http://bugs.winehq.org/show_bug.cgi?id=59034
--- Comment #7 from Andrew Nguyen arethusa26@gmail.com --- Thanks for looking into the issue and preparing a fix. I did some testing with your MR branch, and while I can confirm that the issue with the client area not rendering correctly no longer occurs for me, I now see a new issue that wasn't present before your fix.
Normally, if I try to close the main window, either by clicking on the close button on its title bar or selecting the File -> Exit menu option, I should see a modal message box asking "Do you want to Backup your datafile?" that takes focus and appears on top of the main window. The close button of the main window in the title bar also disappears, presumably to prevent it from being closed while the message box is displayed.
However, with your change, when I try to close the main window, it behaves as if the message box is being displayed, but there's no message box window that I can find, which makes proceeding with the close operation seemingly impossible.
Please let me know if I can provide any additional debug traces, as you reported difficulty with reproducing the original issue in your testing.