in Xlib, we have Window; in Qt, what we have ???

[dzh1121]

Dear All,

in Xlib, we have Window class, to specify a Window a defined window.
In Qt, how could I get this argument?

Note: I need to use the XISelectEvents. for XI2 events.

my efforts:

Currently, I'' using

win = QX11Info::appRootWindow();

win = QX11Info::appRootWindow();

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. according to its definition, it is not the window of my created program.
I've also tried

win = QX11Info::appScreen();

win = QX11Info::appScreen();

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. and

win = Qt::Window;

win = Qt::Window;

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But both report "XError: BadWindow"

I've read through the definition of QMainWindow, and Window Flag.
But no luck.

Thanks in advance for your suggestion/direction/teaching.