[Bug 43465] Unit Test: ComboBox Dropdown does not work if Style is set and no scrollbar required

https://bugs.winehq.org/show_bug.cgi?id=43465

--- Comment #3 from Fabian Maurer  ---
Just a small collection of what I found so far.

Issue seems to start at

scroll.c:1980
> SetWindowPos( hwnd, 0, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE
>                    | SWP_NOACTIVATE | SWP_NOZORDER | SWP_FRAMECHANGED | SWP_SHOWWINDOW );

This calls

winpos.c:1897
> wvrFlags = SendMessageW( pWinpos->hwnd, WM_NCCALCSIZE, TRUE, (LPARAM)&params );
>
> *pNewClientRect = params.rgrc[0];

After that pNewClientRect is (left: 1, top: 1, bottom: -1, right -17) leading
to those problems.  
However, these values are not set in wine, but in native code, at least as far
as I could tell.

Following hack gets it to work partially:
> wvrFlags = SendMessageW( pWinpos->hwnd, WM_NCCALCSIZE, TRUE, (LPARAM)&params );
>     if(params.rgrc[0].right < 0)
>         return 0;
>     *pNewClientRect = params.rgrc[0];