QListWidget with checkboxes - checking more than one row at a time

Jackmill

I think the challenge I'm having with that is differentiating between when the user clicks on the checkbox and when the user clicks anywhere in the QListView.

I have tried subclassing QListView and reimplementing mouseReleaseEvent, but it never seems to be called:

class MassCheckView : public QListView {
	Q_OBJECT
	public:
		explicit MassCheckView(QWidget* parent = nullptr) : QListView(parent) {}

		void mouseReleaseEvent(QMouseEvent *event) override;
};

--

void MassCheckView::mouseReleaseEvent(QMouseEvent *event) {
	auto under_mouse = childAt(event->position());
	if (under_mouse) {
		const auto indices = selectionModel()->selectedIndexes();
		const auto first_checked = model()->data(indices.at(0), Qt::CheckStateRole).value<Qt::CheckState>();

		for (const auto& idx : indices) {
			model()->setData(model()->index(idx.row(), idx.column(), QModelIndex()),
				first_checked ? Qt::Unchecked : Qt::Checked,
				Qt::CheckStateRole);
		}

		return;
	}

	QListView::mouseReleaseEvent(event);
}

Christian Ehrlicher

Now you're using a QListView instead a QListWidget... you have to monitor your model to see when the checkstate changed then.

Jackmill

Oh shoot; that's my mistake -- I've meant QListView for this whole post.

How might I go about that? I can connect something to dataChanged, but as far as I'm aware it will still only change one index at a time regardless of how many rows are selected.

Christian Ehrlicher

@Jackmill said in QListWidget with checkboxes - checking more than one row at a time:

far as I'm aware it will still only change one index at a time regardless of how many rows are selected.

Yes, you get the dataChanged() signal, then lookup the selection and set the rest.

Jackmill

I see. This seems to work:

connect(model, &QAbstractListModel::dataChanged,
		this, [table, model](const QModelIndex& topLeft, const QModelIndex& bottomRight) {
			const auto selection = table->selectionModel()->selectedIndexes();

			if (selection.isEmpty()) { return; }

			const auto check = model->data(topLeft, Qt::CheckStateRole).value<Qt::CheckState>();

			model->setDataChangedEnabled(false);
			for (const auto& idx : selection) {
				if (!idx.isValid() || idx == topLeft) { continue; }

				model->setData(idx, check ? Qt::Checked : Qt::Unchecked, Qt::CheckStateRole);
			}
			model->setDataChangedEnabled(true);
		});

Enabling and disabling the emission of the dataChanged like this seems a little clunky but without it there's an endless loop and segfault.

jeremy_k

@Jackmill said in QListWidget with checkboxes - checking more than one row at a time:

Enabling and disabling the emission of the dataChanged like this seems a little clunky but without it there's an endless loop and segfault.

Blocking the dataChanged signal means that the view won't know that a particular cell needs to be redrawn. A flag or list of indexes to be modified could accomplish the same goal while leaving view management intact.

Christian Ehrlicher

@Jackmill said in QListWidget with checkboxes - checking more than one row at a time:

check ? Qt::Checked

And this is wrong - see https://doc.qt.io/qt-6/qt.html#CheckState-enum
simply pass check

Also notice that you have to map the indexes as soon as you have a proxy model in between.

Jackmill

@jeremy_k said in QListWidget with checkboxes - checking more than one row at a time:

A flag or list of indexes to be modified could accomplish the same goal while leaving view management intact.

How might I do this? I'm having trouble thinking of a way to call setData without causing an endless loop.

Christian Ehrlicher

Just remeber which you already have set and that you're currently setting the other checkboxes.

jeremy_k

@Jackmill said in QListWidget with checkboxes - checking more than one row at a time:

@jeremy_k said in QListWidget with checkboxes - checking more than one row at a time:

A flag or list of indexes to be modified could accomplish the same goal while leaving view management intact.

How might I do this? I'm having trouble thinking of a way to call setData without causing an endless loop.

void onDataChanged(const QModelIndex topLeft, const QModelIndex bottomRight, const QList<int> &roles)
{
    static bool updating = false;
    if (roles.contains(ItemDataRole::CheckStateRole) && !updating) {
        updating = true;
        auto value = topLeft.data(ItemDataRole::CheckStateRole);
        for (auto index : selectionModel.selectedIndexes())
            model->setData(index, ItemDataRole::CheckStateRole, value);
        updating = false;
    }
}

The code could also disconnect this (and only this) slot from the signal prior to the loop, and reconnect it at the end.