Set color to tableview to certain row

[Thank You]

Here I want to show row "GREEN" to row with important false
and "BLUE" to row with important true

It is fetched from database using mysql query

    tb= QSqlDatabase::addDatabase("QMYSQL","full-settings-table");
    tb.setDatabaseName("message");
    tb.setPort(3306);
    tb.setHostName("localhost");
    tb.setUserName("root");
    tb.setPassword("");
  QString command = "select * from messages;";
    {

  
    if(tb.open()){
        QSqlQueryModel *model = new QSqlQueryModel();
           QSqlQuery *query = new QSqlQuery(tb);
           query->prepare(command);
        if(query->exec()){
            model->setQuery(*query);

            ui->data->setModel(model);

        }else{
 //   QMessageBox::warning(this,"dataaaaaaa","not\n"+query->lastError().text());
        }

    }else{
//not connected
    }

    }
        QSqlDatabase::removeDatabase("report"); // removing database

I have gone through these
https://forum.qt.io/topic/83984/how-to-set-current-cell-color-in-a-tableview-and-how-to-set-text-centeraligned
https://forum.qt.io/topic/125874/qtableview-set-background-color-to-some-columns/3

They all say some kind of different things Like proxy model and delegate.
But I don't know about this topic.

So is there simple way to implement this?

[VRonin]

I am really torn, here there are 2 solutions:
1)

class BackgroundBrushDelegate : public QStyledItemDelegate{
    Q_OBJECT
    Q_DISABLE_COPY(BackgroundBrushDelegate)
public:
    explicit BackgroundBrushDelegate(QObject *parent = nullptr)
        : QStyledItemDelegate(parent)
    {}
    BackgroundBrushDelegate(const QBrush& brush, QObject *parent = nullptr)
        : QStyledItemDelegate(parent)
    {}
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const override
    {
        QStyledItemDelegate::initStyleOption(option,index);
        if(index.siblingAtColumn(3).data().toBool())
            option->backgroundBrush = QBrush(Qt::blue);
        else
            option->backgroundBrush = QBrush(Qt::green);
    }
};

ui->data->setItemDelegate(new BackgroundBrushDelegate(this));

---

class BackgroundBrushProxy : public QIdentityProxyModel{
    Q_OBJECT
    Q_DISABLE_COPY(BackgroundBrushProxy)
public:
    explicit BackgroundBrushProxy(QObject *parent = nullptr)
        : QIdentityProxyModel(parent)
    {}
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override{
        if(role == Qt::BackgroundRole && index.isValid()){
            if(index.siblingAtColumn(3).data().toBool())
                return QBrush(Qt::blue);
            return QBrush(Qt::green)
        }
        return QIdentityProxyModel::data(index,role);
    }
};

And replace ui->data->setModel(model); with:

BackgroundBrushProxy *proxy = new BackgroundBrushProxy(this);
proxy->setSourceModel(model);
ui->data->setModel(proxy);

The decision on which is better, however, is purely philosophical (is it just user representation so use 1 or is a property of the data and 2 should be used?) and both work. The argument to siblingAtColumn is what determines what column is looked at, you probably want to handle it with a private variable + getter/setter methods or with an enum in real code to avoid it breaking when you change the code later on

---

P.S.
In your code example you are likely leaking the model and there is no reason to allocate the query on the heap. It should be:

 if(tb.open()){
        QSqlQueryModel *model = new QSqlQueryModel(this);
           QSqlQuery query(tb);
           query.prepare(command);
        if(query.exec()){
            model->setQuery(query);

            ui->data->setModel(model);

[SGaist]

Hi,

Implement a custom QIdentityProxyModel and return the color you want for the background role of that column based on the value at the index.

