Qt::FramelessWindowHint is invalid if packaged with AppImage

I want to build a window that no frame, so I use that code:

setWindowFlags(Qt::FramelessWindowHint | windowFlags());

it's work, but when I build with AppImage, it becomes invalid。

The complete constructor looks like this：

GWidget::GWidget(QWidget *parent)
        : QWidget(parent)
{
    setWindowFlags(Qt::FramelessWindowHint | windowFlags());
    setAttribute(Qt::WA_TranslucentBackground);
}

I try to Google,I find that maybe related to Window Manager, But I still can't solve this problem.

Who can help me?