selectionChanged() not called when item selected with setCurrentIndex() is deselected

[EaccB]

I move through a QListView with Previous and Next buttons. I do this with setCurrentIndex(), using the currently selected index +/-1, and QItemSelectionModel::SelectCurrent.

However, if the item is deselected with CTRL+click, selectionChanged() is not emitted as it is if I had clicked on the item and then deselected. So, how can I select an item in the list such that it is the same as if I had clicked on it?

[SGaist]

Hi,

So you move the selection with your button and then "unselect" it with the mouse and this does not trigger the signal ?

[EaccB]

@SGaist

That is correct.
If I select the item by clicking on it and then deselecting, it works fine.

The index to select the next item is calculated: index(selection.indexes().at(0).row() + 1, 0)

[SGaist]

Which version of Qt are you using ?

Can you provide a minimal compilable example that shows this behaviour ?

[EaccB]

Using Qt_5_13_1. I'm using a custom model and delegate and QSortFilterProxyModel.
Just tried reproducing using QStringListModel and it woks fine. Not really sure where I should be looking.

[EaccB]

I notice that using the keyboard arrow keys works, so I could replicate the way in which they make a selection, if you know how that's done? Also important to point out that deselecting the item does "un-highlight" it, so clearly the deselection is being registered somewhere.

[EaccB]

@SGaist,

I've written a test application which demonstrates this behaviour. How/where can I host this? Looks like the forum doesn't allow attachments.

[Christian Ehrlicher]

Create a bug report, attach the testcase.
But since the example should not be longer than 50 lines (at least I would expect this from your description) and doesn't need a ui file you can also paste it here (don't forget the code tags!)

[EaccB]

@SGaist @Christian-Ehrlicher ,

The problem appears to be related to the use of QSortFilterProxyModel. The following example uses QStringListModel and QSortFilterProxyModel for sorting in ascending order:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QStringList>
#include <QStringListModel>
#include <QAbstractItemView>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

    void newSelection(const QItemSelection &selected, const QItemSelection &deselected);

private slots:
    void on_add_clicked();

    void on_insert_clicked();

    void on_delete_2_clicked();



    void on_selectItem2_clicked();

private:
    Ui::MainWindow *ui;
    QStringListModel *model;
};
#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QSortFilterProxyModel>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    // Create model
        model = new QStringListModel(this);

        // Make data
        QStringList List;
        List << "Clair de Lune" << "Reverie" << "Prelude";

        // Populate our model
        model->setStringList(List);

        // Glue model and view together
        ui->listView->setModel(model);
        ui->comboBox->setModel(model);
        QSortFilterProxyModel* proxy = new QSortFilterProxyModel();
        proxy->setSourceModel(model);
        proxy->setSortRole(Qt::DisplayRole);
        proxy->setDynamicSortFilter(true);
        ui->listView->setModel(proxy);
        proxy->sort(0);

        // Add additional feature so that
        // we can manually modify the data in ListView
        // It may be triggered by hitting any key or double-click etc.
        ui->listView->
                setEditTriggers(QAbstractItemView::AnyKeyPressed |
                                QAbstractItemView::DoubleClicked);
        QItemSelectionModel* selectionModel = ui->listView->selectionModel();
        connect(selectionModel, &QItemSelectionModel::selectionChanged, this, &MainWindow::newSelection);
}

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_add_clicked()
{
    // Add button clicked
        // Adding at the end

        // Get the position
        int row = model->rowCount();

        // Enable add one or more rows
        model->insertRows(row,1);

        // Get the row for Edit mode
        QModelIndex index = model->index(row);

        // Enable item selection and put it edit mode
        ui->listView->setCurrentIndex(index);
        ui->listView->edit(index);
}

void MainWindow::on_insert_clicked()
{
    // Insert button clicked

        // Get the position
        int row = ui->listView->currentIndex().row();

        // Enable add one or more rows
        model->insertRows(row,1);

        // Get row for Edit mode
        QModelIndex index = model->index(row);

