Use virtual-dom for rendering the drag and drop interface.

This patch also includes a change where the items are positioned
absolutely (rather than relatively) after dropping into the correct
zone, which means that after dropped into the zone, the element
no longer occupies vertical space in the item list on the left,
which is desired behaviour.

drag_and_drop_v2/default_data.py

-default_data = {
+DEFAULT_DATA = {
   "zones": [
     {
       "index": 1,

drag_and_drop_v2/drag_and_drop_v2.py

@@ -3,7 +3,6 @@
 
 # Imports ###########################################################
 
-import logging
 import json
 import webob
 import copy
@@ -14,12 +13,7 @@ from xblock.fields import Scope, String, Dict, Float, Boolean
 from xblock.fragment import Fragment
 
 from .utils import render_template, load_resource
-from .default_data import default_data
-
-
-# Globals ###########################################################
-
-log = logging.getLogger(__name__)
+from .default_data import DEFAULT_DATA
 
 
 # Classes ###########################################################
@@ -53,7 +47,7 @@ class DragAndDropBlock(XBlock):
         display_name="Drag and Drop",
         help="JSON spec as generated by the builder",
         scope=Scope.content,
-        default=default_data
+        default=DEFAULT_DATA
     )
 
     item_state = Dict(
@@ -75,30 +69,22 @@ class DragAndDropBlock(XBlock):
         Player view, displayed to the student
         """
 
-        js_templates = load_resource('/templates/html/js_templates.html')
-
-        context = {
-            'js_templates': js_templates,
-            'title': self.display_name,
-            'question_text': self.question_text,
-        }
-
         fragment = Fragment()
-        fragment.add_content(render_template('/templates/html/drag_and_drop.html', context))
-        CSS_URLS = (
+        fragment.add_content(render_template('/templates/html/drag_and_drop.html'))
+        css_urls = (
             'public/css/vendor/jquery-ui-1.10.4.custom.min.css',
             'public/css/drag_and_drop.css'
         )
-        JS_URLS = (
+        js_urls = (
             'public/js/vendor/jquery-ui-1.10.4.custom.min.js',
             'public/js/vendor/jquery-ui-touch-punch-0.2.3.min.js',  # Makes it work on touch devices
-            'public/js/vendor/jquery.html5-placeholder-shim.js',
-            'public/js/vendor/handlebars-v1.1.2.js',
+            'public/js/vendor/virtual-dom-1.3.0.min.js',
             'public/js/drag_and_drop.js',
+            'public/js/view.js',
         )
-        for css_url in CSS_URLS:
+        for css_url in css_urls:
             fragment.add_css_url(self.runtime.local_resource_url(self, css_url))
-        for js_url in JS_URLS:
+        for js_url in js_urls:
             fragment.add_javascript_url(self.runtime.local_resource_url(self, js_url))
 
         fragment.initialize_js('DragAndDropBlock')
@@ -119,18 +105,21 @@ class DragAndDropBlock(XBlock):
 
         fragment = Fragment()
         fragment.add_content(render_template('/templates/html/drag_and_drop_edit.html', context))
-        fragment.add_css_url(self.runtime.local_resource_url(self,
-            'public/css/vendor/jquery-ui-1.10.4.custom.min.css'))
-        fragment.add_css_url(self.runtime.local_resource_url(self,
-            'public/css/drag_and_drop_edit.css'))
-        fragment.add_javascript_url(self.runtime.local_resource_url(self,
-            'public/js/vendor/jquery-ui-1.10.4.custom.min.js'))
-        fragment.add_javascript_url(self.runtime.local_resource_url(self,
-            'public/js/vendor/jquery.html5-placeholder-shim.js'))
-        fragment.add_javascript_url(self.runtime.local_resource_url(self,
-            'public/js/vendor/handlebars-v1.1.2.js'))
-        fragment.add_javascript_url(self.runtime.local_resource_url(self,
-            'public/js/drag_and_drop_edit.js'))
+
+        css_urls = (
+            'public/css/vendor/jquery-ui-1.10.4.custom.min.css',
+            'public/css/drag_and_drop_edit.css'
+        )
+        js_urls = (
+            'public/js/vendor/jquery-ui-1.10.4.custom.min.js',
+            'public/js/vendor/jquery.html5-placeholder-shim.js',
+            'public/js/vendor/handlebars-v1.1.2.js',
+            'public/js/drag_and_drop_edit.js',
+        )
+        for css_url in css_urls:
+            fragment.add_css_url(self.runtime.local_resource_url(self, css_url))
+        for js_url in js_urls:
+            fragment.add_javascript_url(self.runtime.local_resource_url(self, js_url))
 
         fragment.initialize_js('DragAndDropEditBlock')
 
@@ -149,33 +138,12 @@ class DragAndDropBlock(XBlock):
 
     @XBlock.handler
     def get_data(self, request, suffix=''):
-        data = copy.deepcopy(self.data)
-
-        for item in data['items']:
-            # Strip answers
-            del item['feedback']
-            del item['zone']
-            item['inputOptions'] = item.has_key('inputOptions')
-
-        if not self._is_finished():
-            del data['feedback']['finish']
-
-        item_state = self._get_item_state()
-        for item_id, item in item_state.iteritems():
-            definition = next(i for i in self.data['items'] if str(i['id']) == item_id)
-            item['correct_input'] = self._is_correct_input(definition, item.get('input'))
-
-        data['state'] = {
-            'items': item_state,
-            'finished': self._is_finished()
-        }
-
+        data = self._get_data()
         return webob.response.Response(body=json.dumps(data))
 
