[Bug 7360] New: hiding child incorrectly sets an update region on the grandparent

[Wine Bugs]

http://bugs.winehq.org/show_bug.cgi?id=7360

Summary: hiding child incorrectly sets an update region on the
                    grandparent
           Product: Wine
           Version: 0.9.30.
          Platform: PC-x86-64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: wine-user
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

See attached sample code.  A grandparent top-level window is created.  A parent
window is made the child of the grandparent and occupies the entire space of the
grandparent.  A child window is made to occupy a small portion of its parent
window.  When ShowWindow(child, SW_HIDE) is called,
GetUpdateRect(grandparent...) gives a non-empty rect, when it should be empty.