How to color a single row in QTableView

[blackout69]

Hi everybody,
I need to color a QTableView row with a different color than the one set as style.

void MyClass::show(QString filter)
{
  model = new QSqlRelationalTableModel(this);
  model->setTable(QString("mytable"));
  model->setFilter(filter);
  model->setRelation(2, QSqlRelation("customer", "id_customer", "name"));
  model->setHeaderData(3, Qt::Horizontal, tr("Number"));
  model->setHeaderData(4, Qt::Horizontal, tr("Date"));
  model->setHeaderData(5, Qt::Horizontal, tr("Customer"));
  model->setHeaderData(6, Qt::Horizontal, tr("Total"));
  model->select();

  ui->view->setModel(model);
  ui->view->resizeColumnsToContents();
  ui->view->horizontalHeader()->setStretchLastSection(true);
  ui->view->setItemDelegateForColumn(3, new Custom_Num_Delegate(this));  // Center aligned numbers
  ui->view->setItemDelegateForColumn(4, new Custom_Date_Delegate(this));  // Date Format dd/MM/yyyy
  ui->view->setItemDelegateForColumn(5, new Custom_Two_Delegate(this));  //  Total formatted in € 102,25
}

So far everything works. I have all the data visible on the QTableView.
Using my Custom Delegates I get all the required formatting. Numbers, Date and Total.
Using color_row() I wanted to paint only a few red lines.

void MyClass::color_row()
{
  for(int row = 0; row < model->rowCount(); row++)
    {
      QSqlRecord record = model->record(i);

      if (mycheck)
        {
          for(int column = 0; column < model->columnCount(); column++)
            {
              model->setData(model->index(row,column),QColor(Qt::red), Qt::BackgroundRole); // Not Work
            }
        }
    }
}

But it does not work.
Would anyone know how to give me some advice on how I could solve?
Thank you in advance
blackout69

[eyllanesc]

@blackout69 As I suspected: your model only supports role display. A possible solution is that the delegate has the rows that should have the color and then apply it. I have implemented a delegate that should replace all delegates:

#ifndef DELEGATE_H
#define DELEGATE_H

#include <QStyledItemDelegate>
#include <QDateTime>
#include <QVector>

class Delegate : public QStyledItemDelegate
{
public:
    using QStyledItemDelegate::QStyledItemDelegate;
    QVector<int> rows() const
    {
        return m_rows;
    }
    void setRows(const QVector<int> &rows)
    {
        m_rows = rows;
    }
    
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const override{
        QStyledItemDelegate::initStyleOption(option, index);
        QVariant value = index.data();
        if(index.column() == 3){
            option->displayAlignment = Qt::AlignCenter;
        }
        else if(index.column() == 4){
            option->text = option->locale.toString(value.toDateTime(), "dd/MM/yyyy");
        }
        else if(index.column() == 5){
            option->text = option->locale.toString(value.toDouble(), 'f', 2);
            option->displayAlignment = Qt::AlignRight | Qt::AlignVCenter;
        }
        if(m_rows.contains(index.row())){
            option->backgroundBrush = QBrush(QColor("red"));
        }
    }
private:
    QVector<int> m_rows;
};

#endif // DELEGATE_H

Then:

*.h

Delegate *m_delegate = nullptr;

*.cpp

m_delegate = new Delegate;
ui->view->setItemDelegate(m_delegate);

and:

m_delegate->setRows({1, 2});
ui->view->update();

[SGaist]

Hi,

Are you doing custom painting in your delegates ?

[blackout69]

Hi SGaist,
Yes. This one my custom delegates:

class Custom_Two_Delegate : public QItemDelegate
{
  Q_OBJECT

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

Custom_Two_Delegate::Custom_Two_Delegate(QObject *parent) : QItemDelegate(parent)
{

}

void Custom_Two_Delegate::paint(QPainter *painter, const QStyleOptionViewItem & option, const QModelIndex & index) const
{
  double number = index.model()->data(index, Qt::DisplayRole).toDouble();
  QString text = QString("%L1").arg(number,13,'f',2);
  QStyleOptionViewItem myOption = option;
  myOption.displayAlignment = Qt::AlignRight | Qt::AlignVCenter;
  drawDisplay(painter, myOption, myOption.rect, text);
  drawFocus(painter, myOption, myOption.rect);
}

[SGaist]

Then you have to also handle the BackgroundRole as well there. Usually it would be the first thing you paint and then the rest on top of it.

[blackout69]

I tried to create a custom delegate for coloring, but applying the coloring, I lose the formatting.
I understood that if I apply a custom delegate to the columns, if I apply another one to the rows, it overrides the one applied to the columns

class Color_Delegate_Red : public QItemDelegate
{
  Q_OBJECT

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


Color_Delegate_Red::Color_Delegate_Red(QObject *parent) : QItemDelegate(parent)
{

}

void Color_Delegate_Red::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
  drawBackground(painter, option, index);
  QItemDelegate::paint(painter, option, index);
}

void Color_Delegate_Red::drawBackground(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
  Q_UNUSED(index);
  painter->fillRect(option.rect, QBrush(QColor(Qt::red)));
}

      if (mycheck)
              {
                 ......
                ui->view->setItemDelegateForRow(i, new Color_Delegate_Red(this)); // It works but I lose the formatting 
      	      }

[eyllanesc]

@blackout69 You cannot have 2 delegates for the same item, the last one will replace the previous one. A possible solution is not to modify the paint method but initStyleOption and displayText:

class Custom_Two_Delegate: public QStyledItemDelegate
{
public:
    using QStyledItemDelegate::QStyledItemDelegate;
    QString displayText(const QVariant &value, const QLocale &locale) const override{
        return locale.toString(value.toDouble(), 'f', 2);
    }
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const override{       
        QStyledItemDelegate::initStyleOption(option, index);
        option->displayAlignment = Qt::AlignRight | Qt::AlignVCenter;
    }

};

[SGaist]

You should subclass QStyledItemDelegate. That said, you can't stack them on top of each other. Do the background handling in each of your delegates.

