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

Jackmill

I have a QListWidget with a model with checkboxes on each item. I've enabled ExtendedSelection as the selection mode, but I still can only toggle one checkbox at a time. Is there a simple way to check/uncheck the checkboxes on all rows selected?

I've tried getting the selected rows from the view's selection model in a connection to QListView::clicked, but that doesn't really work and will get out of step with the rows that are actually selected.

Kent-Dorfman

You don't mention the mouse/keyboard sequence you use to attempt multi-select. so, as remedial as it sounds, that is my first question.

Jackmill

In terms of user input, either by clicking and dragging on rows, or using the shift or ctrl key as defined by the selection mode enum, and then clicking on the checkbox on any of the selected rows. I haven't tried programmatically selecting rows.

Christian Ehrlicher

You have to implement such a behavior by yourself. Simply retrieve the selected rows, iterate over them and set the check state you want.

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.