QWindow::setParent() is documented to promise that the child window will be clipped to its parent, which we rely on in e.g. Qt Widgets when a native window is added to a scroll area. As of macOS 14 (if the app is built against the 14+ SDK), the default behavior changed from clipping to not clipping NSViews. We now explicitly opt back into the behavior, but try to be smart about it and only do it if we have potential child windows (since our own drawing should be correctly clipped to the window bounds). We could be even smarter and only consider QWindow based subviews, but if so we need to also account for foreign windows, which are not QNSViews. It's a bit unfortunate that we have to enable the clipping as broadly as this, as for e.g. WindowContainer in Qt Quick we use setMask to handle child window clipping, but for now this at least restores the behavior for Qt Widgets. [ChangeLog][macOS] QWindows with child windows will now set the NSView.clipsToBounds property to YES, to ensure that the child windows are clipped to their parent. Fixes: QTBUG-142664 Pick-to: 6.11 6.10 6.8 6.5 Change-Id: I352afcf1b664d29d928ac5b7e2c828ad757f28e7 Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>