QTreeWidget setCurrentItem difference height with the same setStyleSheet

[trytoremeber963]

case 0:
if i do not use any setCurrentItem function in the QTreeWidget,all the item are normal

QApplication a(argc, argv);  
 
    QString str1;
    str1.append("uistyle.css");
    QFile file(str1);
 
    if(file.open(QFile::ReadOnly))
    {
        QString styleSheet = QObject::tr(file.readAll());
        a.setStyleSheet(styleSheet);
        file.close();
    }
 
    MainWindow w;  
    w.show();
    return a.exec();

QApplication a(argc, argv);  
    
    QString str1;
    str1.append("uistyle.css");
    QFile file(str1);

    if(file.open(QFile::ReadOnly))
    {
        QString styleSheet = QObject::tr(file.readAll());
        a.setStyleSheet(styleSheet);
        file.close();
    }

    MainWindow w;  
    w.show();
    return a.exec();

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ui->setupUi(this);
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(0));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(1));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(2));

ui->setupUi(this);
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(0));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(1));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(2));

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case 1:

in the main function i have used the setStyleSheet and use it before the mainwindow's construct function

if i use

ui->setupUi(this);
    ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(0));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(1));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(2));

ui->setupUi(this);
    ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(0));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(1));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(2));

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the first and the last item height are UNNormal but the second and the third is NORMAL
all the sub items are normal

case 2:

in the main function i have used the setStyleSheet and use it before the mainwindow's construct function

ui->setupUi(this);
    ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(0));
    ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(1));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(2));

ui->setupUi(this);
    ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(0));
    ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(1));
    //ui->treeWidget->setCurrentItem(ui->treeWidget->topLevelItem(2));

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the first the second and the last item height are UNNormal but the third is NORMAL
all the sub items are normal

case 3
i change the order of mainwindow's construct function and the setStyleSheet func

QApplication a(argc, argv);  
 
    MainWindow w;    //to here 
 
    QString str1;
    str1.append("uistyle.css");
    QFile file(str1);
 
    if(file.open(QFile::ReadOnly))
    {
        QString styleSheet = QObject::tr(file.readAll());
        a.setStyleSheet(styleSheet);
        file.close();
    }
 
    //MainWindow w;    //old position
    w.show();
    return a.exec();

QApplication a(argc, argv);  

    MainWindow w;    //to here 
    
    QString str1;
    str1.append("uistyle.css");
    QFile file(str1);

    if(file.open(QFile::ReadOnly))
    {
        QString styleSheet = QObject::tr(file.readAll());
        a.setStyleSheet(styleSheet);
        file.close();
    }

    //MainWindow w;    //old position
    w.show();
    return a.exec();

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all the item are normal

why? the attachment is follow