thermostat: show temperature in red if heater is on

soft/thermostat/src/zoneitem.cpp

@@ -47,10 +47,15 @@ void ZoneItem::refresh(void)
 {
 	QString text;
 
-	if ((m_temperature_value == FORCE_OFF) || !m_available)
+	if ((m_temperature_value == FORCE_OFF) || !m_available) {
 		text += QString("-");
-	else
+	} else {
+		if (m_heating_on)
+			text.append(QString("<font color=red>"));
 		text += QString::number(m_temperature_value);
+		if (m_heating_on)
+			text.append(QString("</font>"));
+	}
 	text += QString("°C / ");
 
 	if (m_target_temperature == FORCE_OFF) {