     @XBlock.json_handler
     def do_attempt(self, attempt, suffix=''):
         item = next(i for i in self.data['items'] if i['id'] == attempt['val'])
-        tot_items = sum(1 for i in self.data['items'] if i['zone'] != 'none')
 
         state = None
         feedback = item['feedback']['incorrect']
@@ -195,7 +163,7 @@ class DragAndDropBlock(XBlock):
                     is_correct = False
         elif item['zone'] == attempt['zone']:
             is_correct_location = True
-            if item.has_key('inputOptions'):
+            if 'inputOptions' in item:
                 # Input value will have to be provided for the item.
                 # It is not (yet) correct and no feedback should be shown yet.
                 is_correct = False
@@ -204,7 +172,11 @@ class DragAndDropBlock(XBlock):
                 # If this item has no input value set, we are done with it.
                 is_correct = True
                 feedback = item['feedback']['correct']
-            state = {'top': attempt['top'], 'left': attempt['left']}
+            state = {
+                'top': attempt['top'],
+                'left': attempt['left'],
+                'absolute': True  # flag for backwards compatibility (values used to be relative)
+            }
 
         if state:
             self.item_state[str(item['id'])] = state
@@ -247,7 +219,34 @@ class DragAndDropBlock(XBlock):
     @XBlock.json_handler
     def reset(self, data, suffix=''):
         self.item_state = {}
-        return {'result':'success'}
+        return self._get_data()
+
+    def _get_data(self):
+        data = copy.deepcopy(self.data)
+
+        for item in data['items']:
+            # Strip answers
+            del item['feedback']
+            del item['zone']
+            item['inputOptions'] = 'inputOptions' in item
+
+        if not self._is_finished():
+            del data['feedback']['finish']
+
+        item_state = self._get_item_state()
+        for item_id, item in item_state.iteritems():
+            definition = next(i for i in self.data['items'] if str(i['id']) == item_id)
+            item['correct_input'] = self._is_correct_input(definition, item.get('input'))
+
+        data['state'] = {
+            'items': item_state,
+            'finished': self._is_finished()
+        }
+
+        data['title'] = self.display_name
+        data['question_text'] = self.question_text
+
+        return data
 
     def _get_item_state(self):
         """
@@ -264,24 +263,6 @@ class DragAndDropBlock(XBlock):
 
         return state
 
-    def _is_correct_input(self, item, val):
-        """
-        Is submitted numerical value within the tolerated margin for this item.
-        """
-        input_options = item.get('inputOptions')
-
-        if input_options:
-            try:
-                submitted_value = float(val)
-            except:
-                return False
-            else:
-                expected_value = input_options['value']
-                margin = input_options['margin']
-                return abs(submitted_value - expected_value) <= margin
-        else:
-            return True
-
     def _get_grade(self):
         """
         Returns the student's grade for this block.
@@ -313,8 +294,8 @@ class DragAndDropBlock(XBlock):
                 total_count += 1
                 item_id = str(item['id'])
                 if item_id in item_state:
-                    if item.has_key('inputOptions'):
-                        if item_state[item_id].has_key('input'):
+                    if 'inputOptions' in item:
+                        if 'input' in item_state[item_id]:
                             completed_count += 1
                     else:
                         completed_count += 1
@@ -325,24 +306,43 @@ class DragAndDropBlock(XBlock):
     def publish_event(self, data, suffix=''):
         try:
             event_type = data.pop('event_type')
-        except KeyError as e:
+        except KeyError:
             return {'result': 'error', 'message': 'Missing event_type in JSON data'}
 
         data['user_id'] = self.scope_ids.user_id
         data['component_id'] = self._get_unique_id()
 
         self.runtime.publish(self, event_type, data)
-        return {'result':'success'}
+        return {'result': 'success'}
 
     def _get_unique_id(self):
         try:
-            unique_id = self.location.name
+            unique_id = self.location.name  # pylint: disable=no-member
         except AttributeError:
             # workaround for xblock workbench
             unique_id = self.parent and self.parent.replace('.',  '-')
         return unique_id
 
     @staticmethod
+    def _is_correct_input(item, val):
+        """
+        Is submitted numerical value within the tolerated margin for this item.
+        """
+        input_options = item.get('inputOptions')
+
+        if input_options:
+            try:
+                submitted_value = float(val)
+            except (ValueError, TypeError):
+                return False
+            else:
+                expected_value = input_options['value']
+                margin = input_options['margin']
+                return abs(submitted_value - expected_value) <= margin
+        else:
+            return True
+
+    @staticmethod
     def workbench_scenarios():
         """
         A canned scenario for display in the workbench.

drag_and_drop_v2/public/css/drag_and_drop.css

@@ -47,15 +47,15 @@
     width: 210px;
     margin: 10px;
     padding: 0 !important; /* LMS tries to override this */
-    font-size: 14px;
     position: relative;
     display: inline;
     float: left;
     list-style-type: none;
 }
 
-.xblock--drag-and-drop .drag-container .items .option {
+.xblock--drag-and-drop .drag-container .option {
     width: 190px;
+    font-size: 14px;
     background: #2e83cd;
     color: #fff;
     position: relative;
@@ -68,28 +68,23 @@
     opacity: 1;
 }
 
-.xblock--drag-and-drop .drag-container .items .option img {
+.xblock--drag-and-drop .drag-container .option img {
     max-width: 100%;
 }
 
-.xblock--drag-and-drop .drag-container .items .option .numerical-input {
-    display: none;
+.xblock--drag-and-drop .drag-container .option .numerical-input {
     height: 32px;
     position: absolute;
     left: calc(100% + 5px);
     top: calc(50% - 16px);
 }
 
-.xblock--drag-and-drop .drag-container .items .option.within-dropzone .numerical-input {
-    display: block;
-}
-
-.xblock--drag-and-drop .drag-container .items .option.within-dropzone .numerical-input .input {
+.xblock--drag-and-drop .drag-container .option .numerical-input .input {
     display: inline-block;
     width: 144px;
 }
 
-.xblock--drag-and-drop .drag-container .items .option.within-dropzone .numerical-input .submit-input {
+.xblock--drag-and-drop .drag-container .option .numerical-input .submit-input {
     box-sizing: border-box;
     position: absolute;
     left: 150px;
@@ -97,22 +92,22 @@
     height: 24px;
 }
 
-.xblock--drag-and-drop .drag-container .items .option.within-dropzone .numerical-input.correct .input-submit,
-.xblock--drag-and-drop .drag-container .items .option.within-dropzone .numerical-input.incorrect .input-submit {
+.xblock--drag-and-drop .drag-container .option .numerical-input.correct .input-submit,
+.xblock--drag-and-drop .drag-container .option .numerical-input.incorrect .input-submit {
     display: none;
 }
 
-.xblock--drag-and-drop .drag-container .items .option.within-dropzone .numerical-input.correct .input {
+.xblock--drag-and-drop .drag-container .option .numerical-input.correct .input {
     background: #ceffce;
     color: #0dad0d;
 }
 
-.xblock--drag-and-drop .drag-container .items .option.within-dropzone .numerical-input.incorrect .input {
+.xblock--drag-and-drop .drag-container .option .numerical-input.incorrect .input {
     background: #ffcece;
     color: #ad0d0d;
 }
 
