[Bug 55446] New: Using C run-time for unicode strings comparison breaks case insensitive LB_FINDSTRING

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55446

Bug ID: 55446
           Summary: Using C run-time for unicode strings comparison breaks
                    case insensitive LB_FINDSTRING
           Product: Wine
           Version: 8.13
          Hardware: x86-64
                OS: Linux
            Status: NEW
          Keywords: regression
          Severity: normal
          Priority: P2
         Component: user32
          Assignee: [e-mail]
          Reporter: [e-mail]
                CC: [e-mail]
   Regression SHA1: 9cc92365560f19c2fd2b9796f79aa75e02381bb1
      Distribution: ---

If an application uses LB_FINDSTRING and provides a string that doesn't match
exactly then LB_FINDSTRING fails. This is a regression, and it's caused by

commit 9cc92365560f19c2fd2b9796f79aa75e02381bb1
Author: Alexandre Julliard 
Date:   Mon Sep 21 13:53:21 2020 +0200

user32: Build with msvcrt.

Signed-off-by: Alexandre Julliard

wcsnicmp() used by LB_FINDSTRING (in both user32 and comctl32) doesn't work
properly because it depends on LC_TYPE locale being correctly set, otherwise
_towlower_l() correctly handles only ASCII character range.

Relying on CRT locale being correctly initialized in a win32 core DLL seems
undesirable because an application may not use or care about C run-time at all.

Under Windows SendMessageW(LB_FINDSTRING) works just fine regardless of system
locale.

P.S.
This is a much more serious problem, and is not limited to user32/comctl32 
because wcsnicmp()/wcsicmp() is used everywhere in the Wine codebase.