From: Michael Tremer <michael.tremer@ipfire.org>
Date: Fri, 27 Mar 2026 12:30:01 +0000 (+0000)
Subject: graph: Fetch temperature unit from locale
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ab232b60272cfaad8faa564c597f189f43d15234;p=telemetry.git

graph: Fetch temperature unit from locale

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/daemon/graph.c b/src/daemon/graph.c
index 5319d93..6f98324 100644
--- a/src/daemon/graph.c
+++ b/src/daemon/graph.c
@@ -19,6 +19,7 @@
 #############################################################################*/
 
 #include <errno.h>
+#include <langinfo.h>
 #include <limits.h>
 #include <locale.h>
 #include <stdlib.h>
@@ -522,39 +523,44 @@ ERROR:
 }
 
 td_graph_temps td_graph_temperature(const td_graph_render_options* options) {
-	// These countries predominantly use Fahrenheit
-	const char* fahrenheit[] = {
-		// United States
-		"en_US",
-		// Bahamas
-		"en_BS",
-		// Belize
-		"en_BZ",
-		// Cayman Islands
-		"en_KY",
-		// Liberia
-		"en_LR",
-		// Palau
-		"en_PW",
-		// Marshall Islands
-		"en_MH",
-		// Micronesia
-		"en_FM",
-		NULL,
-	};
+	locale_t loc = NULL;
 
-	// If there is no locale, we will use Kelvin
-	if (!options->locale || !*options->locale || td_string_equals(options->locale, "C"))
-		return TD_GRAPH_TEMP_KELVIN;
+	// Use Kelvin by default
+	td_graph_temps t = TD_GRAPH_TEMP_KELVIN;
 
-	// Find anyone using Fahrenheit
-	for (const char** code = fahrenheit; *code; code++) {
-		if (td_string_startswith(options->locale, *code))
-			return TD_GRAPH_TEMP_FAHRENHEIT;
+	// If there is no locale, we will use Kelvin
+	if (!options->locale || !*options->locale)
+		goto DONE;
+
+	// Load the given locale
+	loc = newlocale(LC_MEASUREMENT_MASK, options->locale, (locale_t)0);
+	if (!loc)
+		goto DONE;
+
+	uint8_t measurement = (uint8_t)*nl_langinfo_l(_NL_MEASUREMENT_MEASUREMENT, loc);
+
+	// Select temperature measurement
+	switch (measurement) {
+		// Metric
+		case 1:
+			t = TD_GRAPH_TEMP_CELSIUS;
+			break;
+
+		// Imperial
+		case 2:
+			t = TD_GRAPH_TEMP_FAHRENHEIT;
+			break;
+
+		// Ignore anything else and stick with the default
+		default:
+			break;
 	}
 
-	// Otherwise use Celsius
-	return TD_GRAPH_TEMP_CELSIUS;
+DONE:
+	if (loc)
+		freelocale(loc);
+
+	return t;
 }
 
 int td_graph_vlabel_bps(td_ctx* ctx, td_graph* graph,