https://bugs.winehq.org/show_bug.cgi?id=6682
--- Comment #56 from Artem S. Tashkinov t.artem@mailcity.com --- (In reply to Fabian Maurer from comment #55)
If it's of use, the commit that fixed the issue (for me, at least) was
commit 997d4ef44f0f9e2284f99d7ce9ec135d68b30c7b Author: Fabian Maurer dark.shadow4@web.de Date: Mon Feb 13 16:58:29 2017 +0100
user32: Send WM_NCPAINT and WM_ERASEBKGND when window is shown.
Have you moved the about window or overlaid it with something? It works that way. It won't work once you invoke it without doing anything else. Also your composite window manager might have interfered - I don't use one.
The issue at hand was that a newly shown windows didn't get a redraw message, this the image was missing. That also explains why it works when you move the window or overlay something. I don't really know why it doesn't work on your system. Maybe the tests I added in this commit can help gather insights?
If I understand this commit description correctly it _must_ fix the issue for all use cases yet clearly it doesn't. I know nothing about Win32 API but I've got a feeling something is going on that's not covered by this change and you, Wine developers, can easily figure it out by looking at Wine debug log. I can look at it for years and I won't understand anything.
And as a bug reporter and a person who wants to make Wine better I can only do what I'm knowledgeable to do like post logs and screenshots ;-)