http://bugs.winehq.org/show_bug.cgi?id=2057
--- Comment #17 from Dylan Smith dylan.ah.smith@gmail.com 2008-10-19 03:41:35 --- Created an attachment (id=16733) --> (http://bugs.winehq.org/attachment.cgi?id=16733) richedit: Implement WM_SETREDRAW with DefWindowProc
After doing some more tests with native riched20, and the relay trace, I found that it was using InvalidateRect and UpdateWindow while redraw is disabled. I also found that the DefWindowProc was being used in native richedit, but not in Wine. It seems as if redraw is simply done using DefWindowProc, which just clears the WS_VISIBLE flag to avoid redrawing the window.
When the richedit control becomes visible again by WM_SETREDRAW, it will be repainted properly, so it will fix the bug my last patch introduced by making sure the scrollbar is repainted.