-.xblock--drag-and-drop .drag-container .items .option.fade {
+.xblock--drag-and-drop .drag-container .option.fade {
     opacity: 0.5;
 }
 
@@ -129,7 +124,6 @@
 }
 
 .xblock--drag-and-drop .target-img {
-    display: none;
     background: url('../img/triangle.png') no-repeat;
     width: 100%;
     height: 100%;
@@ -229,5 +223,4 @@
     float: right;
     color: #3384CA;
     margin-top: 3px;
-    display: none;
 }

drag_and_drop_v2/public/js/drag_and_drop.js

 function DragAndDropBlock(runtime, element) {
-    function publish_event(data) {
-      $.ajax({
-          type: "POST",
-          url: runtime.handlerUrl(element, 'publish_event'),
-          data: JSON.stringify(data)
-      });
-    }
-
-    var dragAndDrop = (function($) {
-        var _fn = {
-            pupup_ts: Date.now(),
-
-            // DOM Elements
-            $ul: $('.xblock--drag-and-drop .items', element),
-            $target: $('.xblock--drag-and-drop .target-img', element),
-            $feedback: $('.xblock--drag-and-drop .feedback .message', element),
-            $popup: $('.xblock--drag-and-drop .popup', element),
-            $reset_button: $('.xblock--drag-and-drop .reset-button', element),
-
-            // Cannot set until items added to DOM
-            $items: {}, // $('.xblock--drag-and-drop .items .option'),
-            $zones: {}, // $('.xblock--drag-and-drop .target .zone'),
-
-            // jQuery UI Draggable options
-            options: {
-                drag: {
+    var root = $(element).find('.xblock--drag-and-drop')[0];
+
+    var __state;
+    var __vdom = virtualDom.h();  // blank virtual DOM
+
+    var init = function() {
+        $.ajax(runtime.handlerUrl(element, 'get_data'), {
+            dataType: 'json'
+        }).done(function(data){
+            setState(data);
+            initDroppable();
+        });
+
+        $(document).on('mousedown touchstart', closePopup);
+        $(element).on('click', '.reset-button', resetExercise);
+        $(element).on('click', '.submit-input', submitInput);
+
+        publishEvent({event_type: 'xblock.drag-and-drop-v2.loaded'});
+    };
+
+    var getState = function() {
+        return __state;
+    };
+
+    var setState = function(new_state) {
+        if (new_state.state.feedback) {
+            if (new_state.state.feedback !== __state.state.feedback) {
+                publishEvent({
+                    event_type: 'xblock.drag-and-drop-v2.feedback.closed',
+                    content: __state.state.feedback,
+                    manually: false
+                });
+            }
+            publishEvent({
+                event_type: 'xblock.drag-and-drop-v2.feedback.opened',
+                content: new_state.state.feedback
+            });
+        }
+        __state = new_state;
+
+        updateDOM(new_state);
+        destroyDraggable();
+        if (!new_state.state.finished) {
+            initDraggable();
+        }
+    };
+
+    var updateDOM = function(state) {
+        var new_vdom = render(state);
+        var patches = virtualDom.diff(__vdom, new_vdom);
+        root = virtualDom.patch(root, patches);
+        __vdom = new_vdom;
+    };
+
+    var publishEvent = function(data) {
+        $.ajax({
+            type: 'POST',
+            url: runtime.handlerUrl(element, 'publish_event'),
+            data: JSON.stringify(data)
+        });
+    };
+
+    var initDroppable = function() {
+        $(root).find('.zone').droppable({
+            accept: '.xblock--drag-and-drop .items .option',
+            tolerance: 'pointer',
+            drop: function(evt, ui) {
+                var item_id = ui.draggable.data('value');
+                var zone = $(this).data('zone');
+                var position = ui.draggable.position();
+                var top = position.top + 'px';
+                var left = position.left + 'px';
+                var state = getState();
+                state.state.items[item_id] = {
+                    top: top,
+                    left: left,
+                    absolute: true,
+                    submitting_location: true
+                };
+                // Wrap in setTimeout to let the droppable event finish.
+                setTimeout(function() {
+                    setState(state);
+                    submitLocation(item_id, zone, top, left);
+                }, 0);
+            }
+        });
+    };
+
+    var initDraggable = function() {
+        $(root).find('.items .option').not('[data-drag-disabled=true]').each(function() {
+            try {
+                $(this).draggable({
                     containment: '.xblock--drag-and-drop .drag-container',
                     cursor: 'move',
-                    stack: '.xblock--drag-and-drop .items .option'
-                },
-                drop: {
-                    accept: '.xblock--drag-and-drop .items .option',
-                    tolerance: 'pointer'
-                }
-            },
-
-            tpl: {
-                init: function() {
-                    _fn.tpl = {
-                        item: Handlebars.compile($("#item-tpl", element).html()),
-                        imageItem: Handlebars.compile($("#image-item-tpl", element).html()),
-                        zoneElement: Handlebars.compile($("#zone-element-tpl", element).html())
-                    };
-                }
-            },
-
-            init: function(data) {
-                _fn.data = data;
-
-                // Compile templates
-                _fn.tpl.init();
-
-                // Add the items to the page
-                _fn.items.draw();
-                _fn.zones.draw();
-
-                // Init drag and drop plugin
-                _fn.$items.draggable(_fn.options.drag);
-                _fn.$zones.droppable(_fn.options.drop);
-
-                // Init click handlers
-                _fn.eventHandlers.init(_fn.$items, _fn.$zones);
-
-                // Position the already correct items
-                _fn.items.init();
-
-                // Load welcome or final feedback
-                if (_fn.data.state.finished)
-                    _fn.finish(_fn.data.feedback.finish);
-                else
-                    _fn.feedback.set(_fn.data.feedback.start);
-
-                // Set the target image
-                if (_fn.data.targetImg)
-                    _fn.$target.css('background', 'url(' + _fn.data.targetImg + ') no-repeat');
-
-                // Display target image
-                _fn.$target.show();
-
-                // Display the zone names if required
-                if (_fn.data.displayLabels) {
-                    $('p', _fn.$zones).css('visibility', 'visible');
-                }
-            },
-
-            finish: function(final_feedback) {
-                // Disable any decoy items
-                _fn.$items.draggable('disable');
-                _fn.$reset_button.show();
-
-                // Show final feedback
-                if (final_feedback) _fn.feedback.set(final_feedback);
-            },
-
-            reset: function() {
-                _fn.$items.draggable('enable');
-                _fn.$items.find('.numerical-input').removeClass('correct incorrect');
-                _fn.$items.find('.numerical-input .input').prop('disabled', false).val('');
-                _fn.$items.find('.numerical-input .submit-input').prop('disabled', false);
-                _fn.$items.each(function(index, element) {
-                    _fn.eventHandlers.drag.reset($(element));
-                });
-                _fn.$popup.hide();
-                _fn.$reset_button.hide();
-                _fn.feedback.set(_fn.data.feedback.start);
-            },
-
-            eventHandlers: {
-                init: function($drag, $dropzone) {
-                    var handlers = _fn.eventHandlers;
-
-                    $drag.on('dragstart', handlers.drag.start);
-                    $drag.on('dragstop', handlers.drag.stop);
-
-                    $dropzone.on('drop', handlers.drop.success);
-                    $dropzone.on('dropover', handlers.drop.hover);
-
-                    $(element).on('click', '.submit-input', handlers.drag.submitInput);
-
-                    $(document).on('click', function(evt) {
-                        // Click should only close the popup if the popup has been
-                        // visible for at least one second.
