Unexpected behavior on QWidget while the event filtering

Question

Just i've tested the following codes on QPushButton and on QWidget and i've encountered with different behaviors. But why?

MainWindow::MainWindow(QWidget *parent) 
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->widget->setStyleSheet("background:blue;");
    ui->pushButton->setStyleSheet("background:blue;");
    ui->widget->installEventFilter(this);
    ui->pushButton->installEventFilter(this);

        ...
}

bool MainWindow::eventFilter(QObject* watched, QEvent* event)
{
    if (watched==ui->pushButton && event->type()==QEvent::Paint)
    {
        // Do nothing
        return true;
    }
    else if (watched==ui->widget && event->type()==QEvent::Paint)
    {
        // Do nothing
        return true;
    }
    else
        return QMainWindow::eventFilter(watched, event);
}

Then, the pushButton has disappeared as normally, because i've masked its paintEvent with eventFilter. But the widget has painted to blue. Why widget hasn't disappeared.

Answer 1

I've solved the problem with changing QEvent::Paint with QEvent::Polish.

To who wanted the detailed description

Thanks everybody.