[Bug 37706] New: ScrollWindowEx() returns ERROR if the window is not visible (in the Windows API sense); real Windows returns NULLREGION

https://bugs.winehq.org/show_bug.cgi?id=37706

Bug ID: 37706
           Summary: ScrollWindowEx() returns ERROR if the window is not
                    visible (in the Windows API sense); real Windows
                    returns NULLREGION
           Product: Wine
           Version: 1.7.28
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: user32
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 50192
  --> https://bugs.winehq.org/attachment.cgi?id=50192
Sample program that demonstrates bug (source)

I'm using a dummy scroll (as in
http://blogs.msdn.com/b/oldnewthing/archive/2003/07/31/54601.aspx) to update
the scrollbars in my custom Windows control when necessary. In my test program,
this happens before the window is shown for the first time, and in wine, my
error checking code triggers because the ScrollWindowEx() call fails with
ERROR. This does not happen on real Windows; it instead returns NULLREGION.

The attached program creates several configurations that attempt to reproduce
this issue under different circumstances. On wine, I get

ScrollWindowEx() before ShowWindow(nCmdShow): ERROR
ScrollWindowEx() after ShowWindow(nCmdShow) and ShowWindow(SW_HIDE): ERROR
ScrollWindowEx() after only ShowWindow(nCmdShow): SIMPLEREGION

On Windows XP 32-bit, Windows 7 32-bit, and Windows 7 64-bit, I get

ScrollWindowEx() before ShowWindow(nCmdShow): NULLREGION
ScrollWindowEx() after ShowWindow(nCmdShow) and ShowWindow(SW_HIDE): NULLREGION
ScrollWindowEx() after only ShowWindow(nCmdShow): SIMPLEREGION

I can't find anything pointing to this use of ScrollWindowEx() being wrong... I
also do not know if any other scroll functions are equally affected.

I am running wine-1.7.28 from the Wine PPA on Ubuntu GNOME 14.10.

Thanks.