Add support for themes (fixes #1925)

gui/default/syncthing/core/syncthingController.js

@@ -866,6 +866,7 @@ angular.module('syncthing.core')
         $scope.saveSettings = function () {
             // Make sure something changed
             var changed = !angular.equals($scope.config.options, $scope.tmpOptions) || !angular.equals($scope.config.gui, $scope.tmpGUI);
+            var themeChanged = $scope.config.gui.theme !== $scope.tmpGUI.theme;
             if (changed) {
                 // Check if usage reporting has been enabled or disabled
                 if ($scope.tmpOptions.urEnabled && $scope.tmpOptions.urAccepted <= 0) {
@@ -901,6 +902,10 @@ angular.module('syncthing.core')
             }
 
             $('#settings').modal("hide");
+
+            if (themeChanged) {
+              document.location.reload(true);
+            }
         };
 
         $scope.saveAdvanced = function () {

gui/default/syncthing/settings/settingsModalView.html

@@ -136,8 +136,17 @@
                 <span class="fa fa-repeat"></span>&nbsp;<span translate>Generate</span>
               </button>
             </div>
-          </div>
 
+            <div class="form-group" ng-if="system.themes.length > 1">
+              <label>GUI Theme</label>
+              <select class="form-control" ng-model="tmpGUI.theme" ng->
+                <option ng-repeat="theme in system.themes" value="{{ theme }}">
+                  {{ theme.charAt(0).toUpperCase() + theme.slice(1) }}
+                </option>
+              </select>
+            </div>
+
+          </div>
         </div>
       </form>
     </div>