Size of icon display in QTableView

[Perdrix]

I think I may need a QStyledItemDelegate subclass, a bit like:

class IconSizeDelegate : public QStyledItemDelegate
{
Q_OBJECT

public:
	using QStyledItemDelegate::QStyledItemDelegate;


protected:
	void paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const override;
	inline QSize sizeHint(const QStyleOptionViewItem& option, const QModelIndex& index) const
	{
		QSize result = QStyledItemDelegate::sizeHint(option, index);
		result.setHeight(result.height() * 1.2);
		return result;
	}

};

The question then is what goes in the paint mf if I want to increase the iconsize for any cells that have a QIcon associated with them (in this case it's all cells in column 0 and that has a selection check box, and Icon and text).

I know it's not as simple as:

void IconSizeDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
	{
		if (index.data().canConvert<QIcon> ())
		{
			QIcon icon = qvariant_cast<QIcon> (index.model()->data(index, Qt::DecorationRole));
			//scale it . note must be big enough or you get a smaller
			QSize iconSize = option.decorationSize;
			iconSize *= 2;
			QPixmap iconPixmap = icon.pixmap(iconSize);
			//draw icon
			painter->drawPixmap(option.rect.x(), option.rect.center().y() - mysize.height() / 2, iconPixmap);
		}
	}

and then:

IconSizeDelegate* iconSizeDelegate{ new IconSizeDelegate() };
ui->tableView->setItemDelegateForColumn(0, iconSizeDelegate);

Because that didn't work (the column wasn't rendered at all - cells were blank).

So what should it contain?

[Perdrix]

Here's what it looked like before:

I've had another attempt at the IconSizeDelegate which doesn't quite work (no check box, text formatted without ellipsis :( )

Here's the code that produced the above result:

void IconSizeDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
	Q_ASSERT(index.isValid());
	QStyleOptionViewItem opt{ option };
	initStyleOption(&opt, index);

	QStyle* style = opt.widget ? opt.widget->style() : QApplication::style();
	QRect rect = opt.rect;

	constexpr uint neededFeatures
	{ static_cast<uint>(QStyleOptionViewItem::HasCheckIndicator |
		QStyleOptionViewItem::HasDisplay |
		QStyleOptionViewItem::HasDecoration) };

	Q_ASSERT(neededFeatures == (opt.features & neededFeatures));
		
	Qt::CheckState state = opt.checkState;
	QIcon icon = qvariant_cast<QIcon> (index.model()->data(index, Qt::DecorationRole)); 
	QString text = index.model()->data(index, Qt::DisplayRole).toString();

	painter->save();
	
	//
	// Draw the check box normally
	//
	QStyleOptionButton checkBoxStyle;
	checkBoxStyle.state = (Qt::Checked == state) ? QStyle::State_On : QStyle::State_Off;
	style->drawPrimitive(QStyle::PE_IndicatorCheckBox, &checkBoxStyle, painter);
	//
        // Draw the icon twice as large as the default
	//
	QRect nextRect{ rect };
	nextRect.setLeft(nextRect.left() + checkBoxStyle.rect.width());
	QSize iconSize = opt.decorationSize;
	iconSize.scale(2 * iconSize.width(), 2 * iconSize.height(), Qt::KeepAspectRatio);
	QPixmap iconPixmap{ icon.pixmap(iconSize) };
	painter->drawPixmap(nextRect.x(), nextRect.center().y() - iconSize.height() / 2, iconPixmap);

	//
	// Draw the text as normal
	//
	nextRect.setLeft(nextRect.left() + iconSize.width());
	if (option.features & QStyleOptionViewItem::WrapText)
		painter->drawText(nextRect, Qt::AlignLeft | Qt::AlignTop | Qt::TextWordWrap, text);
	else
		painter->drawText(nextRect, Qt::AlignLeft | Qt::AlignVCenter, text);
	painter->restore();
}

What have I missed or got wrong? Should I instead have changed option.decorationSize and invoked the base class paint mf? Can the decoration size be over-ridden using a style sheet? There seems to be a sub-element style for this: QStyle::SE_ItemViewItemDecoration

Thanks
David

[Perdrix]

Any clues? Thanks David

[mpergand]

@Perdrix said in Size of icon display in QTableView:

Any clues? Thanks David

No cos your code is over convoluted ...

To return to the beginning, drawing an icon with a specific size in a table column, I'm simply doing this:

case Qt::DecorationRole:
    if(index.column()==Check) return Icon->pixmap(Icon->actualSize(QSize(rowHeight-5,rowHeight-5)));
    break;

rowHeight is the value return by table->verticalHeader()->defaultSectionSize();

[Perdrix]

I'm using a sub-classed QStyledItemDelegate because that's what the documentation says I need to do.

