IPython/html/static/notebook/js/widgets/container.js

require(["notebook/js/widget"], function(){
    var ContainerModel = IPython.WidgetModel.extend({});
    IPython.notebook.widget_manager.register_widget_model('ContainerWidgetModel', ContainerModel);

    var ContainerView = IPython.WidgetView.extend({
        
        render: function(){
            this.$el = $('<div />')
                .addClass('widget-container');
        },
        
        update: function(){

            // Apply flexible box model properties by adding and removing
            // corrosponding CSS classes.
            // Defined in IPython/html/static/base/less/flexbox.less
            this.set_flex_property('vbox', this.model.get('_vbox'));
            this.set_flex_property('hbox', this.model.get('_hbox'));
            this.set_flex_property('start', this.model.get('_pack_start'));
            this.set_flex_property('center', this.model.get('_pack_center'));
            this.set_flex_property('end', this.model.get('_pack_end'));
            this.set_flex_property('align_start', this.model.get('_align_start'));
            this.set_flex_property('align_center', this.model.get('_align_center'));
            this.set_flex_property('align_end', this.model.get('_align_end'));

            return IPython.WidgetView.prototype.update.call(this);
        },

        set_flex_property: function(property_name, enabled) {
            if (enabled) {
                this.$el.addClass(property_name);
            } else {
                this.$el.removeClass(property_name);
            }
        },

        display_child: function(view) {
            this.$el.append(view.$el);
        },
    });

    IPython.notebook.widget_manager.register_widget_view('ContainerView', ContainerView);
});