[libgweather/benzea/gnome-3-36-met.no-backport: 2/10] gweather: Only use 4 significant decimals for locations

[Benjamin Berg <bberg src gnome org>]

commit 2101d22ef4af9a858f7b0193223ef491c4c53c50
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Jan 7 12:46:34 2021 +0100

    gweather: Only use 4 significant decimals for locations
    
    1/1000th of a degree of longitude or latitude corresponds to around
    100 meters. There's no reason for the weather to be any more precise
    than this.
    
    See https://www.thoughtco.com/degree-of-latitude-and-longitude-distance-4070616
    
    Closes: #69

 libgweather/gweather-private.c | 16 ++++++++++++++++
 libgweather/gweather-private.h |  3 +++
 libgweather/test_libgweather.c |  1 +
 libgweather/weather-iwin.c     |  7 ++++---
 libgweather/weather-owm.c      |  7 ++++---
 libgweather/weather-yrno.c     |  7 ++++---
 6 files changed, 32 insertions(+), 9 deletions(-)
---
diff --git a/libgweather/gweather-private.c b/libgweather/gweather-private.c
index 3f7fdce6..0ccc21b3 100644
--- a/libgweather/gweather-private.c
+++ b/libgweather/gweather-private.c
@@ -22,3 +22,19 @@
 
 #include "gweather-private.h"
 
+/* sign, 3 digits, separator, 4 decimals, nul-char */
+#define DEGREES_STR_SIZE (1 + 3 + 1 + 4 + 1)
+
+char *
+_radians_to_degrees_str (gdouble radians)
+{
+  char *str;
+  double degrees;
+
+  str = g_malloc0 (DEGREES_STR_SIZE);
+  /* Max 4 decimals */
+  degrees = (double) ((int) (RADIANS_TO_DEGREES (radians) * 10000)) / 10000;
+  /* Too many digits */
+  g_return_val_if_fail (degrees <= 1000 || degrees >= -1000, NULL);
+  return g_ascii_formatd (str, G_ASCII_DTOSTR_BUF_SIZE, "%g", degrees);
+}
diff --git a/libgweather/gweather-private.h b/libgweather/gweather-private.h
index ddf0a41a..be73768e 100644
--- a/libgweather/gweather-private.h
+++ b/libgweather/gweather-private.h
@@ -167,6 +167,9 @@ struct _GWeatherInfoPrivate {
 #define RADIANS_TO_DEGREES(rad)                ((rad) * 180. / M_PI)
 #define RADIANS_TO_HOURS(rad)          ((rad) * 12. / M_PI)
 
+GWEATHER_EXTERN
+char           *_radians_to_degrees_str (gdouble radians);
+
 /*
  * Planetary Mean Orbit and their progressions from J2000 are based on the
  * values in http://ssd.jpl.nasa.gov/txt/aprx_pos_planets.pdf
diff --git a/libgweather/test_libgweather.c b/libgweather/test_libgweather.c
index 8a219115..106d201c 100644
--- a/libgweather/test_libgweather.c
+++ b/libgweather/test_libgweather.c
@@ -780,6 +780,7 @@ main (int argc, char *argv[])
                  FALSE);
        set_gsettings ();
 
+       g_test_add_func ("/weather/radians-to-degrees_str", test_radians_to_degrees_str);
        g_test_add_func ("/weather/named-timezones", test_named_timezones);
        g_test_add_func ("/weather/named-timezones-deserialized", test_named_timezones_deserialized);
        g_test_add_func ("/weather/no-code-serialize", test_no_code_serialize);
diff --git a/libgweather/weather-iwin.c b/libgweather/weather-iwin.c
index c3d414de..71020396 100644
--- a/libgweather/weather-iwin.c
+++ b/libgweather/weather-iwin.c
@@ -353,7 +353,8 @@ iwin_start_open (GWeatherInfo *info)
     SoupMessage *msg;
     struct tm tm;
     time_t now;
-    gchar latstr[G_ASCII_DTOSTR_BUF_SIZE], lonstr[G_ASCII_DTOSTR_BUF_SIZE];
+    g_autofree char *latstr = NULL;
+    g_autofree char *lonstr = NULL;
 
     g_assert (info != NULL);
 