-                        var popup_timeout = 1000;
-                        if (Date.now() - _fn.popup_ts > popup_timeout) {
-                            handlers.popup.close(evt);
-                        }
-                    });
-                    _fn.$reset_button.on('click', handlers.problem.reset);
-                },
-                problem: {
-                    reset: function(event, ui) {
-                        $.ajax({
-                            type: "POST",
-                            url: runtime.handlerUrl(element, "reset"),
-                            data: "{}",
-                            success: _fn.reset
-                        });
-                    }
-                },
-                popup: {
-                    close: function(event, ui) {
-                        target = $(event.target);
-                        popup_box = ".xblock--drag-and-drop .popup";
-                        close_button = ".xblock--drag-and-drop .popup .close";
-                        if (target.is(popup_box)) {
-                            return;
-                        };
-                        if (target.parents(popup_box).length>0 && !target.is(close_button)) {
-                            return;
-                        };
-
-                        _fn.$popup.hide();
-                        publish_event({
-                            event_type: 'xblock.drag-and-drop-v2.feedback.closed',
-                            content: _fn.$popup.find(".popup-content").text(),
-                            manually: true
-                        });
-                    }
-                },
-                drag: {
-                    start: function(event, ui) {
-                        _fn.eventHandlers.popup.close(event, ui);
-
-                        target = $(event.currentTarget);
-                        target.removeClass('within-dropzone fade');
-
-                        var item_id = target.data("value");
-                        publish_event({event_type:'xblock.drag-and-drop-v2.item.picked-up', item_id:item_id});
-                    },
-
-                    stop: function(event, ui) {
-                        var $el = $(event.currentTarget);
-
-                        if (!$el.hasClass('within-dropzone')) {
-                            // Return to original position
-                            _fn.eventHandlers.drag.reset($el);
-                        } else {
-                            _fn.eventHandlers.drag.submitLocation($el);
-                        }
-                    },
-
-                    submitLocation: function($el) {
-                        var val = $el.data('value'),
-                            zone = $el.data('zone') || null;
-
-                        $.post(runtime.handlerUrl(element, 'do_attempt'),
-                            JSON.stringify({
-                                val: val,
-                                zone: zone,
-                                top: $el.css('top'),
-                                left: $el.css('left')
-                        }), 'json').done(function(data){
-                            if (data.correct_location) {
-                                $el.draggable('disable');
-
-                                if (data.finished) {
-                                    _fn.finish(data.final_feedback);
-                                }
-                            } else {
-                                // Return to original position
-                                _fn.eventHandlers.drag.reset($el);
-                            }
-
-                            if (data.feedback) {
-                                _fn.feedback.popup(data.feedback, data.correct);
-                            }
+                    stack: '.xblock--drag-and-drop .items .option',
+                    revert: 'invalid',
+                    revertDuration: 150,
+                    start: function(evt, ui) {
+                        var item_id = $(this).data('value');
+                        publishEvent({
+                            event_type: 'xblock.drag-and-drop-v2.item.picked-up',
+                            item_id: item_id
                         });
-                    },
-
-                    submitInput: function(evt) {
-                        var $el = $(this).closest('li.option');
-                        var $input_div = $el.find('.numerical-input');
-                        var $input = $input_div.find('.input');
-                        var val = $el.data('value');
-
-                        if (!$input.val()) {
-                            // Don't submit if the user didn't enter anything yet.
-                            return;
-                        }
-
-                        $input.prop('disabled', true);
-                        $input_div.find('.submit-input').prop('disabled', true);
-
-                        $.post(runtime.handlerUrl(element, 'do_attempt'),
-                            JSON.stringify({
-                                val: val,
-                                input: $input.val()
-                        }), 'json').done(function(data){
-                            if (data.correct) {
-                                $input_div.removeClass('incorrect').addClass('correct');
-                            } else {
-                                $input_div.removeClass('correct').addClass('incorrect');
-                            }
-
-                            if (data.finished) {
-                                _fn.finish(data.final_feedback);
-                            }
-
-                            if (data.feedback) {
-                                _fn.feedback.popup(data.feedback, data.correct);
-                            }
-                        });
-                    },
-
-                    set: function($el, top, left) {
-                        $el.addClass('within-dropzone')
-                            .css({
-                                top: top,
-                                left: left
-                            })
-                            .draggable('disable');
-                    },
-
-                    reset: function($el) {
-                        $el.removeClass('within-dropzone fade')
-                            .css({
-                                top: '',
-                                left: ''
-                            });
                     }
-                },
-                drop: {
-                    hover: function(event, ui) {
-                        var zone = $(event.currentTarget).data('zone');
-                        ui.draggable.data('zone', zone);
-                    },
-                    success: function(event, ui) {
-                        ui.draggable.addClass('within-dropzone');
-                        var item = _fn.data.items[ui.draggable.data('value')];
-                        if (item.inputOptions) {
-                            ui.draggable.find('.input').focus();
-                        }
-                    }
-                }
-            },
-
-            items: {
-                init: function() {
-                    _fn.$items.each(function (){
-                        var $el = $(this),
-                            saved_entry = _fn.data.state.items[$el.data('value')];
-                        if (saved_entry) {
-                            var $input_div = $el.find('.numerical-input')
-                            var $input = $input_div.find('.input');
-                            $input.val(saved_entry.input);
-                          console.log('wuwuwu', saved_entry)
-                            if ('input' in saved_entry) {
-                                $input_div.addClass(saved_entry.correct_input ? 'correct' : 'incorrect');
-                                $input.prop('disabled', true);
-                                $input_div.find('.submit-input').prop('disabled', true);
-                            }
-                            if ('input' in saved_entry || saved_entry.correct_input) {
-                                $el.addClass('fade');
-                            }
-                            _fn.eventHandlers.drag.set($el, saved_entry.top, saved_entry.left);
-                        }
-                    });
-                },
-                draw: function() {
