problem with Hebrew font in a control

[HeX0R]

it is only my first time i am using the Qt framework.
and i am just tried to do a simple ui with a list and button.
when the user press the button something will add to the list.
in English its absolutely working but in Hebrew its doesn't.

i tried verity of code the last one was:

void MainWindow::on_pushButton_clicked()
{
ui->listWidget->addItem(trUtf8("שלום"));}

void MainWindow::on_pushButton_clicked()
{
ui->listWidget->addItem(trUtf8("שלום"));}

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edit:
i even tried this code:

QString text = "שלום";
QTextCodec *codec = QTextCodec::codecForName("Windows-1255");
QByteArray encodedString = codec->fromUnicode(text);
ui->textEdit->append(encodedString);

QString text = "שלום";
QTextCodec *codec = QTextCodec::codecForName("Windows-1255");
QByteArray encodedString = codec->fromUnicode(text);
ui->textEdit->append(encodedString);

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Thank you for helping me!