@@ -376,8 +377,8 @@ iwin_start_open (GWeatherInfo *info)
     now = time (NULL);
     localtime_r (&now, &tm);
 
-    g_ascii_dtostr (latstr, sizeof(latstr), RADIANS_TO_DEGREES (loc->latitude));
-    g_ascii_dtostr (lonstr, sizeof(lonstr), RADIANS_TO_DEGREES (loc->longitude));
+    latstr = _radians_to_degrees_str (loc->latitude);
+    lonstr = _radians_to_degrees_str (loc->longitude);
     url = g_strdup_printf 
("https://www.weather.gov/forecasts/xml/sample_products/browser_interface/ndfdBrowserClientByDay.php?&lat=%s&lon=%s&format=24+hourly&startDate=%04d-%02d-%02d&numDays=7";,
                           latstr, lonstr, 1900 + tm.tm_year, 1 + tm.tm_mon, tm.tm_mday);
     g_debug ("iwin_start_open, requesting: %s", url);
diff --git a/libgweather/weather-owm.c b/libgweather/weather-owm.c
index a58950c9..eb45f52f 100644
--- a/libgweather/weather-owm.c
+++ b/libgweather/weather-owm.c
@@ -428,7 +428,8 @@ owm_start_open (GWeatherInfo *info)
     gchar *url;
     SoupMessage *message;
     WeatherLocation *loc;
-    gchar latstr[G_ASCII_DTOSTR_BUF_SIZE], lonstr[G_ASCII_DTOSTR_BUF_SIZE];
+    g_autofree char *latstr = NULL;
+    g_autofree char *lonstr = NULL;
 
     priv = info->priv;
     loc = &priv->location;
@@ -438,8 +439,8 @@ owm_start_open (GWeatherInfo *info)
 
     /* see the description here: http://bugs.openweathermap.org/projects/api/wiki/Api_2_5_forecast */
 
-    g_ascii_dtostr (latstr, sizeof(latstr), RADIANS_TO_DEGREES (loc->latitude));
-    g_ascii_dtostr (lonstr, sizeof(lonstr), RADIANS_TO_DEGREES (loc->longitude));
+    latstr = _radians_to_degrees_str (loc->latitude);
+    lonstr = _radians_to_degrees_str (loc->longitude);
 
 #define TEMPLATE_START "https://api.openweathermap.org/data/2.5/forecast?lat=%s&lon=%s&mode=xml&units=metric";
 #ifdef OWM_APIKEY
diff --git a/libgweather/weather-yrno.c b/libgweather/weather-yrno.c
index 8324121f..7834076f 100644
--- a/libgweather/weather-yrno.c
+++ b/libgweather/weather-yrno.c
@@ -435,7 +435,8 @@ yrno_start_open (GWeatherInfo *info)
     gchar *url;
     SoupMessage *message;
     WeatherLocation *loc;
-    gchar latstr[G_ASCII_DTOSTR_BUF_SIZE], lonstr[G_ASCII_DTOSTR_BUF_SIZE];
+    g_autofree char *latstr = NULL;
+    g_autofree char *lonstr = NULL;
 
     priv = info->priv;
     loc = &priv->location;
@@ -445,8 +446,8 @@ yrno_start_open (GWeatherInfo *info)
 
     /* see the description here: https://api.met.no/ */
 
-    g_ascii_dtostr (latstr, sizeof(latstr), RADIANS_TO_DEGREES (loc->latitude));
-    g_ascii_dtostr (lonstr, sizeof(lonstr), RADIANS_TO_DEGREES (loc->longitude));
+    latstr = _radians_to_degrees_str (loc->latitude);
+    lonstr = _radians_to_degrees_str (loc->longitude);
 
     url = g_strdup_printf("https://api.met.no/weatherapi/locationforecast/1.9/?lat=%s;lon=%s";, latstr, 
lonstr);
     g_debug ("yrno_start_open, requesting: %s", url);