-                    var list = [],
-                        items = _fn.data.items,
-                        tpl = _fn.tpl.item,
-                        img_tpl = _fn.tpl.imageItem;
-
-                    items.forEach(function(item) {
-                        if (item.backgroundImage.length > 0) {
-                            list.push(img_tpl(item));
-                        } else {
-                            list.push(tpl(item));
-                        }
-                    });
-
-                    // Update DOM
-                    _fn.$ul.html(list.join(''));
-
-                    // Set variable
-                    _fn.$items = $('.xblock--drag-and-drop .items .option', element);
-                }
-            },
-
-            zones: {
-                draw: function() {
-                    var html = [],
-                        zones = _fn.data.zones,
-                        tpl = _fn.tpl.zoneElement,
-                        i,
-                        len = zones.length;
-
-                    for (i=0; i<len; i++) {
-                        html.push(tpl(zones[i]));
-                    }
-
-                    // Update DOM
-                    _fn.$target.html(html.join(''));
-
-                    // Set variable
-                    _fn.$zones = _fn.$target.find('.zone');
-                }
-            },
-
-            feedback: {
-                // Update DOM with feedback
-                set: function(str) {
-                    if ($.trim(str) === '') _fn.$feedback.parent().hide();
-                    else _fn.$feedback.parent().show();
-                    return _fn.$feedback.html(str);
-                },
-
-                // Show a feedback popup
-                popup: function(str, boo) {
-                    if (str === undefined || str === '') return;
-
-                    if (_fn.$popup.is(":visible")) {
-                        publish_event({
-                            event_type: "xblock.drag-and-drop-v2.feedback.closed",
-                            content: _fn.$popup.find(".popup-content").text(),
-                            manually: false
-                        });
-                    }
-                    publish_event({
-                        event_type: "xblock.drag-and-drop-v2.feedback.opened",
-                        content: str
-                    });
-
-                    _fn.$popup.find(".popup-content").html(str);
-                    _fn.$popup.show();
-
-                    _fn.popup_ts = Date.now();
+                });
+            } catch (e) {
+                // Initializing the draggable will fail if draggable was already
+                // initialized. That's expected, ignore the exception.
+            }
+        });
+    };
+
+    var destroyDraggable = function() {
+        $(root).find('.items .option[data-drag-disabled=true]').each(function() {
+            try {
+                $(this).draggable('destroy');
+            } catch (e) {
+                // Destroying the draggable will fail if draggable was
+                // not initialized in the first place. Ignore the exception.
+            }
+        });
+    };
+
+    var submitLocation = function(item_id, zone, top, left) {
+        if (!zone) {
+            return;
+        }
+        var url = runtime.handlerUrl(element, 'do_attempt');
+        var data = {val: item_id, zone: zone, top: top, left: left};
+        $.post(url, JSON.stringify(data), 'json').done(function(data){
+            var state = getState();
+            if (data.correct_location) {
+                state.state.items[item_id].correct_input = Boolean(data.correct);
+                state.state.items[item_id].submitting_location = false;
+            } else {
+                delete state.state.items[item_id];
+            }
+            state.state.feedback = data.feedback;
+            if (data.finished) {
+                state.state.finished = true;
+                state.feedback.finish = data.final_feedback;
+            }
+            setState(state);
+        });
+    };
+
+    var submitInput = function(evt) {
+        var item = $(evt.target).closest('.option');
+        var input_div = item.find('.numerical-input');
+        var input = input_div.find('.input');
+        var input_value = input.val();
+        var item_id = item.data('value');
+
+        if (!input_value) {
+            // Don't submit if the user didn't enter anything yet.
+            return;
+        }
+
+        var state = getState();
+        state.state.items[item_id].input = input_value;
+        state.state.items[item_id].submitting_input = true;
+        setState(state);
+
+        var url = runtime.handlerUrl(element, 'do_attempt');
+        var data = {val: item_id, input: input_value};
+        $.post(url, JSON.stringify(data), 'json').done(function(data) {
+            state.state.items[item_id].submitting_input = false;
+            state.state.items[item_id].correct_input = data.correct;
+            state.state.feedback = data.feedback;
+            if (data.finished) {
+                state.state.finished = true;
+                state.feedback.finish = data.final_feedback;
+            }
+            setState(state);
+        });
+    };
+
+    var closePopup = function(evt) {
+        var target = $(evt.target);
+        var popup_box = '.xblock--drag-and-drop .popup';
+        var close_button = '.xblock--drag-and-drop .popup .close';
+        var submit_input_button = '.xblock--drag-and-drop .submit-input';
+        var state = getState();
+
+        if (!state.state.feedback) {
+            return;
+        }
+        if (target.is(popup_box) || target.is(submit_input_button)) {
+            return;
+        }
+        if (target.parents(popup_box).length && !target.is(close_button)) {
+            return;
+        }
+
+        publishEvent({
+            event_type: 'xblock.drag-and-drop-v2.feedback.closed',
+            content: state.state.feedback,
+            manually: true
+        });
+
+        delete state.state.feedback;
+        setState(state);
+    };
+
+    var resetExercise = function() {
+        $.ajax({
+            type: 'POST',
+            url: runtime.handlerUrl(element, 'reset'),
+            data: '{}',
+            success: setState
+        });
+    };
+
+    var render = function(state) {
+        var items = state.items.map(function(item) {
+            var item_state = state.state.items[item.id];
+            var position = item_state || {};
+            var input = null;
+            if (item.inputOptions) {
+                input = {
+                    is_visible: item_state && !item_state.submitting_location,
+                    has_value: Boolean(item_state && 'input' in item_state),
+                    value : (item_state && item_state.input) || '',
+                    class_name: undefined,
+                };
+                if (input.has_value && !item_state.submitting_input) {
+                    input.class_name = item_state.correct_input ? 'correct' : 'incorrect';
                 }
-            },
-
-            data: null
-        };
-
-        return {
-            init: _fn.init,
+            }
+            return {
+                value: item.id,
+                drag_disabled: Boolean(item_state || state.state.finished),
+                width: item.size.width,
+                height: item.size.height,
+                top: position.top,
+                left: position.left,
+                position: position.absolute ? 'absolute' : 'relative',
+                class_name: item_state && ('input' in item_state || item_state.correct_input) ? 'fade': undefined,
+                input: input,
+                content_html: item.backgroundImage ? '<img src="' + item.backgroundImage + '"/>' : item.displayName
+            };
+        });
+
+        var context = {
+            header_html: state.title,
+            question_html: state.question_text,
+            popup_html: state.state.feedback || '',
+            feedback_html: $.trim(state.state.finished ? state.feedback.finish : state.feedback.start),
+            target_img_src: state.targetImg,
+            display_zone_labels: state.displayLabels,
+            display_reset_button: state.state.finished,
+            zones: state.zones,
+            items: items
         };
-    })(jQuery);
 
