Simplify code to generate new stream colors.

Instead of splicing up a cloned copy of stream_assignment_colors
every time somebody uses a color, we just rebuild a hash
of used_colors from our subscribed streams when we need to assign
a color, and we avoid calling into stream_color.pick_color() when
a stream already has a color.

This change has a slight functional impact in the situation where
a user unsubscribes some streams during their session, because
we weren't "reclaiming" colors before on unsubscription, but the
simple approach gets that for free.

(imported from commit adf360365bdf1ae9db99c533a0bde62d91f5dfe8)

static/js/stream_color.js

@@ -12,31 +12,28 @@ var stream_assignment_colors = ["#76ce90", "#fae589", "#a6c7e5", "#e79ab5",
                                 "#9987e1", "#e4523d", "#c2c2c2", "#4f8de4",
                                 "#c6a8ad", "#e7cc4d", "#c8bebf", "#a47462"];
 
-// Clone stream_assignement_colors
-var available_colors = stream_assignment_colors.slice(0);
-
 // Classes which could be returned by get_color_class.
 exports.color_classes = 'dark_background';
 
-exports.pick_color = function () {
+exports.pick_color = function (used_colors) {
-    if (available_colors.length === 0) {
+    var used_color_hash = {};
-        // We've used all the palette colors, so start re-using them.
+
-        return stream_assignment_colors[exports.subscribed_streams().length
+    _.each(used_colors, function (color) {
-                                        % stream_assignment_colors.length];
+        used_color_hash[color] = true;
+    });
+
+    var color = _.find(stream_assignment_colors, function (color) {
+        return !_.has(used_color_hash, color);
+    });
+
+    if (color) {
+        return color;
     }
 
-    return available_colors[0];
+    // All available colors were used.
+    return stream_assignment_colors[0];
 };
 
-exports.mark_color_used = function (color) {
-    var i;
-    for (i = 0; i < available_colors.length; ++i) {
-        if (available_colors[i] === color) {
-            available_colors.splice(i, 1);
-            return;
-        }
-    }
-};
 
 function update_table_stream_color(table, stream_name, color) {
     var color_class = exports.get_color_class(color);

static/js/subs.js

@@ -30,6 +30,14 @@ exports.subscribed_streams = function () {
         .value();
 };
 
+function get_color() {
+    var streams = _.values(stream_info);
+    var subscribed_streams = _.where(streams, {subscribed: true});
+    var used_colors = _.pluck(subscribed_streams, 'color');
+    var color = stream_color.pick_color(used_colors);
+    return color;
+}
+
 exports.update_all_messages_link = function () {
     // Show or hide the "All messages" link, depending on whether
     // the user has any subscriptions hidden from home view.
@@ -176,10 +184,12 @@ function create_sub(stream_name, attrs) {
         subscribed: true,
         in_home_view: true,
         invite_only: false,
-        notifications: false,
+        notifications: false
-        color: stream_color.pick_color()
     });
-    stream_color.mark_color_used(sub.color);
+
+    if (!sub.color) {
+        sub.color = get_color();
+    }
 
     add_sub(stream_name, sub);
     $(document).trigger($.Event('sub_obj_created.zulip', {sub: sub}));
@@ -229,9 +239,9 @@ function mark_subscribed(stream_name, attrs) {
         add_sub_to_table(sub);
     } else if (! sub.subscribed) {
         // Add yourself to an existing stream.
+        var color = get_color();
+        exports.set_color(stream_name, color);
         sub.subscribed = true;
-        exports.set_color(stream_name, stream_color.pick_color());
-        stream_color.mark_color_used(sub.color);
         var settings = settings_for_sub(sub);
         var button = button_for_sub(sub);
         if (button.length !== 0) {