Revert setlocale() effect as soon as possible. Closes #12.

The Xlib and ncurses libraries query the LC_CTYPE locale value to guess
the usable character set. If the calling program did not call setlocale(),
that character set will be severely limited. Extensive Unicode support
is a reasonable libcaca user expectation.

The locale is restored as soon as possible, once the window or terminal
have been initialised. Unfortunately, the effect of setlocale() is process-
wide, and may affect other threads. This is now documented.

Note also that both Xlib and ncurses ignore the effects of uselocale()
which would have been the thread-safe solution to this problem.

.gitignore

@@ -26,6 +26,7 @@ INSTALL
 caca-config
 # Testsuite binaries
 caca/t/bench
+caca/t/bug-setlocale
 caca/t/caca-test
 caca/t/simple
 caca/t/*.log

caca/caca.c

@@ -56,6 +56,12 @@ static int caca_plugin_install(caca_display_t *, char const *);
  *  retrieved using caca_get_canvas() and it is automatically destroyed when
  *  caca_free_display() is called.
  *
+ *  Note that in order to achieve maximum Unicode compatibility, the driver
+ *  initialisation code may temporarily change the program’s global LC_CTYPE
+ *  locale using setlocale(). It is advised not to call LC_CTYPE-dependent
+ *  functions from other threads during the call to caca_create_display().
+ *  The locale settings are restored when the function returns.
+ *
  *  See also caca_create_display_with_driver().
  *
  *  If an error occurs, NULL is returned and \b errno is set accordingly:

caca/driver/ncurses.c

@@ -228,6 +228,9 @@ static int ncurses_init_graphics(caca_display_t *dp)
         COLOR_WHITE + 8
     };
 
+#if defined HAVE_LOCALE_H
+    char const *old_locale;
+#endif
     mmask_t newmask;
     int fg, bg, max;
 
@@ -242,13 +245,16 @@ static int ncurses_init_graphics(caca_display_t *dp)
     signal(SIGWINCH, sigwinch_handler);
 #endif
 
-#if defined HAVE_LOCALE_H
-    setlocale(LC_ALL, "");
-#endif
-
     _caca_set_term_title("caca for ncurses");
 
+#if defined HAVE_LOCALE_H
+    old_locale = setlocale(LC_CTYPE, "");
+#endif
     initscr();
+#if defined HAVE_LOCALE_H
+    setlocale(LC_CTYPE, old_locale);
+#endif
+
     keypad(stdscr, TRUE);
     nonl();
     raw();

caca/driver/x11.c

@@ -106,13 +106,22 @@ static int x11_init_graphics(caca_display_t *dp)
     dp->resize.allow = 0;
 
 #if defined HAVE_LOCALE_H
-    setlocale(LC_ALL, "");
+    /* FIXME: some better code here would be:
+     * locale_t old_locale = uselocale(newlocale(LC_CTYPE_MASK,
+     *                                           "", (locale_t)0);
+     * … but XOpenDisplay only works properly with setlocale(),
+     * not uselocale(). */
+    char const *old_locale = setlocale(LC_CTYPE, "");
 #endif
 
     dp->drv.p->dpy = XOpenDisplay(NULL);
     if(dp->drv.p->dpy == NULL)
         return -1;
 
+#if defined HAVE_LOCALE_H
+    setlocale(LC_CTYPE, old_locale);
+#endif
+
 #if defined HAVE_GETENV
     fonts[0] = getenv("CACA_FONT");
     if(fonts[0] && *fonts[0])

caca/t/Makefile.am

@@ -10,7 +10,7 @@ endif
 
 EXTRA_DIST = check-copyright check-doxygen check-source check-win32
 
-noinst_PROGRAMS = simple bench $(cppunit_tests)
+noinst_PROGRAMS = simple bench bug-setlocale $(cppunit_tests)
 
 TESTS = simple check-copyright check-source check-win32 \
         $(doxygen_tests) $(cppunit_tests)
@@ -21,6 +21,9 @@ simple_LDADD = ../libcaca.la
 bench_SOURCES = bench.c
 bench_LDADD = ../libcaca.la
 
+bug_setlocale_SOURCES = bug-setlocale.c
+bug_setlocale_LDADD = ../libcaca.la
+
 caca_test_SOURCES = caca-test.cpp canvas.cpp dirty.cpp driver.cpp export.cpp
 caca_test_CXXFLAGS = $(CPPUNIT_CFLAGS)
 caca_test_LDADD = ../libcaca.la $(CPPUNIT_LIBS)

caca/t/bug-setlocale.c

@@ -0,0 +1,63 @@
+/*
+ *  bug-setlocale: unit test for wrong setlocale() calls
+ *  Copyright (c) 2016 Sam Hocevar <sam@hocevar.net>
+ *                All Rights Reserved
+ *
+ *  This program is free software. It comes without any warranty, to
+ *  the extent permitted by applicable law. You can redistribute it
+ *  and/or modify it under the terms of the Do What the Fuck You Want
+ *  to Public License, Version 2, as published by Sam Hocevar. See
+ *  http://www.wtfpl.net/ for more details.
+ */
+
+#include "config.h"
+
+#if !defined(__KERNEL__)
+#   include <stdio.h>
+#   include <stdlib.h>
+#   include <string.h>
+#endif
+
+#include "caca.h"
+
+#define TEST(x) \
+    do \
+    { \
+        tests++; \
+        if((x)) \
+            passed++; \
+        else \
+            fprintf(stderr, "test #%i failed: %s\n", (tests), #x); \
+    } \
+    while(0)
+
+int main(int argc, char *argv[])
+{
+    char buf[10];
+    char const * const * list;
+
+    list = caca_get_display_driver_list();
+
+    int i, tests = 0, passed = 0;
+
+    snprintf(buf, 10, "%.1f", 0.0f);
+    TEST(buf[1] == '.');
+
+    for (i = 0; list[i]; i += 2)
+    {
+        if (!strcmp(list[i], "x11") || !strcmp(list[i], "ncurses"))
+        {
+            caca_display_t *dp = caca_create_display_with_driver(NULL, list[i]);
+
+            snprintf(buf, 10, "%.1f", 0.0f);
+            TEST(buf[1] == '.');
+
+            caca_free_display(dp);
+        }
+    }
+
+    fprintf(stderr, "%i tests, %i errors\n", tests, tests - passed);
+
+    return 0;
+}
+

caca/t/simple.c

@@ -26,7 +26,7 @@
         if((x)) \
             passed++; \
         else \
-            fprintf(stderr, "test #%i failed\n", (tests)); \
+            fprintf(stderr, "test #%i failed: %s\n", (tests), #x); \
     } \
     while(0)