-    $.ajax(runtime.handlerUrl(element, 'get_data'), {
-        dataType: 'json'
-    }).done(function(data){
-        dragAndDrop.init(data);
-    });
+        return DragAndDropBlock.renderView(context);
+    };
 
-    publish_event({event_type:"xblock.drag-and-drop-v2.loaded"});
+    init();
 }

drag_and_drop_v2/public/js/vendor/virtual-dom-1.3.0.min.js

+!function(e){if("object"==typeof exports&&"undefined"!=typeof module)module.exports=e();else if("function"==typeof define&&define.amd)define("virtual-dom-1.3.0",[],e);else{var n;"undefined"!=typeof window?n=window:"undefined"!=typeof global?n=global:"undefined"!=typeof self&&(n=self),n.virtualDom=e()}}(function(){return function e(n,t,r){function o(s,u){if(!t[s]){if(!n[s]){var a="function"==typeof require&&require;if(!u&&a)return a(s,!0);if(i)return i(s,!0);var f=new Error("Cannot find module '"+s+"'");throw f.code="MODULE_NOT_FOUND",f}var v=t[s]={exports:{}};n[s][0].call(v.exports,function(e){var t=n[s][1][e];return o(t?t:e)},v,v.exports,e,n,t,r)}return t[s].exports}for(var i="function"==typeof require&&require,s=0;s<r.length;s++)o(r[s]);return o}({1:[function(e,n){var t=e("./vdom/create-element.js");n.exports=t},{"./vdom/create-element.js":15}],2:[function(e,n){var t=e("./vtree/diff.js");n.exports=t},{"./vtree/diff.js":35}],3:[function(e,n){var t=e("./virtual-hyperscript/index.js");n.exports=t},{"./virtual-hyperscript/index.js":22}],4:[function(e,n){var t=e("./diff.js"),r=e("./patch.js"),o=e("./h.js"),i=e("./create-element.js");n.exports={diff:t,patch:r,h:o,create:i}},{"./create-element.js":1,"./diff.js":2,"./h.js":3,"./patch.js":13}],5:[function(e,n){n.exports=function(e){var n,t=String.prototype.split,r=/()??/.exec("")[1]===e;return n=function(n,o,i){if("[object RegExp]"!==Object.prototype.toString.call(o))return t.call(n,o,i);var s,u,a,f,v=[],d=(o.ignoreCase?"i":"")+(o.multiline?"m":"")+(o.extended?"x":"")+(o.sticky?"y":""),c=0,o=new RegExp(o.source,d+"g");for(n+="",r||(s=new RegExp("^"+o.source+"$(?!\\s)",d)),i=i===e?-1>>>0:i>>>0;(u=o.exec(n))&&(a=u.index+u[0].length,!(a>c&&(v.push(n.slice(c,u.index)),!r&&u.length>1&&u[0].replace(s,function(){for(var n=1;n<arguments.length-2;n++)arguments[n]===e&&(u[n]=e)}),u.length>1&&u.index<n.length&&Array.prototype.push.apply(v,u.slice(1)),f=u[0].length,c=a,v.length>=i)));)o.lastIndex===u.index&&o.lastIndex++;return c===n.length?(f||!o.test(""))&&v.push(""):v.push(n.slice(c)),v.length>i?v.slice(0,i):v}}()},{}],6:[function(){},{}],7:[function(e,n){"use strict";function t(e){var n=e[i];return n||(n=e[i]={}),n}var r=e("individual/one-version"),o="7";r("ev-store",o);var i="__EV_STORE_KEY@"+o;n.exports=t},{"individual/one-version":9}],8:[function(e,n){(function(e){"use strict";function t(e,n){return e in r?r[e]:(r[e]=n,n)}var r="undefined"!=typeof window?window:"undefined"!=typeof e?e:{};n.exports=t}).call(this,"undefined"!=typeof global?global:"undefined"!=typeof self?self:"undefined"!=typeof window?window:{})},{}],9:[function(e,n){"use strict";function t(e,n,t){var o="__INDIVIDUAL_ONE_VERSION_"+e,i=o+"_ENFORCE_SINGLETON",s=r(i,n);if(s!==n)throw new Error("Can only have one copy of "+e+".\nYou already have version "+s+" installed.\nThis means you cannot install version "+n);return r(o,t)}var r=e("./index.js");n.exports=t},{"./index.js":8}],10:[function(e,n){(function(t){var r="undefined"!=typeof t?t:"undefined"!=typeof window?window:{},o=e("min-document");if("undefined"!=typeof document)n.exports=document;else{var i=r["__GLOBAL_DOCUMENT_CACHE@4"];i||(i=r["__GLOBAL_DOCUMENT_CACHE@4"]=o),n.exports=i}}).call(this,"undefined"!=typeof global?global:"undefined"!=typeof self?self:"undefined"!=typeof window?window:{})},{"min-document":6}],11:[function(e,n){"use strict";n.exports=function(e){return"object"==typeof e&&null!==e}},{}],12:[function(e,n){function t(e){return"[object Array]"===o.call(e)}var r=Array.isArray,o=Object.prototype.toString;n.exports=r||t},{}],13:[function(e,n){var t=e("./vdom/patch.js");n.exports=t},{"./vdom/patch.js":18}],14:[function(e,n){function t(e,n,t){for(var i in n){var a=n[i];void 0===a?r(e,i,a,t):u(a)?(r(e,i,a,t),a.hook&&a.hook(e,i,t?t[i]:void 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d=null===e.namespace?f.createElement(e.tagName):f.createElementNS(e.namespace,e.tagName),c=e.properties;o(d,c);for(var p=e.children,l=0;l<p.length;l++){var h=t(p[l],n);h&&d.appendChild(h)}return d}var r=e("global/document"),o=e("./apply-properties"),i=e("../vnode/is-vnode.js"),s=e("../vnode/is-vtext.js"),u=e("../vnode/is-widget.js"),a=e("../vnode/handle-thunk.js");n.exports=t},{"../vnode/handle-thunk.js":24,"../vnode/is-vnode.js":27,"../vnode/is-vtext.js":28,"../vnode/is-widget.js":29,"./apply-properties":14,"global/document":10}],16:[function(e,n){function t(e,n,t,o){return t&&0!==t.length?(t.sort(i),r(e,n,t,o,0)):{}}function r(e,n,t,i,u){if(i=i||{},e){o(t,u,u)&&(i[u]=e);var a=n.children;if(a)for(var f=e.childNodes,v=0;v<n.children.length;v++){u+=1;var d=a[v]||s,c=u+(d.count||0);o(t,u,c)&&r(f[v],d,t,i,u),u=c}}return i}function o(e,n,t){if(0===e.length)return!1;for(var r,o,i=0,s=e.length-1;s>=i;){if(r=(s+i)/2>>0,o=e[r],i===s)return 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t=!n.hasOwnProperty("id"),s=r(e,o),u=null;i.test(s[1])&&(u="DIV");var a,f,v,d;for(d=0;d<s.length;d++)f=s[d],f&&(v=f.charAt(0),u?"."===v?(a=a||[],a.push(f.substring(1,f.length))):"#"===v&&t&&(n.id=f.substring(1,f.length)):u=f);return a&&(n.className&&a.push(n.className),n.className=a.join(" ")),n.namespace?u:u.toUpperCase()}var r=e("browser-split"),o=/([\.#]?[a-zA-Z0-9_:-]+)/,i=/^\.