[Bug 55374] New: user32:msg - test_swp_paint_region_on_show() sometimes gets a NULLREGION on Windows 7

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55374

Bug ID: 55374
           Summary: user32:msg - test_swp_paint_region_on_show() sometimes
                    gets a NULLREGION on Windows 7
           Product: Wine
           Version: unspecified
          Hardware: x86-64
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: user32
          Assignee: [e-mail]
          Reporter: [e-mail]

user32:msg - test_swp_paint_region_on_show() sometimes gets a NULLREGION on
Windows 7:

msg.c:9471: Test failed: GetRgnBox (on parent) returned 1
msg.c:9475: Test failed: parent update region: got (0,0)-(0,0), expected
(10,10)-(100,100)
msg.c:9508: Test failed: GetRgnBox (on parent) returned 1
msg.c:9512: Test failed: parent update region: got (0,0)-(0,0), expected
(20,20)-(120,120)

See https://test.winehq.org/data/patterns.html#user32:msg

The oldest known failure happened on 2023-06-22 and it has happened a bit over
once per week since, always on a w7u test configuration:
* 2023-06-22 win7_newtb-w7u-2qxl
* 2023-06-23 win7_newtb-w7u
* 2023-06-26 win7_newtb-w7u-2qxl
* 2023-07-13 win7_newtb-w7u-2qxl_1
* 2023-07-14 win7_newtb-w7u-de
* 2023-07-14 win7_newtb-w7u-de
* 2023-07-19 win7_newtb-w7u-es
* 2023-07-19 win7_newtb-w7u-es