Where should parts of a custom AngularJS directive be kept?

I'm trying to create a custom Angular directive that uses KineticJS to draw on a canvas based off values in the scope. I intend to create a service that will then update the scope based off a $http call that receives a JSON response. At that point I'd like the directive to loop through the values in the scope and create a kinetic node for each value.

However, I'm not sure if I should be doing this inside the controller or within the link function of the directive. If I were to do the updating inside the linking function, would I scope.$watch or something else?

I've created the custom directive like this:

angular.module('history.directives', [])
    .directive('kinetic', function() {
        var kineticContainer = '<div id="container"></div>';
        return {
            restrict: 'E',
            compile:function (tElement, tAttrs, transclude) {
                tElement.html(kineticContainer);
            },
            controller: KineticCtrl
        };
});

The controller then looks like this:

function KineticCtrl($scope) {
    $scope.stage = new Kinetic.Stage({
        container: 'container',
        width: window.innerWidth,
        height: window.innerHeight - $('.navbar').outerHeight()
    });

    $scope.drawNode = function(posx, posy) {
        var layer = new Kinetic.Layer();
        var group = new Kinetic.Group({
            x: posx,
            y: posy
        });

        var line = new Kinetic.Line({
            points: [0, 25, 500, 25],
            stroke: 'black',
            strokeWidth: 4
        });

        var text = new Kinetic.Text({
            text: 'www.google.com',
            fontSize: 18,
            fontFamily: 'FontAwesome',
            fill: '#555',
            width: 300
        });

        group.add(line);
        group.add(text);
        layer.add(group);
        $scope.stage.add(layer);
    };

    $scope.drawNode(200, 400);
    $scope.drawNode(800, 400);
    $scope.drawNode(400, 100);
}

Any help would be appreciated!