[libgweather] GWeatherInfo: don't use LC_MESSAGES for default measure units

[Giovanni Campagna <gcampagna src gnome org>]

commit c9383cdec1ff6316746a0b20dd49aeec396dd308
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Tue Mar 26 16:41:09 2013 +0100

    GWeatherInfo: don't use LC_MESSAGES for default measure units
    
    GSettings translation uses gettext, which uses LC_MESSAGES, instead of
    the appropriate LC_MEASUREMENT category.
    To get that, we need to use nl_langinfo. The downside is that it only
    offers metric or imperial, rather than having more finegrained defaults
    for different countries.
    The choices implemented are Farenheit / miles / knots / inchHg for imperial,
    and Celsius / meters / km/h / mmHg for metric.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=695873

 libgweather/weather.c                  |  132 ++++++++++++++++++++++++--------
 schemas/org.gnome.GWeather.gschema.xml |   16 +---
 2 files changed, 105 insertions(+), 43 deletions(-)
---
diff --git a/libgweather/weather.c b/libgweather/weather.c
index e0cf27f..7868ee7 100644
--- a/libgweather/weather.c
+++ b/libgweather/weather.c
@@ -26,13 +26,9 @@
 #include <string.h>
 #include <ctype.h>
 #include <math.h>
-
-#ifdef HAVE_VALUES_H
-#include <values.h>
-#endif
-
 #include <time.h>
 #include <unistd.h>
+#include <langinfo.h>
 
 #include <gtk/gtk.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>
@@ -669,9 +665,39 @@ gweather_info_get_conditions (GWeatherInfo *info)
     return g_strdup(gweather_conditions_to_string (&info->priv->cond));
 }
 
+static gboolean
+is_locale_metric (void)
+{
+    const char *fmt;
+    fmt = nl_langinfo (_NL_MEASUREMENT_MEASUREMENT);
+
+    if (fmt && *fmt == 2)
+       return FALSE;
+    else
+       return TRUE;
+}
+
+static GWeatherTemperatureUnit
+temperature_unit_to_real (GWeatherTemperatureUnit unit)
+{
+    if (G_UNLIKELY (unit == GWEATHER_TEMP_UNIT_INVALID)) {
+       g_critical("Conversion to invalid temperature unit");
+       unit = GWEATHER_TEMP_UNIT_DEFAULT;
+    }
+
+    if (unit == GWEATHER_TEMP_UNIT_DEFAULT)
+       return is_locale_metric() ?
+           GWEATHER_TEMP_UNIT_CENTIGRADE :
+           GWEATHER_TEMP_UNIT_FAHRENHEIT;
+
+    return unit;
+}
+
 static gchar *
 temperature_string (gfloat temp_f, GWeatherTemperatureUnit to_unit, gboolean want_round)
 {
+    to_unit = temperature_unit_to_real (to_unit);
+
     switch (to_unit) {
     case GWEATHER_TEMP_UNIT_FAHRENHEIT:
        if (!want_round) {
@@ -703,10 +729,10 @@ temperature_string (gfloat temp_f, GWeatherTemperatureUnit to_unit, gboolean wan
 
     case GWEATHER_TEMP_UNIT_INVALID:
     case GWEATHER_TEMP_UNIT_DEFAULT:
-    default:
-       g_critical ("Conversion to illegal temperature unit: %d", to_unit);
-       return g_strdup(C_("temperature unit", "Unknown"));
+       g_assert_not_reached ();
     }
+
+    return NULL;
 }
 
 gchar *
@@ -810,9 +836,27 @@ gweather_info_get_apparent (GWeatherInfo *info)
     return temperature_string (apparent, g_settings_get_enum (priv->settings, TEMPERATURE_UNIT), FALSE);
 }
 
+static GWeatherSpeedUnit
+speed_unit_to_real (GWeatherSpeedUnit unit)
+{
+    if (G_UNLIKELY (unit == GWEATHER_SPEED_UNIT_INVALID)) {
+       g_critical("Conversion to invalid speed unit");
+       unit = GWEATHER_SPEED_UNIT_DEFAULT;
+    }
+
+    if (unit == GWEATHER_SPEED_UNIT_DEFAULT)
+       return is_locale_metric() ?
+           GWEATHER_SPEED_UNIT_KPH :
+           GWEATHER_SPEED_UNIT_KNOTS;
+
+    return unit;
+}
+
 static gchar *
 windspeed_string (gfloat knots, GWeatherSpeedUnit to_unit)
 {
+    to_unit = speed_unit_to_real (to_unit);
+
     switch (to_unit) {
     case GWEATHER_SPEED_UNIT_KNOTS:
        /* TRANSLATOR: This is the wind speed in knots */
@@ -833,9 +877,7 @@ windspeed_string (gfloat knots, GWeatherSpeedUnit to_unit)
        return g_strdup_printf(_("Beaufort force %.1f"), WINDSPEED_KNOTS_TO_BFT (knots));
     case GWEATHER_SPEED_UNIT_INVALID:
     case GWEATHER_SPEED_UNIT_DEFAULT:
-    default:
-       g_critical ("Conversion to illegal speed unit: %d", to_unit);
-       return g_strdup(C_("speed unit", "Unknown"));
+       g_assert_not_reached ();
     }
 
     return NULL;
@@ -870,10 +912,27 @@ gweather_info_get_wind (GWeatherInfo *info)
     }
 }
 