|#/;n.exports=t},{"browser-split":5}],24:[function(e,n){function t(e,n){var t=e,o=n;return u(n)&&(o=r(n,e)),u(e)&&(t=r(e,null)),{a:t,b:o}}function r(e,n){var t=e.vnode;if(t||(t=e.vnode=e.render(n)),!(o(t)||i(t)||s(t)))throw new Error("thunk did not return a valid node");return t}var o=e("./is-vnode"),i=e("./is-vtext"),s=e("./is-widget"),u=e("./is-thunk");n.exports=t},{"./is-thunk":25,"./is-vnode":27,"./is-vtext":28,"./is-widget":29}],25:[function(e,n){function t(e){return e&&"Thunk"===e.type}n.exports=t},{}],26:[function(e,n){function t(e){return e&&("function"==typeof e.hook&&!e.hasOwnProperty("hook")||"function"==typeof e.unhook&&!e.hasOwnProperty("unhook"))}n.exports=t},{}],27:[function(e,n){function t(e){return e&&"VirtualNode"===e.type&&e.version===r}var r=e("./version");n.exports=t},{"./version":30}],28:[function(e,n){function t(e){return e&&"VirtualText"===e.type&&e.version===r}var r=e("./version");n.exports=t},{"./version":30}],29:[function(e,n){function t(e){return e&&"Widget"===e.type}n.exports=t},{}],30:[function(e,n){n.exports="1"},{}],31:[function(e,n){function t(e,n,t,r,v){this.tagName=e,this.properties=n||a,this.children=t||f,this.key=null!=r?String(r):void 0,this.namespace="string"==typeof v?v:null;var d,c=t&&t.length||0,p=0,l=!1,h=!1,y=!1;for(var g in n)if(n.hasOwnProperty(g)){var x=n[g];u(x)&&x.unhook&&(d||(d={}),d[g]=x)}for(var w=0;c>w;w++){var m=t[w];o(m)?(p+=m.count||0,!l&&m.hasWidgets&&(l=!0),!h&&m.hasThunks&&(h=!0),y||!m.hooks&&!m.descendantHooks||(y=!0)):!l&&i(m)?"function"==typeof m.destroy&&(l=!0):!h&&s(m)&&(h=!0)}this.count=c+p,this.hasWidgets=l,this.hasThunks=h,this.hooks=d,this.descendantHooks=y}var r=e("./version"),o=e("./is-vnode"),i=e("./is-widget"),s=e("./is-thunk"),u=e("./is-vhook");n.exports=t;var a={},f=[];t.prototype.version=r,t.prototype.type="VirtualNode"},{"./is-thunk":25,"./is-vhook":26,"./is-vnode":27,"./is-widget":29,"./version":30}],32:[function(e,n){function t(e,n,t){this.type=Number(e),this.vNode=n,this.patch=t}var r=e("./version");t.NONE=0,t.VTEXT=1,t.VNODE=2,t.WIDGET=3,t.PROPS=4,t.ORDER=5,t.INSERT=6,t.REMOVE=7,t.THUNK=8,n.exports=t,t.prototype.version=r,t.prototype.type="VirtualPatch"},{"./version":30}],33:[function(e,n){function t(e){this.text=String(e)}var r=e("./version");n.exports=t,t.prototype.version=r,t.prototype.type="VirtualText"},{"./version":30}],34:[function(e,n){function t(e,n){var s;for(var u in e){u in n||(s=s||{},s[u]=void 0);var a=e[u],f=n[u];if(a!==f)if(o(a)&&o(f))if(r(f)!==r(a))s=s||{},s[u]=f;else if(i(f))s=s||{},s[u]=f;else{var v=t(a,f);v&&(s=s||{},s[u]=v)}else s=s||{},s[u]=f}for(var d in n)d in e||(s=s||{},s[d]=n[d]);return s}function r(e){return Object.getPrototypeOf?Object.getPrototypeOf(e):e.__proto__?e.__proto__:e.constructor?e.constructor.prototype:void 0}var o=e("is-object"),i=e("../vnode/is-vhook");n.exports=t},{"../vnode/is-vhook":26,"is-object":11}],35:[function(e,n){function t(e,n){var t={a:e};return r(e,n,t,0),t}function r(e,n,t,r){if(e!==n){var s=t[r],a=!1;if(w(e)||w(n))u(e,n,t,r);else if(null==n)x(e)||(i(e,t,r),s=t[r]),s=p(s,new h(h.REMOVE,e,n));else if(y(n))if(y(e))if(e.tagName===n.tagName&&e.namespace===n.namespace&&e.key===n.key){var f=j(e.properties,n.properties);f&&(s=p(s,new h(h.PROPS,e,f))),s=o(e,n,t,s,r)}else s=p(s,new h(h.VNODE,e,n)),a=!0;else s=p(s,new h(h.VNODE,e,n)),a=!0;else g(n)?g(e)?e.text!==n.text&&(s=p(s,new h(h.VTEXT,e,n))):(s=p(s,new h(h.VTEXT,e,n)),a=!0):x(n)&&(x(e)||(a=!0),s=p(s,new h(h.WIDGET,e,n)));s&&(t[r]=s),a&&i(e,t,r)}}function o(e,n,t,o,i){for(var s=e.children,u=d(s,n.children),a=s.length,f=u.length,v=a>f?a:f,c=0;v>c;c++){var l=s[c],g=u[c];i+=1,l?r(l,g,t,i):g&&(o=p(o,new h(h.INSERT,null,g))),y(l)&&l.count&&(i+=l.count)}return u.moves&&(o=p(o,new h(h.ORDER,e,u.moves))),o}function i(e,n,t){f(e,n,t),s(e,n,t)}function s(e,n,t){if(x(e))"function"==typeof e.destroy&&(n[t]=p(n[t],new h(h.REMOVE,e,null)));else if(y(e)&&(e.hasWidgets||e.hasThunks))for(var r=e.children,o=r.length,i=0;o>i;i++){var a=r[i];t+=1,s(a,n,t),y(a)&&a.count&&(t+=a.count)}else w(e)&&u(e,null,n,t)}function u(e,n,r,o){var i=m(e,n),s=t(i.a,i.b);a(s)&&(r[o]=new h(h.THUNK,null,s))}function a(e){for(var n in e)if("a"!==n)return!0;return!1}function f(e,n,t){if(y(e)){if(e.hooks&&(n[t]=p(n[t],new h(h.PROPS,e,v(e.hooks)))),e.descendantHooks||e.hasThunks)for(var r=e.children,o=r.length,i=0;o>i;i++){var s=r[i];t+=1,f(s,n,t),y(s)&&s.count&&(t+=s.count)}}else w(e)&&u(e,null,n,t)}function v(e){var n={};for(var t in e)n[t]=void 0;return n}function d(e,n){var t=c(n);if(!t)return n;var r=c(e);if(!r)return n;var o={},i={};for(var s in t)o[t[s]]=r[s];for(var u in r)i[r[u]]=t[u];for(var a=e.length,f=n.length,v=a>f?a:f,d=[],p=0,l=0,h=0,y={},g=y.removes={},x=y.reverse={},w=!1;v>p;){var m=i[l];if(void 0!==m)d[l]=n[m],m!==h&&(y[m]=h,x[h]=m,w=!0),h++;else if(l in i)d[l]=void 0,g[l]=h++,w=!0;else{for(;void 0!==o[p];)p++;if(v>p){var j=n[p];j&&(d[l]=j,p!==h&&(w=!0,y[p]=h,x[h]=p),h++),p++}}l++}return w&&(d.moves=y),d}function c(e){var n,t;for(n=0;n<e.length;n++){var r=e[n];void 0!==r.key&&(t=t||{},t[r.key]=n)}return t}function p(e,n){return e?(l(e)?e.push(n):e=[e,n],e):n}var l=e("x-is-array"),h=e("../vnode/vpatch"),y=e("../vnode/is-vnode"),g=e("../vnode/is-vtext"),x=e("../vnode/is-widget"),w=e("../vnode/is-thunk"),m=e("../vnode/handle-thunk"),j=e("./diff-props");n.exports=t},{"../vnode/handle-thunk":24,"../vnode/is-thunk":25,"../vnode/is-vnode":27,"../vnode/is-vtext":28,"../vnode/is-widget":29,"../vnode/vpatch":32,"./diff-props":34,"x-is-array":12}]},{},[4])(4)});
+
+if (window.require && !window.virtualDom) {
+  require(['virtual-dom-1.3.0'], function(virtualDom) { window.virtualDom = virtualDom; });
+}

