https://bugs.winehq.org/show_bug.cgi?id=42038
--- Comment #8 from Bernhard Übelacker bernhardu@mailbox.org --- Thank you very much taking care of this issue.
I tested with your patch on top of wine-5.0-rc4-57-g2100353861 with WinMerge-2.16.4-Setup.exe.
The scrollbars get activated as the first character is entered into the new compare.
That far the bug could be closed then for me, if that patch would be committed.
However, there seems to be still a difference to running inside native windows: there the scrollbars are enabled just when the new compare got opened. Wine with your patch needs to have additionally a character entered. But at least for WinMerge this is no issue as an empty compare serves no purpose.
But this difference could be related to the visibility issue you found, I guess?
With comparing files I could not find a difference between Wine with your patch and native.