index) const;
    void paint(QPainter* painter, const QStyleOptionViewItem& option,
                const QModelIndex& index) const;
};

source:

TagListDelegate::TagListDelegate(QObject *parent)
    : TagListDelegate(parent){

}

QSize TagListDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{
     QSize ret = QStyledItemDelegate::sizeHint(option, index);
     return ret;
}


void TagListDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                            const QModelIndex &index) const{

    QStyledItemDelegate::paint(painter, option, index);

}

Answer 1

You're not subclassing QStyledItemDelegate in your code. You're subclassing QWidget. Change

class TagListDelegate : public QWidget

to:

class TagListDelegate : public QStyledItemDelegate

And don't forget to include the header:

#include <QStyledItemDelegate>