Hi, I was working on another delegate that doesn't need icon to learn and I saw another problem:
the QListView with this delegate doesn't show the selected items. when you click on the item the signal slot that I set for it activates but the item doesn't get selected. what should I do about that?

Let Qt do the actual drawing of all the stuff except the icon and the text:

void MyItemDelegate::paint(QPainter *painter,
        const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    QStyleOptionViewItemV4 opt = option;
    initStyleOption(&opt, index);
    opt.icon = QIcon();
    opt.text = QString();

    const QWidget *widget = option.widget;
    QStyle *style = widget ? widget->style() : QApplication::style();
    style->drawControl(QStyle::CE_ItemViewItem, &opt, painter, widget);

    // draw icon and text
    ....
}

struct TrackDelegate: public QStyledItemDelegate
{
TrackDelegate(QObject* parent = NULL) : QStyledItemDelegate(parent) {}

void paint(QPainter* p, const QStyleOptionViewItem& o, const QModelIndex& idx) const override
{
    // get the data from the index
    QString track  = idx.data(Qt::UserRole+2).toString();
    QString artist = idx.data(Qt::UserRole+6).toString();
    QString title = idx.data(Qt::UserRole+3).toString();

    QRect trackRect  = o.rect.adjusted(0, 0, 30, o.rect.height());
    QRect titleRect = o.rect.adjusted(40, 0, o.rect.width(), o.rect.height()/2);
    QRect artistRect = o.rect.adjusted(40, o.rect.height()/2, o.rect.width(), o.rect.height());

    //draw the data in their rectangles
    p->drawText(trackRect, Qt::AlignLeft, track);
    p->drawText(artistRect, Qt::AlignLeft, artist);
    p->drawText(titleRect, Qt::AlignLeft, title);
}

QSize sizeHint(const QStyleOptionViewItem& o, const QModelIndex& idx) const override
{
    //get the default size hint
    QSize sh = QStyledItemDelegate::sizeHint(o, idx);
    //modify the hint to fit 2 lines of text
    return QSize(sh.width(), sh.height());
}

};

#ifndef ALBUMDELEGATE
#define ALBUMDELEGATE

#include <QMainWindow>
#include <QRect>
#include <QStyledItemDelegate>
#include <QPainter>

struct AlbumDelegate: public QStyledItemDelegate
{
AlbumDelegate(QObject* parent = NULL) : QStyledItemDelegate(parent) {}

void paint(QPainter* p, const QStyleOptionViewItem& o, const QModelIndex& idx) const override
{
    // get the data from the index
    QString title  = idx.data(Qt::UserRole+2).toString();
    QString artist = idx.data(Qt::UserRole+3).toString();
    QIcon icon = idx.data(Qt::DecorationRole).value<QIcon>();

    //split cell rectangle into upper and lower half
    //QRect titleRect  = o.rect.adjusted(0, 0, 0, -o.rect.height()/2);
    //QRect artistRect = o.rect.adjusted(0, o.rect.height()/2, 0, 0);

    QRect iconRect = o.rect.adjusted(0, 0, o.rect.width(), o.rect.height()-40);
    QRect titleRect  = o.rect.adjusted(0, o.rect.height()-40, o.rect.width(), o.rect.height()-20);
    QRect artistRect = o.rect.adjusted(0, o.rect.height()-20, o.rect.width(), o.rect.height());

    //draw the data in their rectangles
    p->drawPixmap(iconRect, icon.pixmap(o.rect.width(), o.rect.width()),o.rect);
    p->drawText(titleRect, Qt::AlignLeft, title);
    p->drawText(artistRect, Qt::AlignLeft, artist);
}

QSize sizeHint(const QStyleOptionViewItem& o, const QModelIndex& idx) const override
{
    //get the default size hint
    QSize sh = QStyledItemDelegate::sizeHint(o, idx);
    //modify the hint to fit 2 lines of text
    return QSize(sh.width(), sh.height()*2);
}

};

#endif // ALBUMDELEGATE

and also I have set shortcuts to resize icons of items by triggreing them. I want those to work properly.
What should I do?