Blocking signal one time in Qt doesn't work correctly

[arkadiusz97]

Hi i have following code:

void MainWindow::on_listWidgetNotes_currentItemChanged(QListWidgetItem *current, QListWidgetItem *previous)//Test!
{
    if(current != NULL)
    {
        ui->plainTextEditContent->setEnabled(true);
        change = false;
        if(isModified)
        {
            auto reply = QMessageBox::question(this, "Test", "Do you want save changes?", QMessageBox::Yes|QMessageBox::No|QMessageBox::Cancel);
            if (reply == QMessageBox::Yes) on_pushButtonSave_clicked();
            else if(reply == QMessageBox::No) notes.closeFile();
            else
            {
                //ui->listWidgetNotes->blockSignals(true);
                ui->listWidgetNotes->setCurrentItem(previous);
                //ui->listWidgetNotes->blockSignals(false);
                return;
            }
        }
        isModified = false;
        this->setWindowTitle(current->text()+" - VfNotes 1.0");
        ui->plainTextEditContent->setPlainText(notes.openFile(current->text()));
    }
}

In specified case code have to show message box and set focus on previous item, after select cancel button.

But setCurrentItem calls on_listWidgetNotes_currentItemChanged again with this message box. After use blockSignals focus doesn't come back on previous element. What to do to set focus on previous item after click cancel, that on_listWidgetNotes_currentItemChanged wasn't call again?

[sierdzio]

@arkadiusz97 said in Blocking signal one time in Qt doesn't work correctly:

void MainWindow::on_listWidgetNotes_currentItemChanged(QListWidgetItem *current, QListWidgetItem *previous)

Try disconnecting the currentItemChanged() signal only and then connecting it again.

Or do it more explicitly: add a boolean member, for example bool ignoreItemChange = false;, then in your slot do this:

void MainWindow::on_listWidgetNotes_currentItemChanged(QListWidgetItem *current, QListWidgetItem *previous)
{
  if (ignoreItemChange) {
    ignoreItemChange = false;
    return;
  }

  // [...]
  else
  {
    ignoreItemChange = true;
    ui->listWidgetNotes->setCurrentItem(previous);
    return;
  }
}

[arkadiusz97]

@sierdzio I was trying this:

void MainWindow::on_listWidgetNotes_currentItemChanged(QListWidgetItem *current, QListWidgetItem *previous)//Test!
{
    if(ignoreItemChange)
    {
        ignoreItemChange = false;
        return;
    }
    if(current != NULL)
    {
        ui->plainTextEditContent->setEnabled(true);
        change = false;
        if(isModified)
        {
            auto reply = QMessageBox::question(this, "Test", "Do you want save changes?", QMessageBox::Yes|QMessageBox::No|QMessageBox::Cancel);
            if (reply == QMessageBox::Yes) on_pushButtonSave_clicked();
            else if(reply == QMessageBox::No) notes.closeFile();
            else
            {
                //ui->listWidgetNotes->blockSignals(true);
                ignoreItemChange = true;
                ui->listWidgetNotes->setCurrentItem(previous);
                //ui->listWidgetNotes->blockSignals(false);
                return;
            }
        }
        isModified = false;
        this->setWindowTitle(current->text()+" - VfNotes 1.0");
        ui->plainTextEditContent->setPlainText(notes.openFile(current->text()));
    }
}

But still focus doesn't come back. ignoreItemChange is set in constructor to false. Disconnecting signal doesn't work too.

disconnect(ui->listWidgetNotes, SIGNAL(currentItemChanged(QListWidgetItem*,QListWidgetItem*)), this, SLOT

(on_listWidgetNotes_currentItemChanged(QListWidgetItem*,QListWidgetItem*)));
                ui->listWidgetNotes->setCurrentItem(previous);
                connect(ui->listWidgetNotes, SIGNAL(currentItemChanged(QListWidgetItem*,QListWidgetItem*)), this, SLOT

(on_listWidgetNotes_currentItemChanged(QListWidgetItem*,QListWidgetItem*)));

[mrjj]

Hi
wondering if you just want a
ui->listWidgetNotes->setFocus();
so the listWidgetNotes get focus back after losing it to the QMessageBox

[arkadiusz97]

@mrjj Did you mean it?

       else
        {
            //ui->listWidgetNotes->blockSignals(true);
            //ui->listWidgetNotes->setCurrentItem(previous);
            ui->listWidgetNotes->setFocus();
            //ui->listWidgetNotes->blockSignals(false);
            return;
        }

I was trying this and focus doesn't come back on previous element too. BTW. Here is full code of project with this problem: https://github.com/arkadiusz97/VfNotes

[mrjj]

@arkadiusz97
Hi
Together with
ui->listWidgetNotes->setCurrentItem(previous);
ui->listWidgetNotes->setFocus();

But after reading again, it sounds like the previous are not being selected ?
Current still is ?

[arkadiusz97]

@mrjj Using ui->listWidgetNotes->setFocus(); has no effects. Now, i used it both with ui->listWidgetNotes->setCurrentItem(previous);. I was testing on blocked signals and without blocking signals.

[arkadiusz97]

This solution was helpful: https://4programmers.net/Forum/C_i_C++/302329-qt5_problem_z_jednorazowa_blokada_sygnalu?p=1437140#id1437140

void MainWindow::on_listWidgetNotes_currentItemChanged(QListWidgetItem *current, QListWidgetItem *previous)
{
    ...
    else
    {
        QTimer::singleShot(0, qApp, [this, previous]
        {
            ui->listWidgetNotes->blockSignals(true);
            ui->listWidgetNotes->setCurrentItem(previous);
            ui->listWidgetNotes->blockSignals(false);
        });
        return;
    }
    ...
}