angular dynamically adding contenteditable directive doesn't work? - angularjs

Question

Runnable CODE: my code
I try to dynamically add contenteditable directive to the <div> element when it is double-clicked.
when I put contenteditable directive to <div> in the beginning, the ng-model still work, but when I remove it and add it dynamically in ng-dblclick callback, ng-model seams not work anymore.
It's kind of like this Question.
but I can't think of a angular-friendly way to finish my work here.
How can I fix this?
code: html
<div ng-app="customControl">
<form name="myForm" ng-controller="mainControl">
<!-- Dynamically adding contenteditable directive : doesn't work -->
<div name="myWidget" ng-model="userContent" ng-click="enableEdit($event)"
strip-br="true"
required>Change me!</div>
<hr>
<textarea ng-model="userContent"></textarea>
</form>
</div>
code: js
angular.module('customControl', []).
controller('mainControl', function($scope) {
$scope.enableEdit = function(e) {
$(e.target).attr('contenteditable', '');
}
})
.directive('contenteditable', function() {
return {
restrict: 'A', // only activate on element attribute
require: '?ngModel', // get a hold of NgModelController
link: function(scope, element, attrs, ngModel) {
if(!ngModel) return; // do nothing if no ng-model
// Specify how UI should be updated
ngModel.$render = function() {
element.html(ngModel.$viewValue || '');
};
// Listen for change events to enable binding
element.on('keyup change', function() {
scope.$apply(read);
});
read(); // initialize
// Write data to the model
function read() {
var html = element.html();
// When we clear the content editable the browser
// leaves a <br> behind
// If strip-br attribute is provided then we strip this out
if( attrs.stripBr && html == '<br>' ) {
html = '';
}
ngModel.$setViewValue(html);
}
}
};
});