Creating custom QItemDelegate with QPushButton in Qt

Recently I was working on Audiobook Reader application for maemo. For this application I have created one custom item delegate for QListView which contains two clickable item and generate signal accordingly.

For application I was using some different mechanism to create button inside custom item delegate, but now I found better way to create custom item delegate with QPushButton. So thought to share code.

Following is code for custom item delegate derived from QItemDelegate.

Update: I have uploaded following code to gitorous, Please visit this link if you want a working sample code.

#include <QItemDelegate>
class CustomItemDelegate : public QItemDelegate
{
    Q_OBJECT
public:
    CustomItemDelegate(QObject *parent = 0);
    virtual void paint(QPainter *painter,
                       const QStyleOptionViewItem &option,
                       const QModelIndex &index) const ;

    virtual QSize sizeHint(const QStyleOptionViewItem &option,
                           const QModelIndex &index) const ;

    bool editorEvent(QEvent *event, QAbstractItemModel *model, 
                           const QStyleOptionViewItem &option, 
                           const QModelIndex &index);

signals:
    void buttonClicked(const QModelIndex &index);
private:
    QStyle::State  _state;
};

#include "customitemdelegate.h"
...

CustomItemDelegate::CustomItemDelegate(QObject *parent) :
    QItemDelegate(parent)
{
    _state =  QStyle::State_Enabled;
}

void CustomItemDelegate::paint(QPainter *painter,
                   const QStyleOptionViewItem &option,
                   const QModelIndex &index) const
{
   const QStandardItemModel* model = 
   static_cast<const QStandardItemModel*>(index.model());
   QStandardItem* item = model->item(index.row());

   QString text = item->text();
   QRect rect = option.rect;

    QRect textRect( rect);
    textRect.setHeight( 30);
    painter->drawText(textRect,text);

    QRect buttonRect( rect);
    buttonRect.setY(textRect.y()+ 35);
    buttonRect.setHeight( 30);
    QStyleOptionButton button;
    button.rect = buttonRect;
    button.text = text;
    button.state = _state | QStyle::State_Enabled;

    QApplication::style()->drawControl
        (QStyle::CE_PushButton, &button, painter);
}

QSize CustomItemDelegate::sizeHint(const QStyleOptionViewItem &/*option*/,
                       const QModelIndex &/*index*/) const
{
    //hard coding size for test purpose, 
    //actual size hint can be calculated from option param
    return QSize(800,70);
}

bool CustomItemDelegate::editorEvent(QEvent *event, 
    QAbstractItemModel *model, 
    const QStyleOptionViewItem &option, 
    const QModelIndex &index)
{
    if( event->type() == QEvent::MouseButtonPress ||
        event->type() == QEvent::MouseButtonRelease ) {
    } else {
         //ignoring other mouse event and reseting button's state
         _state = QStyle::State_Raised;
        return true;
    }

    QRect buttonRect( option.rect);
    buttonRect.setY(option.rect.y()+ 35);
    buttonRect.setHeight( 30);

    QMouseEvent* mouseEvent = static_cast<QMouseEvent*>(event);
    if( !buttonRect.contains( mouseEvent->pos()) ) {
        _state = QStyle::State_Raised;
        return true;
    }

    if( event->type() == QEvent::MouseButtonPress) {            
        _state = QStyle::State_Sunken;
    } else if( event->type() == QEvent::MouseButtonRelease) {
        _state = QStyle::State_Raised;
        emit buttonClicked( index);
    }    
    return true;
}

Basically in above code, I am calculating rect where I want to draw my button and drawing QPushButton on list item using QStyleOptionButton class.

And in editor event on mouse press and release event, I am checking if mouse position on click falls into my button's rect or not. If it falls inside my button's rect then I am emitting signal.

I am using item's signal as shown in below code.

CustomList::CustomList(QWidget *parent) :
    QWidget(parent),_view(0)
{
    _view = new QListView();
    _view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    _view->setEditTriggers(QAbstractItemView::NoEditTriggers);

    //creating custom item delegate and setting  it to view
    CustomItemDelegate* itemDelegate = new CustomItemDelegate(_view);
    _view->setItemDelegate( itemDelegate );

    _view->setModel(&_model); 
   
    //connecting delegate's signal to this class's slot
    connect(itemDelegate,SIGNAL(buttonClicked(QModelIndex)),
    this,SLOT(listButtonClicked(QModelIndex)));

    QHBoxLayout* mainLayout = new QHBoxLayout(this);
    mainLayout->addWidget( _view);

    //creating and adding data to model
    QStandardItem* item = new QStandardItem;
    item->setText("testing");

    QStandardItem* item1 = new QStandardItem;
    item1->setText("testing1");

    _model.appendRow(item);
    _model.appendRow(item1);
}

// following slot will be invoked when delegate's button is clicked
void CustomList::listButtonClicked(const QModelIndex &index)
{
    qDebug() << "######### listbutton clicked ######### " << index.row();
}

Following is snap of how custom item delegate looks.