WA_TransparentForMouseEvents ignores children

If a child of a widget obscures a parent widget, and that parent has the attribute WA_TransparentForMouseEvents set, mouse events that should be handled by the child widget are not directed to the child widget.

I believe the issue is that WA_TransparentForMouseEvents is checked too soon in QWidgetPrivate::childAt_helper. Here is a context diff for a tested fix.

***************

• • • 9580,9587 ****
      )) {
      if (ignoreChildrenInDestructor && w->data->in_destructor)
      continue;

• if (w->testAttribute(Qt::WA_TransparentForMouseEvents))
• continue;
  QPoint childPoint = w->mapFromParent(p);
  #ifdef Q_WS_MAC
  if (includeFrame && !w->geometry().contains(p))
  • • 9580,9585 ----
      ***************
    • 9589,9594 ****
    • 9587,9594 ----
      #endif
      if (QWidget *t = w->d_func()->childAt_helper(childPoint, ignoreChildrenInDestructor))
      return t;
      + if (w->testAttribute(Qt::WA_TransparentForMouseEvents))
      + continue;
      // if WMouseNoMask is set the widget mask is ignored, if
      // the widget has no mask then the WMouseNoMask flag has no
      // effect