Skeleton to switch a QMainWindow's palette, as well as all the child widgets' palette (can be used for dynamic theming)

mainwindow.cpp

// The button clicked events can be replaced with any slots, and/or you can define the 
// switchPalette() to be a slot to use with QObject::connect()

// Dark Palette push button
void MainWindow::on_switchToDarkTheme_clicked()
{
    this->switchPalette(darkPalette);
}

// Light palette push button
void MainWindow::on_switchToLightTheme_clicked()
{
    this->switchPalette(lightPalette);
}

void MainWindow::switchPalette(const QPalette& palette)
{
    this->setPalette(palette);

    QList<QWidget*> widgets = this->findChildren<QWidget*>();

    foreach (QWidget* w, widgets)
    {
        w->setPalette(palette);
    }
}