From d8b5558699b47231eba2991fd4b0b7546a341f6d Mon Sep 17 00:00:00 2001
From: Steve Howell <showell30@yahoo.com>
Date: Thu, 10 Nov 2016 11:05:14 -0800
Subject: [PATCH] topic lists: Refactor handling of parent element.

The widget that gets built in topic_list.build_widget()
now knows how to add itself to its parent element and expose
an interface to retrieve the parent.
---
 frontend_tests/node_tests/topic_list.js |  8 +++++---
 static/js/topic_list.js                 | 25 +++++++++++++------------
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/frontend_tests/node_tests/topic_list.js b/frontend_tests/node_tests/topic_list.js
index cfea9ac49a..243f323aa0 100644
--- a/frontend_tests/node_tests/topic_list.js
+++ b/frontend_tests/node_tests/topic_list.js
@@ -30,13 +30,15 @@ global.compile_template('topic_list_item');
         return 1;
     };
 
-    var widget = topic_list.build_widget(stream, active_topic, max_topics);
+    var parent_elem = $('<div>');
+    var widget = topic_list.build_widget(parent_elem, stream, active_topic, max_topics);
     var topic_html = widget.get_dom();
 
+    assert.equal(widget.get_parent(), parent_elem);
+
     var topic = $(topic_html).find('a').text().trim();
     assert.equal(topic, 'coding');
 
-    var output_html = '<div>' + topic_html.html() + '</div>';
-    global.write_test_output("test_topic_list_build_widget", topic_html.html());
+    global.write_test_output("test_topic_list_build_widget", parent_elem.html());
 }());
 
diff --git a/static/js/topic_list.js b/static/js/topic_list.js
index 72f2db19c1..b7021d35fd 100644
--- a/static/js/topic_list.js
+++ b/static/js/topic_list.js
@@ -33,7 +33,7 @@ exports.set_count = function (stream_name, topic, count) {
     }
 };
 
-exports.build_widget = function (stream, active_topic, max_topics) {
+exports.build_widget = function (parent_elem, stream, active_topic, max_topics) {
     var self = {};
     self.topic_items = new Dict({fold_case: true});
 
@@ -86,6 +86,10 @@ exports.build_widget = function (stream, active_topic, max_topics) {
         return ul;
     }
 
+    self.get_parent = function () {
+        return parent_elem;
+    };
+
     self.is_for_stream = function (stream_name) {
         return stream === stream_name;
     };
@@ -124,6 +128,13 @@ exports.build_widget = function (stream, active_topic, max_topics) {
 
     self.dom = build_list(stream, active_topic, max_topics);
 
+    parent_elem.append(self.dom);
+
+    if (active_topic) {
+        self.activate_topic(active_topic);
+    }
+
+
     return self;
 };
 
@@ -131,18 +142,8 @@ exports.rebuild = function (stream_li, stream) {
     var max_topics = 5;
 
     var active_topic = narrow.topic();
-
     exports.remove_expanded_topics();
-
-    var widget = exports.build_widget(stream, active_topic, max_topics);
-
-    stream_li.append(widget.get_dom());
-
-    if (active_topic) {
-        widget.activate_topic(active_topic);
-    }
-
-    active_widget = widget; // set our global
+    active_widget = exports.build_widget(stream_li, stream, active_topic, max_topics);
 };
 
 // For zooming, we only do topic-list stuff here...let stream_list