There is a bug in QT6.2.1. 

The pushButton Can not receive touch event after the widget that WindowFlags is Qt::Popup is closed on ubuntu20.04

I created a demo to reproduce it.

reproduce step:

1、Click the pushbutton with your finger to create a widget that WindowFlags is Qt::Popup.

2、Tap anywhere on the screen with your finger to close the widget.

3、Click the pushbutton with your finger again the pushbutton not responsed. But received these logs:

qt.pointer.dispatch: delivering touch update to same window QWidgetWindow(0x55c1cba8d280, name="QWidgetClassWindow") not QWidgetWindow(0x55c1cbc90130, name="MainWindowWindow")

qt.pointer.dispatch: delivering touch update to same window QWidgetWindow(0x55c1cba8d280, name="QWidgetClassWindow") not QWidgetWindow(0x55c1cbc90130, name="MainWindowWindow")

qt.pointer.dispatch: delivering touch update to same window QWidgetWindow(0x55c1cba8d280, name="QWidgetClassWindow") not QWidgetWindow(0x55c1cbc90130, name="MainWindowWindow") 

This is the debug information when the finger leaves the screen in the second step.

Because the widget which WindowFlags is Qt::Popup is closed when the touch pressed, the func 
platformWindowFromId(xcb_window_t id) will return NULL in here. It causes the func xi2ProcessTouch will not be called.

This is a log