redesign PBD::LocaleGuard to work correctly (i.e. not break translations)

[ardour.git] / libs / pbd / locale_guard.cc

diff --git a/libs/pbd/locale_guard.cc b/libs/pbd/locale_guard.cc
index 7d6c0708b8a4cea030b09eacd2eeb75194b7c9d9..f5f97f20423c400f78079358236e69fb494ed0b0 100644 (file)
--- a/libs/pbd/locale_guard.cc
+++ b/libs/pbd/locale_guard.cc
@@ -1,22 +1,100 @@
+/*
+    Copyright (C) 2012 Paul Davis
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 #include <locale.h>
 
+#include "pbd/compose.h"
+#include "pbd/debug.h"
+#include "pbd/error.h"
 #include "pbd/locale_guard.h"
 
 using namespace PBD;
 
-LocaleGuard::LocaleGuard (const char* str)
+/* Neither C nor C++ pick up a user's preferred locale choice without the
+ * application actively taking steps to make this happen.
+ *
+ * For C: setlocale (LC_ALL, "");
+ * For C++ (assuming that the C version was called):
+ *      std::locale::global (std::locale (setlocale (LC_ALL, 0)));
+ *
+ * The application needs to make these calls, probably in main().
+ *
+ * Setting the C++ locale will change the C locale, but not the other way 'round.
+ * and some plugin may change either behind our back.
+ */
+
+LocaleGuard::LocaleGuard ()
+       : old_c_locale (0)
 {
-       old = strdup (setlocale (LC_NUMERIC, NULL));
-       if (strcmp (old, str)) {
-               setlocale (LC_NUMERIC, str);
+       /* A LocaleGuard object ensures that the
+        * LC_NUMERIC/std::locale::numeric aspect of the C and C++ locales are
+        * set to "C" during its lifetime, so that printf/iostreams use a
+        * portable format for numeric output (i.e. 1234.5 is always 1234.5 and
+        * not sometimes 1234,5, as it would be in fr or de locales)
+        */
+
+       char const * const current_c_locale = setlocale (LC_NUMERIC, 0);
+
+       if (strcmp ("C", current_c_locale) != 0) {
+
+               old_c_locale = strdup (current_c_locale);
+
+               /* set the C++ global/default locale to whatever we are using
+                * now, but with "C" numeric handling.
+                *
+                * this also sets the C locale, so no call to setlocale() is required.
+                */
+
+               std::locale::global (std::locale (old_cpp_locale, "C", std::locale::numeric));
+               pre_cpp_locale = std::locale();
+
+               DEBUG_TRACE (DEBUG::Locale, string_compose ("LG: change locale from '%1' => %2\n", old_cpp_locale.name(), pre_cpp_locale.name()));
        }
 }
 
 LocaleGuard::~LocaleGuard ()
 {
-       setlocale (LC_NUMERIC, old);
-       free ((char*)old);
-}
+       char const * current_c_locale = setlocale (LC_NUMERIC, 0);
+       std::locale current_cpp_locale;
+
+       if (current_cpp_locale != pre_cpp_locale) {
+
+               PBD::error << string_compose ("LocaleGuard: someone (a plugin) changed the C++ locale from\n\t%1\nto\n\t%2\n, expect non-portable session files. Decimal OK ? %2",
+                                             old_cpp_locale.name(), current_cpp_locale.name(),
+                                             (std::use_facet<std::numpunct<char> >(std::locale()).decimal_point() == '.'))
+                          << endmsg;
+               DEBUG_TRACE (DEBUG::Locale, string_compose ("LG: someone (a plugin) changed the C++ locale (Decimal OK ? '%1'); expect non-portable session files.\n",
+                                                           (std::use_facet<std::numpunct<char> >(std::locale()).decimal_point() == '.')));
 
+               /* this resets C & C++ locales */
+               std::locale::global (old_cpp_locale);
+               DEBUG_TRACE (DEBUG::Locale, string_compose ("LG: restore C & C++ locale: '%1'\n", std::locale().name()));
+
+       } else if (old_c_locale && (strcmp (current_c_locale, old_c_locale) != 0)) {
+
+               /* reset only the C locale */
+               setlocale (LC_NUMERIC, old_c_locale);
+               DEBUG_TRACE (DEBUG::Locale, string_compose ("LG: restore C locale from %1 to\n'%2'\n(C++ is '%3')\n", current_c_locale, old_c_locale, std::locale().name()));
+       }
+
+       free (const_cast<char*> (old_c_locale));
+}