QItemDelegate impossible to change text color

[MikhailG]

Trying to make a custom ItemView for a QTreeView. So I subclassed QItemDelegate overrode QItemDelegate::paint and NOTHING!! seems to work I can not change text color as I want it to be at ALL!! Bit if I draw text alone it works. So what do I do not understand?

void MyItemViewDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
    painter->save();

    QStyleOptionViewItem voptCopy(option);
    voptCopy.features |= QStyleOptionViewItemV2::HasDisplay;
    voptCopy.text = index.data(Qt::DisplayRole).toString();

    auto color = index.data(Qt::TextColorRole).value<QColor>();
    painter->setPen(QColor("#FF0000"));
    voptCopy.palette.setColor(QPalette::All, QPalette::Text, QColor("#FF0000"));

    if (m_functor->operator ()(index))
    {
        voptCopy.rect.adjust(-m_indentation, 0, 0, 0);
    }
    else
    {
        voptCopy.rect.adjust(0, 0, 0, 0);
    }

    //painter->drawText(QPoint(voptCopy.rect.x(), voptCopy.rect.y()), voptCopy.text);
    theApp->style()->drawControl(QStyle::CE_ItemViewItem, &voptCopy, painter, static_cast<QWidget*>(parent()));

    painter->restore();
}

[Gojir4]

@MikhailG Did you tell to your view to use the delegate ? by calling QAbstractItemView::setItemDelegate() or QAbstractItemView::setItemDelegateForColumn() ?

[MikhailG]

@Gojir4 yep! I Did I can see that it draws the ItemView but with a default color.

[Christian Ehrlicher]

@MikhailG said in QItemDelegate impossible to change text color:

I can see that it draws the ItemView but with a default color.

It will also draw when you did not set the delegate... please make sure paint() is really called by e.g. setting a breakpoint or with debug output.

[MikhailG]

@Christian-Ehrlicher yes it stops in paint func under debug

[Gojir4]

@MikhailG I have tested your code and it works well on my side. I have made few modifications but it's globally the same. I have also tested with a custom model to be able to have different color for each row. This is working well. That's strange it's not working on your side.

Here is my code for testing:

void MyItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    painter->save();

    QStyleOptionViewItem itemOpt(option);
    itemOpt.features |= QStyleOptionViewItemV2::HasDisplay;
    itemOpt.text = index.data(Qt::DisplayRole).toString();

    //Color given by model
    itemOpt.palette.setColor(QPalette::Text, index.data(Qt::TextColorRole).value<QColor>());

    //Red only (For QStringListModel)
    //itemOpt.palette.setColor(QPalette::Text, QColor("#FF0000"));

    //painter->drawText(QPoint(voptCopy.rect.x(), voptCopy.rect.y()), voptCopy.text);
    QApplication::style()->drawControl(QStyle::CE_ItemViewItem, &itemOpt, painter);

    painter->restore();
}

My Model used for testing:
coloredstringlistmodel.h

#ifndef MYSTRINGLISTMODEL_H
#define MYSTRINGLISTMODEL_H

#include <QAbstractListModel>
#include <QColor>

struct ColoredString{
    ColoredString(const QString &s, const QColor &c):
        string(s), color(c)
    {}

    QString string;
    QColor color;
};

typedef QList<ColoredString> ColoredStringList;

class MyColoredStringListModel : public QAbstractListModel
{
    Q_OBJECT

public:
    explicit MyColoredStringListModel(QObject *parent = nullptr);

    // Basic functionality:
    int rowCount(const QModelIndex &parent = QModelIndex()) const override;

    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;


    ColoredStringList coloredStringList() const;
    void setColoredStringList(const ColoredStringList &coloredStringList);

private:

    ColoredStringList m_coloredStringList;
};

#endif // MYSTRINGLISTMODEL_H

mystringlistmodel.cpp

#include "mycoloredstringlistmodel.h"

MyColoredStringListModel::MyColoredStringListModel(QObject *parent)
    : QAbstractListModel(parent)
{
}

int MyColoredStringListModel::rowCount(const QModelIndex &parent) const
{
    // For list models only the root node (an invalid parent) should return the list's size. For all
    // other (valid) parents, rowCount() should return 0 so that it does not become a tree model.
    if (parent.isValid())
        return 0;

    return m_coloredStringList.count();
}

QVariant MyColoredStringListModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();


    switch(role){
        case Qt::DisplayRole:
        case Qt::EditRole:
            return m_coloredStringList.at(index.row()).string;

        case Qt::TextColorRole:
            return m_coloredStringList.at(index.row()).color;


    }
    // FIXME: Implement me!
    return QVariant();
}

ColoredStringList MyColoredStringListModel::coloredStringList() const
{
    return m_coloredStringList;
}

void MyColoredStringListModel::setColoredStringList(const ColoredStringList &coloredStringList)
{
    m_coloredStringList = coloredStringList;
}

Usage in a simple widget with a QListView and a QTreeView

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);

    //Test custom model
    ColoredStringList list;
    list << ColoredString("String 1", Qt::red);
    list << ColoredString("String 2", Qt::green);
    list << ColoredString("String 3", Qt::blue);
    list << ColoredString("String 4", Qt::cyan);
    list << ColoredString("String 5", Qt::magenta);
    list << ColoredString("String 6", Qt::yellow);
    m_coloredModel.setColoredStringList(list);

    //Test QStringListModel
    //m_model.setStringList(QStringList() << "Data 1" << "Data 2" << "Data 3" << "Data 4" << "Data 5" << "Data 6" << "Data 7" << "Data 8");

    ui->listView->setItemDelegate(new MyItemDelegate(ui->listView));
    ui->treeView->setItemDelegateForColumn(0, new MyItemDelegate(ui->treeView));

    /*
    ui->listView->setModel(&m_model);
    ui->treeView->setModel(&m_model);
    /*/
    ui->listView->setModel(&m_coloredModel);
    ui->treeView->setModel(&m_coloredModel);
    //*/
}

[MikhailG]

@Gojir4 thanks bro but I got the solution

[Gojir4]

@MikhailG Nice, thanks for sharing your solution