Re: [PATCH v5 0/2] MR7893: user32/tests: Test BeginPaint() clipbox of cropped window with CS_PARENTDC.

[Jinoh Kang (＠iamahuman)]

Jinoh Kang (@iamahuman) commented about dlls/user32/tests/msg.c:
> - check_lb_state(listbox, 0, LB_ERR, 0, 0);
> -
> - flush_sequence();
> -
> - log_all_parent_messages++;
> - log_painting_messages++;
> -
> - ret = GetWindowLongA(listbox, GWL_STYLE);
> - ok((ret & (WS_VSCROLL | WS_HSCROLL)) == 0, "Listbox should not have scroll bars\n");
> -
> - ret = SendMessageA(listbox, LB_SETCOUNT, 100, 0);
> - ok(ret == 0, "got %Id\n", ret);
> - ret = GetWindowLongA(listbox, GWL_STYLE);
> - ok((ret & (WS_VSCROLL | WS_HSCROLL)) == WS_VSCROLL, "Listbox should have vertical scroll bar\n");
> -
> - SendMessageA(listbox, WM_USER, 0, 0); /* Mark */

[MSDN][wu] says WM_USER is reserved for use in class-specific messages, so I'd shy away from using it for predefined controls like ListBox. I cannot find a precedent for using WM_USER as a marker in msg.c either.

Of course we could find guaranteed-unused ID or split seq, but I have a better idea: how about we test the invalidation / update region directly? We could use GetUpdateRect() or GetUpdateRgn() for that. Should be less flaky too.

[wu]: https://learn.microsoft.com/en-us/windows/win32/winmsg/wm-user