QTableWidget hover entire row without hard-coding background color

[linly]

I've got a QTableWidget, and I want the entire row to be highlighted when mouse hovers on an item.
All the solutions I read from other questions hard code the background color in code, which is not what I want.
I'm using Qt stylesheet to set the background color of the hovered item:

QTableWidget::item:hover {
	background-color: #27292b;
}

And I tried to trick the items in a row into hovered state using a delegate:

#include <QStyledItemDelegate>
class RowHoverDelegate: public QStyledItemDelegate
{
    Q_OBJECT
public:
    RowHoverDelegate(QTableWidget *tableWidget, QObject *parent = 0);
    void paint(QPainter *painter, const QStyleOptionViewItem &option,
               const QModelIndex &index) const;
private:
    QTableWidget *m_tableWdt;
};


// in the implementation file:

RowHoverDelegate::RowHoverDelegate(QTableWidget *tableWidget, QObject *parent)
    : QStyledItemDelegate(parent), m_tableWdt(tableWidget)
{}

void RowHoverDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                             const QModelIndex &index) const
{
    if (option.state & QStyle::State_MouseOver)
    {
        QTableWidgetItem *hovItem = m_tableWdt->item(index.row(), index.column());
        if (hovItem)
        {
            int row = hovItem->row();
            int columnCount = m_tableWdt->columnCount();

            for (int col = 0; col < columnCount; ++col)
            {
                QTableWidgetItem *item = m_tableWdt->item(row, col);
                if (item)
                {
                    QModelIndex idx = m_tableWdt->model()->index(row, col);
                    // copy option from the hovered item (opt is in State_MouseOver state)
                    QStyleOptionViewItem opt = option;
                    // update index and rect
                    opt.index = idx;
                    opt.rect = m_tableWdt->visualItemRect(item);
                    QStyledItemDelegate::paint(painter, opt, idx);  // paint the item
                }
            }
            return;
        }
    }
    QStyledItemDelegate::paint(painter, option, index);
}

In the caller:

    m_tableWdt = new QTableWidget();
    // ...
    RowHoverDelegate *delegate = new RowHoverDelegate(m_tableWdt, m_tableWdt);
    m_tableWdt->setItemDelegate(delegate);

This delegate causes the hovered item and items on the left hand side of it change background, the right hand side items remains unchanged, strange. Can anyone explain this ?

[linly]

OK, I solved it. The key is to update the viewport of the QTableWidget as stated here by Steffen

Here is the impoved delegate:

class RowHoverDelegate : public QStyledItemDelegate
{
    Q_OBJECT
public:
    RowHoverDelegate(QTableWidget *tableWidget, QObject *parent = 0);
    void paint(QPainter *painter, const QStyleOptionViewItem &option,
               const QModelIndex &index) const;

protected slots:
    void onItemEntered(QTableWidgetItem *item);

private:
    QTableWidget *m_tableWdt;
    int m_hoveredRow;
};

Implementation:

RowHoverDelegate::RowHoverDelegate(QTableWidget *tableWidget, QObject *parent)
	: QStyledItemDelegate(parent), m_tableWdt(tableWidget), m_hoveredRow(-1)
{
    // mouse tracking have to be true, otherwise itemEntered won't emit
	m_tableWdt->setMouseTracking(true);
	connect(m_tableWdt, SIGNAL(itemEntered(QTableWidgetItem *)), this, SLOT(onItemEntered(QTableWidgetItem *)));
}

void RowHoverDelegate::onItemEntered(QTableWidgetItem *item)
{
	m_hoveredRow = item->row();
	m_tableWdt->viewport()->update();  // force update
}

void RowHoverDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                             const QModelIndex &index) const
{
	QStyleOptionViewItem opt = option;
	if (index.row() == m_hoveredRow)
	{
		opt.state |= QStyle::State_MouseOver;
	}
	QStyledItemDelegate::paint(painter, opt, index);
}

[JoeCFD]

@linly said in QTableWidget hover entire row without hard-coding background color:

class RowHoverDelegate : public QStyledItemDelegate
{
Q_OBJECT
public:
RowHoverDelegate(QTableWidget *tableWidget, QObject *parent = 0);
void paint(QPainter *painter, const QStyleOptionViewItem &option,
const QModelIndex &index) const;

protected slots:
void onItemEntered(QTableWidgetItem *item);

private:
QTableWidget *m_tableWdt;
int m_hoveredRow;
};

class RowHoverDelegate : public QStyledItemDelegate
{
    Q_OBJECT
public:
    RowHoverDelegate(QTableWidget *tableWidget, QObject *parent = 0);
    void paint(QPainter *painter, const QStyleOptionViewItem &option,
               const QModelIndex &index) const override; /* better to have override here  */

protected slots:
    void onItemEntered(QTableWidgetItem *item);

private:
    QTableWidget *m_tableWdt;
    int m_hoveredRow;
};

[JonB]

@JoeCFD said in QTableWidget hover entire row without hard-coding background color:

override; /* override is needed here */

Hi Joe. Are you claiming this fixes anything? Although specifying override is desirable (I always do), it's not compulsory for anything, other than telling you if you've made a mistake.

[JoeCFD]

@JonB Sorry. Not a fix. it is better to have. I changed it.

[JoeCFD]

@JonB this piece of code will not work well when rows are selected. It is better to have a setting in QTableWidget/View:
something like: enableRowHovering( bool value = false ); I will send a request in the developer's mailing list.