QTableWidget still trigger itemChanged event even if signals blocked

[Sabrac]

Hi guys,
As title, i'm facing with the problem that i have blocked all signals of QTableWidget but the setItem function still trigger itemChanged event.

Is there anyway to prevent itemChanged trigger?

I just know one solution is wrap before and after setItem function by blockSignals(true) again.
But its very annoying if my table have too much cell to set.

[Christian Ehrlicher]

Please show how you're using block signals and your connect statement.

[Sabrac]

@Christian-Ehrlicher said in QTableWidget still trigger itemChanged event even if signals blocked:

Please show how you're using block signals and your connect statement.

Hi christ,
i just block signals like normal

table->blockSignals(true);
// ... Some other logics
table->setItem(0, 0, value0);
table->setItem(0, 1, value1);
table->setItem(0, 2, value2);
table->setItem(0, 3, value3);
// ... Some other logics
table->blockSignals(false);

And i using qt designer to create connect (by right click widget and then choose "go to slot..."

[stryga42]

Are there any other threads in your app which could un-block the table object in the meantime?

[Christian Ehrlicher]

Works fine for me (Qt6):

#include <QtWidgets>

int main(int argc, char **argv)
{
  QApplication app(argc, argv);
  bool blockSignals = argc > 1;
  QTableWidget tw;
  tw.show();
  tw.setColumnCount(1);
  tw.setRowCount(1);
  QObject::connect(&tw, &QTableWidget::itemChanged, [&]() { qDebug() << "Item changed!"; });
  QTimer::singleShot(10, &tw, [&]() {
    if (blockSignals)
      tw.blockSignals(true);
    tw.setItem(0,  0, new QTableWidgetItem("Blub"));
    if (blockSignals)
      tw.blockSignals(false);
  });
  return app.exec();
}

[JoeCFD]

@Sabrac
there is a return value from blockSignals(true). Check it out. The return value is the previous value of signalsBlocked().
https://doc.qt.io/qt-5.15/qobject.html#blockSignals

There is another way to avoid any unnecessary changes caused by a specific signal.

disconnect( table, signal, this, slot);
// ... Some other logics
table->setItem(0, 0, value0);
table->setItem(0, 1, value1);
table->setItem(0, 2, value2);
table->setItem(0, 3, value3);
// ... Some other logics
 connect( table, signal, this, slot);

This may work better sometimes since you may not want to block all signals.