From 98a9cd06880e10627868df5d11b97578ba18abca Mon Sep 17 00:00:00 2001
From: Ulrich Telle <ulrich.telle@gmx.de>
Date: Sun, 15 Jan 2023 15:17:44 +0100
Subject: [PATCH] Don't ignore LC_XXX in
 wxUILocaleImpl::GetPreferredUILanguages()

Previously, if LANGUAGE was set, the other locale-related environment
variables (LC_ALL, LC_MESSAGES, LANG) were simply ignored, which seems
wrong as the user running the program after explicitly setting LC_ALL
expects it to use this locale and not en_US from the default value of
LANGUAGE on a typical Linux system using English.

So handle LANGUAGE as a source of supplementary information, but still
honour all the other environment variables. This goes against an
explicit GNU gettext manual recommendation, but this recommendation
seems to only make sense in the usual case, when the first element of
LANGUAGE is the same as LC_ALL/LANG value, but not when they differ.

See #23146.
---
 src/unix/uilocale.cpp | 45 ++++++++++++++++++++++++++++---------------
 1 file changed, 30 insertions(+), 15 deletions(-)

diff --git a/src/unix/uilocale.cpp b/src/unix/uilocale.cpp
index 11d084c474..c2a351c674 100644
--- a/src/unix/uilocale.cpp
+++ b/src/unix/uilocale.cpp
@@ -760,7 +760,29 @@ wxVector<wxString> wxUILocaleImpl::GetPreferredUILanguages()
     // When the preferred UI language is determined, the LANGUAGE environment
     // variable is the primary source of preference.
     // http://www.gnu.org/software/gettext/manual/html_node/Locale-Environment-Variables.html
-    //
+
+    // Since the first item in LANGUAGE is supposed to be equal to LANG resp LC_ALL,
+    // determine the default language based on the locale related environment variables
+    // as the first entry in the list of preferred languages.
+    wxString langFull;
+    wxString modifier;
+    if (GetLocaleFromEnvironment(langFull, modifier))
+    {
+        if (!modifier.empty())
+        {
+            // Locale name with modifier
+            if (const wxLanguageInfo* li = wxUILocale::FindLanguageInfo(langFull + modifier))
+            {
+                preferred.push_back(li->CanonicalName);
+            }
+        }
+        // Locale name without modifier
+        if (const wxLanguageInfo* li = wxUILocale::FindLanguageInfo(langFull))
+        {
+            preferred.push_back(li->CanonicalName);
+        }
+    }
+
     // The LANGUAGE variable may contain a colon separated list of language
     // codes in the order of preference.
     // http://www.gnu.org/software/gettext/manual/html_node/The-LANGUAGE-variable.html
@@ -780,26 +802,19 @@ wxVector<wxString> wxUILocaleImpl::GetPreferredUILanguages()
             return preferred;
         wxLogTrace(TRACE_I18N, " - LANGUAGE was set, but it didn't contain any languages recognized by the system");
     }
+    else
+    {
+        wxLogTrace(TRACE_I18N, " - LANGUAGE was not set or empty, check LC_ALL, LC_MESSAGES, and LANG");
+    }
 
-    wxLogTrace(TRACE_I18N, " - LANGUAGE was not set or empty, check LC_ALL, LC_MESSAGES, and LANG");
-
-    // first get the string identifying the language from the environment
-    wxString langFull,
-             modifier;
-    if (!GetLocaleFromEnvironment(langFull, modifier))
+    if (preferred.empty())
     {
         // no language specified, treat it as English
         langFull = "en_US";
+        preferred.push_back(langFull);
+        wxLogTrace(TRACE_I18N, " - LC_ALL, LC_MESSAGES, and LANG were not set or empty, use English");
     }
 
-    if (!modifier.empty())
-    {
-        // Locale name with modifier
-        preferred.push_back(langFull + modifier);
-    }
-    // Locale name without modifier
-    preferred.push_back(langFull);
-
     return preferred;
 }