        // Enable item selection and put it edit mode
        ui->listView->setCurrentIndex(index);
        ui->listView->edit(index);
}

void MainWindow::on_delete_2_clicked()
{
    // Delete button clicked
        // For delete operation,
        // we're dealing with a Model not a View
        // Get the position
        model->removeRows(ui->listView->currentIndex().row(),1);
}

void MainWindow::newSelection(const QItemSelection &selected, const QItemSelection &deselected){

    int x = 5; //Enter new Selection
}

void MainWindow::on_selectItem2_clicked()
{
    QItemSelection selection = ui->listView->selectionModel()->selection();
    QModelIndex index = model->index(1, 0);
    ui->listView->selectionModel()->clearSelection();
    ui->listView->selectionModel()->setCurrentIndex(index, QItemSelectionModel::ClearAndSelect);
}

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>661</width>
    <height>360</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QWidget" name="">
    <property name="geometry">
     <rect>
      <x>90</x>
      <y>20</y>
      <width>258</width>
      <height>251</height>
     </rect>
    </property>
    <layout class="QGridLayout" name="gridLayout_2">
     <item row="0" column="0">
      <widget class="QListView" name="listView"/>
     </item>
     <item row="1" column="0">
      <layout class="QGridLayout" name="gridLayout">
       <item row="0" column="2">
        <widget class="QPushButton" name="delete_2">
         <property name="text">
          <string>Delete</string>
         </property>
        </widget>
       </item>
       <item row="2" column="0" colspan="3">
        <widget class="QComboBox" name="comboBox"/>
       </item>
       <item row="0" column="1">
        <widget class="QPushButton" name="insert">
         <property name="text">
          <string>Insert</string>
         </property>
        </widget>
       </item>
       <item row="0" column="0">
        <widget class="QPushButton" name="add">
         <property name="text">
          <string>Add</string>
         </property>
        </widget>
       </item>
       <item row="1" column="0" colspan="3">
        <widget class="QPushButton" name="selectItem2">
         <property name="text">
          <string>Select Item 2</string>
         </property>
        </widget>
       </item>
      </layout>
     </item>
    </layout>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>661</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

To test, set a breakpoint in the newSelection() slot. Run in debug mode and press "Select Item 2". Notice then, that when you "unselect" with CTRL+Click, the slot is not entered (presumably the selectionChanged() signal is not emitted).

[EaccB]

Can someone please confirm if this is a Qt bug before I file a bug report?

[Christian Ehrlicher]

Here are readable minimal example which is working:

#include <QtWidgets>

class MainWindow : public QWidget
{
public:
  MainWindow(QWidget *parent = nullptr);
  void newSelection(const QItemSelection &selected, const QItemSelection &deselected);
  void onSelectItem();
  QListView *lv;
};

MainWindow::MainWindow(QWidget *parent)
  : QWidget(parent)
{
  QVBoxLayout *lay = new QVBoxLayout(this);
  lv = new QListView(this);
  lay->addWidget(lv);
  auto pb = new QPushButton("Select item 2");
  lay->addWidget(pb);

  auto model = new QStringListModel({"Clair de Lune", "Reverie", "Prelude"}, this);
  auto proxy = new QSortFilterProxyModel(this);
  proxy->setSortRole(Qt::DisplayRole);
  proxy->setDynamicSortFilter(true);
  proxy->setSourceModel(model);
  proxy->sort(0);
  lv->setModel(proxy);

  // Add additional feature so that
  // we can manually modify the data in ListView
  // It may be triggered by hitting any key or double-click etc.
  lv->setEditTriggers(QAbstractItemView::AnyKeyPressed |
                      QAbstractItemView::DoubleClicked);
  QItemSelectionModel* selectionModel = lv->selectionModel();
  connect(selectionModel, &QItemSelectionModel::selectionChanged, this, &MainWindow::newSelection);

  connect(pb, &QPushButton::clicked, this, &MainWindow::onSelectItem);
}

void MainWindow::newSelection(const QItemSelection &selected, const QItemSelection &deselected)
{
  qDebug() << "selectionChanged, selected:" << selected << ", deselected:" << deselected;
}

void MainWindow::onSelectItem()
{
  QItemSelection selection = lv->selectionModel()->selection();
  QModelIndex index = lv->model()->index(1, 0);
  lv->selectionModel()->clearSelection();
  lv->selectionModel()->setCurrentIndex(index, QItemSelectionModel::ClearAndSelect);
}

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

  MainWindow mw;
  mw.show();
  return app.exec();
}

You use the wrong model in your MainWindow::on_selectItem2_clicked() slot.