emacs-27 abedf3a: Fix language-environment and font selection on MS-Windows

[Eli Zaretskii]

branch: emacs-27
commit abedf3a8653829f5170ff72b2fc7adad0e6f80d4
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix language-environment and font selection on MS-Windows
    
    These changes improve setting the language-environment and font
    selection when MS-Windows returns useless "ZZZ" as the "language
    name", which then disrupts all the setup of the locale-dependent
    stuff, and in particular font selection.
    * lisp/w32-fns.el (w32-charset-info-alist): Add an element for
    "iso8859-5", in case LANG is set to something unusable, like
    "ZZZ".  This allows fonts capable of displaying Cyrillic
    characters to be used even when language preferences are screwed.
    
    * src/w32.c (init_environment): If GetLocaleInfo returns "ZZZ" as
    the "language name" for LOCALE_USER_DEFAULT, try again with locale
    ID based on what GetUserDefaultUILanguage returns.  (Bug#39286)
---
 lisp/w32-fns.el |  1 +
 src/w32.c       | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/lisp/w32-fns.el b/lisp/w32-fns.el
index eb12dcd..687afc8 100644
--- a/lisp/w32-fns.el
+++ b/lisp/w32-fns.el
@@ -252,6 +252,7 @@ bit output with no translation."
   (w32-add-charset-info "iso8859-2" 'w32-charset-easteurope 28592)
   (w32-add-charset-info "iso8859-3" 'w32-charset-turkish 28593)
   (w32-add-charset-info "iso8859-4" 'w32-charset-baltic 28594)
+  (w32-add-charset-info "iso8859-5" 'w32-charset-russian 28595)
   (w32-add-charset-info "iso8859-6" 'w32-charset-arabic 28596)
   (w32-add-charset-info "iso8859-7" 'w32-charset-greek 28597)
   (w32-add-charset-info "iso8859-8" 'w32-charset-hebrew 1255)
diff --git a/src/w32.c b/src/w32.c
index e6dffe2..d4f3192 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -346,6 +346,7 @@ static BOOL g_b_init_get_adapters_addresses;
 static BOOL g_b_init_reg_open_key_ex_w;
 static BOOL g_b_init_reg_query_value_ex_w;
 static BOOL g_b_init_expand_environment_strings_w;
+static BOOL g_b_init_get_user_default_ui_language;
 
 BOOL g_b_init_compare_string_w;
 BOOL g_b_init_debug_break_process;
@@ -533,6 +534,7 @@ DWORD multiByteToWideCharFlags;
 typedef LONG (WINAPI *RegOpenKeyExW_Proc) (HKEY,LPCWSTR,DWORD,REGSAM,PHKEY);
 typedef LONG (WINAPI *RegQueryValueExW_Proc) 
(HKEY,LPCWSTR,LPDWORD,LPDWORD,LPBYTE,LPDWORD);
 typedef DWORD (WINAPI *ExpandEnvironmentStringsW_Proc) (LPCWSTR,LPWSTR,DWORD);
+typedef LANGID (WINAPI *GetUserDefaultUILanguage_Proc) (void);
 
   /* ** A utility function ** */
 static BOOL
@@ -1489,6 +1491,28 @@ expand_environment_strings_w (LPCWSTR lpSrc, LPWSTR 
lpDst, DWORD nSize)
   return s_pfn_Expand_Environment_Strings_w (lpSrc, lpDst, nSize);
 }
 
+static LANGID WINAPI
+get_user_default_ui_language (void)
+{
+  static GetUserDefaultUILanguage_Proc s_pfn_GetUserDefaultUILanguage = NULL;
+  HMODULE hm_kernel32 = NULL;
+
+  if (is_windows_9x () == TRUE)
+    return 0;
+
+  if (g_b_init_get_user_default_ui_language == 0)
+    {
+      g_b_init_get_user_default_ui_language = 1;
+      hm_kernel32 = LoadLibrary ("Kernel32.dll");
+      if (hm_kernel32)
+       s_pfn_GetUserDefaultUILanguage = (GetUserDefaultUILanguage_Proc)
+         get_proc_addr (hm_kernel32, "GetUserDefaultUILanguage");
+    }
+  if (s_pfn_GetUserDefaultUILanguage == NULL)
+    return 0;
+  return s_pfn_GetUserDefaultUILanguage ();
+}
+
 
 
 /* Return 1 if P is a valid pointer to an object of size SIZE.  Return
@@ -2927,6 +2951,32 @@ init_environment (char ** argv)
                      LOCALE_SABBREVLANGNAME | LOCALE_USE_CP_ACP,
                      locale_name, sizeof (locale_name)))
     {
+      /* Microsoft are migrating away of locale IDs, replacing them
+        with locale names, such as "en-US", and are therefore
+        deprecating the APIs which use LCID etc.  As part of that
+        deprecation, they don't bother inventing LCID and LANGID
+        codes for new locales and language/culture combinations;
+        instead, those get LCID of 0xC000 and LANGID of 0x2000, for
+        which the LCID/LANGID oriented APIs return "ZZZ" as the
+        "language name".  Such "language name" is useless for our
+        purposes.  So we instead use the default UI language, in the
+        hope of getting something usable.  */
+      if (strcmp (locale_name, "ZZZ") == 0)
+       {
+         LANGID lang_id = get_user_default_ui_language ();
+
+         if (lang_id != 0)
+           {
+             /* Disregard the sorting order differences between cultures.  */
+             LCID def_lcid = MAKELCID (lang_id, SORT_DEFAULT);
+             char locale_name_def[32];
+
+             if (GetLocaleInfo (def_lcid,
+                                LOCALE_SABBREVLANGNAME | LOCALE_USE_CP_ACP,
+                                locale_name_def, sizeof (locale_name_def)))
+               strcpy (locale_name, locale_name_def);
+           }
+       }
       for (i = 0; i < N_ENV_VARS; i++)
         {
           if (strcmp (env_vars[i].name, "LANG") == 0)
@@ -10451,6 +10501,7 @@ globals_of_w32 (void)
   g_b_init_expand_environment_strings_w = 0;
   g_b_init_compare_string_w = 0;
   g_b_init_debug_break_process = 0;
+  g_b_init_get_user_default_ui_language = 0;
   num_of_processors = 0;
   /* The following sets a handler for shutdown notifications for
      console apps. This actually applies to Emacs in both console and