[Thank You]

@SGaist
I was about to ask this question. I prepared whole question but was still searching for the answer.
I found this one written by @VRonin (Thank you sir)

class BackgroundBrushDelegate : public QStyledItemDelegate{
    Q_OBJECT
    Q_PROPERTY(QBrush backgroundBrush READ backgroundBrush WRITE setBackgroundBrush NOTIFY backgroundBrushChanged)
    Q_DISABLE_COPY(BackgroundBrushDelegate)
public:
    explicit BackgroundBrushDelegate(QObject *parent = nullptr)
        : QStyledItemDelegate(parent)
    {}
    BackgroundBrushDelegate(const QBrush& brush, QObject *parent = nullptr)
        : QStyledItemDelegate(parent)
        , m_backgroundBrush(brush)
    {}
    const QBrush& backgroundBrush() const { return m_backgroundBrush; }
    void setBackgroundBrush(const QBrush& brush)
    {
        if(m_backgroundBrush==brush)
            return;
        m_backgroundBrush=brush;
        backgroundBrushChanged(m_backgroundBrush);
    }
signals:
    void backgroundBrushChanged(const QBrush& brush);
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const override
    {
        QStyledItemDelegate::initStyleOption(option,index);
        option->backgroundBrush = m_backgroundBrush;
    }
private:
    QBrush m_backgroundBrush;
}

I am using it. But I don't know how it works and other stuffs.

In addition to @mrjj, QIdentityProxyModel is also a solution.

In that question also You mentioned it but I don't know both of these.

After searching about this, I found majority of answers include either https://doc.qt.io/qt-5/qidentityproxymodel.html or Delegate.

I would be happy to get the answer which looks simple. I am not pro at it. I understand the syntax of upper code but I can't visualize it( I don't know what delegate is and what ProxyModel is 😂😂, I just know sth about model ).

Thank You 😊☺

[JoeCFD]

Assign background color to each item of that row.

[SGaist]

Did you already went through the Model View introduction in Qt's documentation ?

[Thank You]

@SGaist I knew something about this before.
I will read it now
Thanks

[VRonin]

I am really torn, here there are 2 solutions:
1)

class BackgroundBrushDelegate : public QStyledItemDelegate{
    Q_OBJECT
    Q_DISABLE_COPY(BackgroundBrushDelegate)
public:
    explicit BackgroundBrushDelegate(QObject *parent = nullptr)
        : QStyledItemDelegate(parent)
    {}
    BackgroundBrushDelegate(const QBrush& brush, QObject *parent = nullptr)
        : QStyledItemDelegate(parent)
    {}
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const override
    {
        QStyledItemDelegate::initStyleOption(option,index);
        if(index.siblingAtColumn(3).data().toBool())
            option->backgroundBrush = QBrush(Qt::blue);
        else
            option->backgroundBrush = QBrush(Qt::green);
    }
};

ui->data->setItemDelegate(new BackgroundBrushDelegate(this));

---

class BackgroundBrushProxy : public QIdentityProxyModel{
    Q_OBJECT
    Q_DISABLE_COPY(BackgroundBrushProxy)
public:
    explicit BackgroundBrushProxy(QObject *parent = nullptr)
        : QIdentityProxyModel(parent)
    {}
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override{
        if(role == Qt::BackgroundRole && index.isValid()){
            if(index.siblingAtColumn(3).data().toBool())
                return QBrush(Qt::blue);
            return QBrush(Qt::green)
        }
        return QIdentityProxyModel::data(index,role);
    }
};

And replace ui->data->setModel(model); with:

BackgroundBrushProxy *proxy = new BackgroundBrushProxy(this);
proxy->setSourceModel(model);
ui->data->setModel(proxy);

The decision on which is better, however, is purely philosophical (is it just user representation so use 1 or is a property of the data and 2 should be used?) and both work. The argument to siblingAtColumn is what determines what column is looked at, you probably want to handle it with a private variable + getter/setter methods or with an enum in real code to avoid it breaking when you change the code later on

---

P.S.
In your code example you are likely leaking the model and there is no reason to allocate the query on the heap. It should be:

 if(tb.open()){
        QSqlQueryModel *model = new QSqlQueryModel(this);
           QSqlQuery query(tb);
           query.prepare(command);
        if(query.exec()){
            model->setQuery(query);

            ui->data->setModel(model);