QX11EmbedContainer not supporting drag and drop (dnd) correctly

(1) run frigdgemagnets example from here,
qt5/qtbase/examples/widgets/draganddrop/fridgemagnets

(2) use xwininfo to get its window ID

(3) build/run the windowGrabber program I attached

(4) enter/take the window ID reported in (2)

(5) attempt drag and drop

The drag and drop doesnt work correctly.
For correct behaviour, just follow the step 1 and do drag and drop.