(js) New sgCompile directive to render mail parts

UI/WebServerResources/js/Common/sgCompile.directive.js

@@ -0,0 +1,47 @@
+/* -*- Mode: javascript; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+
+(function() {
+  'use strict';
+
+  /*
+   * sgCompile - Assign an expression to a DOM element and compile it.
+   * @memberof SOGo.Common
+   * @restrict attribute
+   * @param {object} sgCompile - the expression to compile
+   * @ngInject
+   * @example:
+
+   <div sg-compile="part.content"><!-- msg --></div>
+  */
+  sgCompile.$inject = ['$compile'];
+  function sgCompile($compile) {
+    return {
+      restrict: 'A',
+      link: sgCompileLink
+    };
+
+    function sgCompileLink(scope, element, attrs) {
+      var ensureCompileRunsOnce = scope.$watch(
+        function(scope) {
+          // Watch the sg-compile expression for changes
+          return scope.$eval(attrs.sgCompile);
+        },
+        function(value) {
+          // When the sg-compile expression changes, assign it into the current DOM
+          element.html(value);
+          
+          // Compile the new DOM and link it to the current scope.
+          // NOTE: we only compile .childNodes so that we don't get into infinite loop compiling ourselves
+          $compile(element.contents())(scope);
+          
+          // Use un-watch feature to ensure compilation happens only once.
+          ensureCompileRunsOnce();
+        }
+      );
+    }
+  }
+
+  angular
+    .module('SOGo.Common')
+    .directive('sgCompile', sgCompile);
+})();