Where is your code: in the data() mf??

[mpergand]

@Perdrix

Here the complete source:

// resizing icon in tableView cell
#define Check 0
#define Text 1
int rowHeight;
QIcon* Icon;


struct Model : public QAbstractTableModel
{

explicit	Model() : QAbstractTableModel(nullptr) {}

        int	rowCount(const QModelIndex &/*parent*/) const
            {
            return 8;
            }

        int	columnCount(const QModelIndex &/*parent*/) const
            {
            return 2;
            }

    QVariant data(const QModelIndex &index, int role=Qt::DisplayRole) const
            {
            if(!index.isValid()) return QVariant();
            int row=index.row();

            switch (role)
                {
                case Qt::DisplayRole:
                    if(index.column()==Text) return QString("row %1 Col %2").arg(index.row()).arg(index.column());
                    if(index.column()==Check) return QString("Check box");
                    break;

                case Qt::CheckStateRole:
                    if(index.column()==Check) return row%3;
                    break;

                case Qt::DecorationRole:
                    if(index.column()==Check) return Icon->pixmap(Icon->actualSize(QSize(rowHeight-5,rowHeight-5)));
                    break;
                }

            return QVariant();
            }

    Qt::ItemFlags flags(const QModelIndex &index) const
            {Q_UNUSED(index)
            Qt::ItemFlags f=Qt::ItemIsSelectable|Qt::ItemIsEnabled;

            if(index.column()==Check)
                f|=Qt::ItemIsUserCheckable;

            return f;
    }
};

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

    QString path=QDir::homePath()+"/Desktop/Developpement/Qt5.12/Divers/Essai/img/ic32.jpg";
    Icon=new QIcon(path);
    qDebug()<<QFile::exists(path)<<path;

    auto table=new QTableView;
    table->setModel(new Model);
    rowHeight=table->verticalHeader()->defaultSectionSize();
    table->horizontalHeader()->setMinimumSectionSize(150);
    table->resize(400,400);
    table->show();

return app.exec();

[Perdrix]

I can see how that works. I would still like to know how one is supposed to do it with a sub-classed QStyledItemDelegate as that is how you're supposed to do it.

[mpergand]

class ItemDelegate : public QStyledItemDelegate
{
        void    paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
        {
            QRect rec=option.rect;
            QSize source=Icon->actualSize(rec.size());

             QPixmap pixmap=Icon->pixmap(Icon->actualSize(QSize(rowHeight-5,rowHeight-5)));
             QRect target=QRect(rec.topLeft(),source);
             target.translate(2,2);
             painter->drawPixmap(target, pixmap, QRect(QPoint(0,0),source));
        }
};

Added to a third column:
table->setItemDelegateForColumn(2,new ItemDelegate);

[Perdrix]

Hmmphh... I'm quite sure from the other examples I've seen that what you've shown me isn't the "proper way to do it".

I got the checkbox display working by changing the checkbox display code:

		//
		// Draw the check box normally
		//
		QStyleOptionButton checkBoxStyle;
		constexpr int size = 17;
		constexpr int space = 6;
		checkBoxStyle.rect = QRect(opt.rect.x(),
			opt.rect.center().y() - (size / 2),
			size,
			size);
		
		checkBoxStyle.state = (Qt::Checked == state) ? QStyle::State_On : QStyle::State_Off;
		style->drawPrimitive(QStyle::PE_IndicatorItemViewItemCheck, &checkBoxStyle, painter);

		//
		// Draw the icon twice as large as the default
		//
		QRect nextRect{ rect };
		nextRect.setLeft(nextRect.left() + checkBoxStyle.rect.width() + space);

Which I admit is not ideal as it uses hard coded values for the size of the checkbox and the spacing. Surely there's a way to find the default size of a Primitive Element such as a PE_IndicatorItemViewItemCheck???

I also still want to know how to get the ellipsis handling for the text done.

[mpergand]

For elided text see;
QString QFontMetrics::elidedText(const QString &text, Qt::TextElideMode mode, int width, int flags = 0)

Quick test to get the size of a checkbox:

QStyle *style = QApplication::style();
              QRect r=style->subElementRect(QStyle::SE_ItemViewItemCheckIndicator, &opt);
              qDebug()<<r.size(); // 19x18 for OSX

see here for more infos:
https://wiki.qt.io/Center_a_QCheckBox_or_Decoration_in_an_Itemview

[Perdrix]

Thank you, that helps enormously!!!