+static GWeatherPressureUnit
+pressure_unit_to_real (GWeatherPressureUnit unit)
+{
+    if (G_UNLIKELY (unit == GWEATHER_PRESSURE_UNIT_INVALID)) {
+       g_critical("Conversion to invalid pressure unit");
+       unit = GWEATHER_PRESSURE_UNIT_DEFAULT;
+    }
+
+    if (unit == GWEATHER_PRESSURE_UNIT_DEFAULT)
+       return is_locale_metric() ?
+           GWEATHER_PRESSURE_UNIT_MM_HG :
+           GWEATHER_PRESSURE_UNIT_INCH_HG;
+
+    return unit;
+}
+
 gchar *
 gweather_info_get_pressure (GWeatherInfo *info)
 {
     GWeatherInfoPrivate *priv;
+    GWeatherPressureUnit unit;
 
     g_return_val_if_fail (GWEATHER_IS_INFO (info), NULL);
 
@@ -884,7 +943,8 @@ gweather_info_get_pressure (GWeatherInfo *info)
     if (priv->pressure < 0.0)
         return g_strdup(C_("pressure", "Unknown"));
 
-    switch (g_settings_get_enum (priv->settings, PRESSURE_UNIT)) {
+    unit = pressure_unit_to_real (g_settings_get_enum (priv->settings, PRESSURE_UNIT));
+    switch (unit) {
     case GWEATHER_PRESSURE_UNIT_INCH_HG:
        /* TRANSLATOR: This is pressure in inches of mercury */
        return g_strdup_printf(_("%.2f inHg"), priv->pressure);
@@ -906,18 +966,33 @@ gweather_info_get_pressure (GWeatherInfo *info)
 
     case GWEATHER_PRESSURE_UNIT_INVALID:
     case GWEATHER_PRESSURE_UNIT_DEFAULT:
-    default:
-       g_critical ("Conversion to illegal pressure unit");
-       return g_strdup(C_("pressure unit", "Unknown"));
+       g_assert_not_reached ();
     }
 
     return NULL;
 }
 
+static GWeatherDistanceUnit
+distance_unit_to_real (GWeatherDistanceUnit unit)
+{
+    if (G_UNLIKELY (unit == GWEATHER_DISTANCE_UNIT_INVALID)) {
+       g_critical("Conversion to invalid distance unit");
+       unit = GWEATHER_DISTANCE_UNIT_DEFAULT;
+    }
+
+    if (unit == GWEATHER_DISTANCE_UNIT_DEFAULT)
+       return is_locale_metric() ?
+           GWEATHER_DISTANCE_UNIT_METERS :
+           GWEATHER_DISTANCE_UNIT_MILES;
+
+    return unit;
+}
+
 gchar *
 gweather_info_get_visibility (GWeatherInfo *info)
 {
     GWeatherInfoPrivate *priv;
+    GWeatherDistanceUnit unit;
 
     g_return_val_if_fail (GWEATHER_IS_INFO (info), NULL);
     priv = info->priv;
@@ -927,7 +1002,8 @@ gweather_info_get_visibility (GWeatherInfo *info)
     if (priv->visibility < 0.0)
         return g_strdup (C_("visibility", "Unknown"));
 
-    switch (g_settings_get_enum (priv->settings, DISTANCE_UNIT)) {
+    unit = distance_unit_to_real (g_settings_get_enum (priv->settings, DISTANCE_UNIT));
+    switch (unit) {
     case GWEATHER_DISTANCE_UNIT_MILES:
        /* TRANSLATOR: This is the visibility in miles */
        return g_strdup_printf (_("%.1f miles"), priv->visibility);
@@ -940,9 +1016,7 @@ gweather_info_get_visibility (GWeatherInfo *info)
 
     case GWEATHER_DISTANCE_UNIT_INVALID:
     case GWEATHER_DISTANCE_UNIT_DEFAULT:
-    default:
-       g_critical ("Conversion to illegal visibility unit");
-       return g_strdup (C_("visibility unit", "Unknown"));
+       g_assert_not_reached ();
     }
 
     return NULL;
@@ -1372,6 +1446,7 @@ temperature_value (gdouble temp_f,
 
     if (to_unit == GWEATHER_TEMP_UNIT_DEFAULT)
            to_unit = g_settings_get_enum (settings, TEMPERATURE_UNIT);
+    to_unit = temperature_unit_to_real (to_unit);
 