[blackout69]

@eyllanesc
Hi eyllanesc
As you write, column formatting works.
But if I apply the coloring, I lose the formatting.

ui->view->setItemDelegateForRow(i, new Color_Delegate_Red(this));

How do you paint the entire line that interests me?

[eyllanesc]

@blackout69 It seems that you have not understood my answer, with my solution you should not change anything of your initial logic(model->setData(model->index(row,column),QColor(Qt::red), Qt::BackgroundRole); ) only change the implementation of the delegate that I proposed. Don't use setItemDelegateForRow!!!

[blackout69]

@eyllanesc
I write:

ui->view->setItemDelegateForColumn(5, new Custom_Two_Delegate(this));

void MyClass::color_row()
{
  for(int row = 0; row < model->rowCount(); row++)
    {
      QSqlRecord record = model->record(i);

      if (mycheck)
        {
          for(int column = 0; column < model->columnCount(); column++)
            {
              model->setData(model->index(row,column),QColor(Qt::red), Qt::BackgroundRole);
            }
        }

    }
}

Formatting works, but the lines I am interested in are not colored.
mycheck is true!

[SGaist]

I must insiste:

@SGaist said in How to color a single row in QTableView:

Do the background handling in each of your delegates.

[blackout69]

@SGaist
I didn't understand how to apply the coloring in the custom delegates. For example on Custom_Two_Delegate which but posted @eyllanesc

[eyllanesc]

@blackout69 mmm, I assumed that the model you use handled role Qt::BackgroundRole but it seems that this is not true.

1. What model do you use?
2. do you want to change the color of all the rows? Or just from a particular row? if it is a particular row then what does it depend on?
3. Is the color fixed or does it also depend on another condition?

[blackout69]

@eyllanesc

1. I use QSqlRelationalTableModel
2. I just want to color a few lines. The coloring depends on the value of a condition. For simplicity I called it mycheck.
3. The color is fixed.

[JoeCFD]

@blackout69
color all items in that row like the following.
item->setData( Qt::BackgroundRole, QVariant( Qt::red ) );
no delegate is needed.

[eyllanesc]

@blackout69 As I suspected: your model only supports role display. A possible solution is that the delegate has the rows that should have the color and then apply it. I have implemented a delegate that should replace all delegates:

#ifndef DELEGATE_H
#define DELEGATE_H

#include <QStyledItemDelegate>
#include <QDateTime>
#include <QVector>

class Delegate : public QStyledItemDelegate
{
public:
    using QStyledItemDelegate::QStyledItemDelegate;
    QVector<int> rows() const
    {
        return m_rows;
    }
    void setRows(const QVector<int> &rows)
    {
        m_rows = rows;
    }
    
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const override{
        QStyledItemDelegate::initStyleOption(option, index);
        QVariant value = index.data();
        if(index.column() == 3){
            option->displayAlignment = Qt::AlignCenter;
        }
        else if(index.column() == 4){
            option->text = option->locale.toString(value.toDateTime(), "dd/MM/yyyy");
        }
        else if(index.column() == 5){
            option->text = option->locale.toString(value.toDouble(), 'f', 2);
            option->displayAlignment = Qt::AlignRight | Qt::AlignVCenter;
        }
        if(m_rows.contains(index.row())){
            option->backgroundBrush = QBrush(QColor("red"));
        }
    }
private:
    QVector<int> m_rows;
};

#endif // DELEGATE_H

Then:

*.h

Delegate *m_delegate = nullptr;

*.cpp

m_delegate = new Delegate;
ui->view->setItemDelegate(m_delegate);

and:

m_delegate->setRows({1, 2});
ui->view->update();

[eyllanesc]

@JoeCFD What kind of object is "item"? Remember that not all models support role Qt::BackgroundRole.

[JoeCFD]

@eyllanesc
Sorry I am using QTableWidget.

Try this one for all items in one row:
bool QAbstractItemModel::setItemData(const QModelIndex &index, const QMap<int, QVariant> &roles);

in case you have issues, check this out.
https://stackoverflow.com/questions/13265992/qabstractitemmodel-setitemdata-returns-false-when-inserting-qtuserrole

[blackout69]

@eyllanesc
OK well. Now works!
Thanks you have been a great help.

For the sake of completeness, I changed the currency formatting to:
In order to correctly write even the thousands in Euro. Example 1.473,56

double value = index.model()->data(index, Qt::DisplayRole).toDouble();
QString currency = QString("%L1").arg(value,13,'f',2);
option->text = currency;
option->displayAlignment = Qt::AlignRight | Qt::AlignVCenter;