@Giorgi
MSDN said: To use SetWindowPos to bring a window to the top, the process that owns the window must have SetForegroundWindow permission.
eg.
#include <Windows.h>
SetForegroundWindow((HWND)winId());
setWindowFlags(Qt::WindowStaysOnTopHint);
// in .pro
win32-g++:LIBS += libUser32
win32-msvc*:LIBS += User32.lib