Add retain option to slider widget

mqtt_dash/static/main.js

@@ -133,9 +133,10 @@ function updateScroll() {
     element.scrollTop = element.scrollHeight;
 }
 
-function publish(topic, value) {
+function publish(topic, value, retain=false) {
     var message = new Paho.MQTT.Message(value);
     message.destinationName = topic;
+    message.retained = retain;
     client.send(message);
 }
 
@@ -159,7 +160,8 @@ function init(brokerUri) {
         slider.oninput = function() {
             this.onchange()
             var topic = this.getAttribute('data-pub-topic');
-            publish(topic, this.value);
+            var retain = Boolean(this.getAttribute('data-retain'));
+            publish(topic, this.value, retain);
         };
     }
 

mqtt_dash/widgets.py

@@ -49,7 +49,8 @@ def slider_widget(label,
                   unit='',
                   min_val=0,
                   max_val=255,
-                  step=1):
+                  step=1,
+                  retain=False):
     id_ = make_id()
     sub_topic = sub_topic or topic
     template = '''
@@ -58,6 +59,7 @@ def slider_widget(label,
       <input id="{{id_}}"
              class="slider update-policy-update-value {{sub_topic}}-value"
              data-pub-topic="{{topic}}"
+             data-retain="{{retain | string | lower}}"
              {% if value_path %} data-value-path="{{value_path}}" {% endif %}
              min="{{min_val}}" type="range" max="{{max_val}}" step="{{step}}"
              value="{{min_val}}"/>
@@ -76,6 +78,7 @@ def slider_widget(label,
                        value_path=value_path,
                        topic=topic,
                        unit=unit,
+                       retain=retain,
                        id_=id_)