     switch (to_unit) {
         case GWEATHER_TEMP_UNIT_FAHRENHEIT:
@@ -1385,9 +1460,7 @@ temperature_value (gdouble temp_f,
            break;
         case GWEATHER_TEMP_UNIT_INVALID:
         case GWEATHER_TEMP_UNIT_DEFAULT:
-       default:
-           ok = FALSE;
-           break;
+           g_assert_not_reached ();
     }
 
     return ok;
@@ -1408,6 +1481,7 @@ speed_value (gdouble            knots,
 
     if (to_unit == GWEATHER_SPEED_UNIT_DEFAULT)
            to_unit = g_settings_get_enum (settings, SPEED_UNIT);
+    to_unit = speed_unit_to_real (to_unit);
 
     switch (to_unit) {
         case GWEATHER_SPEED_UNIT_KNOTS:
@@ -1427,9 +1501,7 @@ speed_value (gdouble            knots,
            break;
         case GWEATHER_SPEED_UNIT_INVALID:
         case GWEATHER_SPEED_UNIT_DEFAULT:
-        default:
-            ok = FALSE;
-            break;
+           g_assert_not_reached ();
     }
 
     return ok;
@@ -1450,6 +1522,7 @@ pressure_value (gdouble               inHg,
 
     if (to_unit == GWEATHER_PRESSURE_UNIT_DEFAULT)
            to_unit = g_settings_get_enum (settings, PRESSURE_UNIT);
+    to_unit = pressure_unit_to_real (to_unit);
 
     switch (to_unit) {
         case GWEATHER_PRESSURE_UNIT_INCH_HG:
@@ -1472,9 +1545,7 @@ pressure_value (gdouble               inHg,
            break;
         case GWEATHER_PRESSURE_UNIT_INVALID:
         case GWEATHER_PRESSURE_UNIT_DEFAULT:
-        default:
-           ok = FALSE;
-           break;
+           g_assert_not_reached ();
     }
 
     return ok;
@@ -1495,6 +1566,7 @@ distance_value (gdouble               miles,
 
     if (to_unit == GWEATHER_DISTANCE_UNIT_DEFAULT)
            to_unit = g_settings_get_enum (settings, DISTANCE_UNIT);
+    to_unit = distance_unit_to_real (to_unit);
 
     switch (to_unit) {
         case GWEATHER_DISTANCE_UNIT_MILES:
@@ -1508,9 +1580,7 @@ distance_value (gdouble               miles,
             break;
         case GWEATHER_DISTANCE_UNIT_INVALID:
         case GWEATHER_DISTANCE_UNIT_DEFAULT:
-        default:
-           ok = FALSE;
-           break;
+           g_assert_not_reached ();
     }
 
     return ok;
diff --git a/schemas/org.gnome.GWeather.gschema.xml b/schemas/org.gnome.GWeather.gschema.xml
index 96d7d70..ca080cc 100644
--- a/schemas/org.gnome.GWeather.gschema.xml
+++ b/schemas/org.gnome.GWeather.gschema.xml
@@ -9,9 +9,7 @@
       </description>
     </key>
     <key name="temperature-unit" enum="org.gnome.GWeather.GWeatherTemperatureUnit">
-      <!-- TRANSLATORS: pick a temperature unit that should be used by default in your
-      locale; values must be quoted -->
-      <default l10n="messages">'fahrenheit'</default>
+      <default>'default'</default>
       <summary>Temperature unit</summary>
       <description>
        The unit of temperature used for showing weather. Valid values are 'kelvin',
@@ -19,9 +17,7 @@
       </description>
     </key>
     <key name="distance-unit" enum="org.gnome.GWeather.GWeatherDistanceUnit">
-      <!-- TRANSLATORS: pick a default distance unit for your locale, see key description
-      for valid values -->
-      <default l10n="messages">'miles'</default>
+      <default>'default'</default>
       <summary>Distance unit</summary>
       <description>
        The unit of distance used for showing weather (for example for visibility or for
@@ -29,9 +25,7 @@
       </description>
     </key>
     <key name="speed-unit" enum="org.gnome.GWeather.GWeatherSpeedUnit">
-      <!-- TRANSLATORS: pick a default speed unit for your locale, see key description
-      for valid values -->
-      <default l10n="messages">'knots'</default>
+      <default>'default'</default>
       <summary>Speed unit</summary>
       <description>
        The unit of speed used for showing weather (for example for wind speed). Valid
@@ -40,9 +34,7 @@
       </description>
     </key>
     <key name="pressure-unit" enum="org.gnome.GWeather.GWeatherPressureUnit">
-      <!-- TRANSLATORS: pick a default pressure unit for your locale, see key description
-      for valid values -->
-      <default l10n="messages">'inch-hg'</default>
+      <default>'default'</default>
       <summary>Pressure unit</summary>
       <description>
        The unit of pressure used for showing weather. Valid values are 'kpa' (kilopascal),