I18N: Set C++ locale and format sizes according to the locale

Displaying a package size, an installation size, a download speed etc.
formats decimal numbers to 1-digit precision after the decimal point
(49.5 KiB). However, users expect the number to be formatted according
their locale. E.g. in cs_CZ.UTF-8, it is "49,5 KiB".

DNF5 formats these values with fmt::format() which utilizes C++ locale
if "L" formatting option is used.

C++ locale (std::locale::global()) and C locale (setlocale(),
C++-wrapped as std::setlocale()) are two different things and DNF5
only has set the C locale up to now.

This patch starts setting C++ locale, which also implicitly sets
C locale. This patch also modifies
libdnf5::cli::utils::units::format_size_aligned() to use the
locale-dependent decimal seperator (available since fmt-8.0.0).

I manually tested dnf5 and dnf5daemon-client and they work for me.

Though there is a risk that the new C++ locale will affect some code
uknown to me, like regular expression matching, or thread-specific
locales. If the affected code was unfixable, we can resort to saving
the desired C++ locale into a dedicated object accessible to
format_size_aligned() and pass it explicitly for fmt::format. Thorough
testing is welcome.

Related: rpm-software-management#1687

dnf5/main.cpp

@@ -77,14 +77,14 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 #include <libdnf5/utils/bgettext/bgettext-mark-domain.h>
 #include <libdnf5/utils/locker.hpp>
 #include <libdnf5/version.hpp>
-#include <locale.h>
 #include <string.h>
 
 #include <algorithm>
 #include <cmath>
 #include <cstring>
 #include <filesystem>
 #include <iostream>
+#include <locale>
 
 constexpr const char * DNF5_LOGGER_FILENAME = "dnf5.log";
 
@@ -940,11 +940,11 @@ static void print_new_leaves(Context & context) {
 }
 
 static void set_locale() {
-    auto * locale = setlocale(LC_ALL, "");
-    if (locale) {
-        return;
+    try {
+        std::locale::global(std::locale(""));
+    } catch (std::runtime_error & ex) {
+        std::cerr << "Failed to set locale, defaulting to \"C\"" << std::endl;
     }
-    std::cerr << "Failed to set locale, defaulting to \"C\"" << std::endl;
 }
 
 }  // namespace dnf5

dnf5daemon-client/main.cpp

@@ -42,13 +42,13 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 #include <libdnf5/logger/stream_logger.hpp>
 #include <libdnf5/utils/bgettext/bgettext-lib.h>
 #include <libdnf5/utils/bgettext/bgettext-mark-domain.h>
-#include <locale.h>
 #include <string.h>
 
 #include <cstring>
 #include <filesystem>
 #include <fstream>
 #include <iostream>
+#include <locale>
 
 namespace dnfdaemon::client {
 
@@ -220,7 +220,11 @@ static void add_commands(Context & context) {
 int main(int argc, char * argv[]) {
     std::unique_ptr<sdbus::IConnection> connection;
 
-    setlocale(LC_ALL, "");
+    try {
+        std::locale::global(std::locale(""));
+    } catch (std::runtime_error & ext) {
+    }
+
 
     dnfdaemon::client::Context context;
 

libdnf5-cli/CMakeLists.txt

@@ -47,6 +47,9 @@ target_link_libraries(libdnf5-cli PRIVATE common)
 target_link_libraries(libdnf5-cli PUBLIC libdnf5)
 
 pkg_check_modules(LIBFMT REQUIRED fmt)
+if (LIBFMT_VERSION VERSION_LESS 8.0.0)
+    add_definitions(-DFMT_PRE_8)
+endif()
 list(APPEND LIBDNF5_CLI_PC_REQUIRES "${LIBFMT_MODULE_NAME}")
 target_link_libraries(libdnf5-cli PUBLIC ${LIBFMT_LIBRARIES})
 

libdnf5-cli/utils/units.cpp

@@ -52,7 +52,14 @@ std::pair<float, const char *> to_size(int64_t num) {
 
 std::string format_size_aligned(int64_t num) {
     auto [value, unit] = to_size(num);
-    return fmt::format("{0:.1f} {1:>3s}", value, unit);
+    return fmt::format(
+#ifdef FMT_PRE_8
+        "{0:.1f} {1:>3s}",
+#else
+        "{0:.1Lf} {1:>3s}",
+#endif
+        value,
+        unit);
 }
 
 

test/libdnf5-cli/utils/test_utf8.cpp

@@ -22,15 +22,15 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 
 #include "utils/utf8.hpp"
 
-#include <clocale>
+#include <locale>
 
 
 CPPUNIT_TEST_SUITE_REGISTRATION(UTF8Test);
 
 
 void UTF8Test::setUp() {
     // wide characters do not work at all until we set locales in the code
-    setlocale(LC_ALL, "C.UTF-8");
+    std::locale::global(std::locale("C.UTF-8"));
 
     hello_world_en = "Hello world!";
     hello_world_cs = "Ahoj světe!";