There is a showNormal() between showFullScreen() and showMaximized()?

sonichy

There is a showNormal() between showFullScreen() and showMaximized()?
When I switch between showFullScreen() and showMaximized(), I can see the window turn to showNormal(), and I can see the desktop.
Another problem: QTabWidget has 1px border, how to set to none border?
alt text
source code: https://github.com/sonichy/Qt_HTYBrowser

void MainWindow::fullScreen()
{
    if(isFullScreen()){
        showMaximized();
        ui->statusBar->show();
        ui->navbar->show();
        ui->tabWidget->tabBar()->show();
        ui->progressBar->show();
    }else{
        showFullScreen();
        ui->statusBar->hide();
        ui->navbar->hide();
        ui->tabWidget->tabBar()->hide();
        ui->progressBar->hide();
        find_dialog->hide();
    }
}