How to open an URL in a QTableView - c++

Question

What is the best way to present a clickable URL in a QTableView (or QTreeView, QListView, etc...)
Given a QStandardItemModel where some of the columns contain text with URLs I'd like them to become clickable and then handle the click by using QDesktopServices::openURL()
I was hoping there would be some easy way to leverage QLabel's textInteraction flags and to cram them into the table. I can't believe there's not an easier way to handle this. I really hope I'm missing something.

Answer 1

You'll need to create a delegate to do the painting. The code should look something like this:
void RenderLinkDelegate::paint(
QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index
) const
{
QString text = index.data(Qt::DisplayRole).toString();
if (text.isEmpty())
return;
painter->save();
// I only wanted it for mouse over, but you'll probably want to remove
// this condition
if (option.state & QStyle::State_MouseOver)
{
QFont font = option.font;
font.setUnderline(true);
painter->setFont(font);
painter->setPen(option.palette.link().color());
}
painter->drawText(option.rect, Qt::AlignLeft | Qt::AlignVCenter, text);
painter->restore();
}

Answer 2

Well, you can use delegates to render rich text in a qtableview with custom delegates reimplementing the paint method such as:
void CHtmlDelegate::paint(QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
QStyleOptionViewItemV4 opt(option);
QLabel *label = new QLabel;
label->setText(index.data().toString());
label->setTextFormat(Qt::RichText);
label->setGeometry(option.rect);
label->setStyleSheet("QLabel { background-color : transparent; }");
painter->translate(option.rect.topLeft());
label->render(painter);
painter->translate(-option.rect.topLeft());
}
However, it will not make hyperlinks clickable.
To do so, you can use the following hack. Reimplement the setModel method of your table/list view and use setIndexWidget.
void MyView::setModel(QAbstractItemModel *m)
{
if (!m)
return;
QTableView::setModel(m);
const int rows = model()->rowCount();
for (int i = 0; i < rows; ++i)
{
QModelIndex idx = model()->index(i, 1);
QLabel *label = new QLabel;
label->setTextFormat(Qt::RichText);
label->setText(model()->data(idx, CTableModel::HtmlRole).toString());
label->setOpenExternalLinks(true);
setIndexWidget(idx, label);
}
}
In the example above, I replace column 1 with qlabels. Note that you need to void the display role in the model to avoid overlapping data.
Anyway, I would be interested in a better solution based on delegates.

Answer 3

Sadly, its not that easy to render a QLabel with setOpenExternalLinks() when using a QTableView (as opposed to using a QTableWidget). There are no magic two lines of code you can call and have the job done.
use a delegate
set the delegate to the column of your table
use QTextDocument combined with setHTML() to render a html link
this means your model needs to provide an HTML fragment containing a href
calculate the geometry of the link and provide event handlers for to intercept the mouse
change the cursor when it is over the link
execute the action when the link is clicked
what a mess :( i want painter->setWidgetToCell()
--
void LabelColumnItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
if( option.state & QStyle::State_Selected )
painter->fillRect( option.rect, option.palette.highlight() );
painter->save();
QTextDocument document; // <---- RichText
document.setTextWidth(option.rect.width());
QVariant value = index.data(Qt::DisplayRole);
if (value.isValid() && !value.isNull())
{
document.setHtml(value.toString()); // <---- make sure model contains html
painter->translate(option.rect.topLeft());
document.drawContents(painter);
}
painter->restore();
}