MacOS Window Z-level issue (regression)

See attached sample. Run and click in the modal dialog window. This will create a native OSX window. But if you drag this window over the dialog, it will appear beneath. In the worse scenario, the native window will open behind the dialog and will be invisible to the user.

This sample mimics a real-world application where an action in a Qt dialog, leads to opening a native third-party panel (non-Qt) under which the Qt application has no control.

This problem does not happen in Qt 4.8 (native window overlaps the dialog, as soon as clicking on it).

"It's like" if Qt 5.0 is watching the activation of any NSWindow, and put this window underneath the active modal dialog.