drag_and_drop_v2/public/js/view.js

+(function(h) {
+
+    var FocusHook = function() {
+        if (!(this instanceof FocusHook)) {
+            return new FocusHook();
+        }
+    };
+
+    FocusHook.prototype.hook = function(node, prop, prev) {
+        setTimeout(function() {
+            if (document.activeElement !== node) {
+                node.focus();
+            }
+        }, 0);
+    };
+
+    var px = function(n) {
+        return n + 'px';
+    };
+
+    var renderCollection = function(template, collection, ctx) {
+        return collection.map(function(item) {
+            return template(item, ctx);
+        });
+    };
+
+    var itemInputTemplate = function(input) {
+        if (!input) {
+            return null;
+        }
+        var focus_hook = input.has_value ? undefined : FocusHook();
+        return (
+            h('div.numerical-input', {className: input.class_name,
+                                      style: {display: input.is_visible ? 'block' : 'none'}}, [
+                h('input.input', {type: 'text', value: input.value, disabled: input.has_value,
+                                  focusHook: focus_hook}),
+                h('button.submit-input', {disabled: input.has_value}, 'ok')
+            ])
+        );
+    };
+
+    var itemTemplate = function(item) {
+        return (
+            h('div.option', {className: item.class_name,
+                             attributes: {'data-value': item.value, 'data-drag-disabled': item.drag_disabled},
+                             style: {width: item.width, height: item.height,
+                                     top: item.top, left: item.left, position: item.position}}, [
+                h('div', {innerHTML: item.content_html}),
+                itemInputTemplate(item.input)
+            ])
+        );
+    };
+
+    var zoneTemplate = function(zone, ctx) {
+        return (
+            h('div.zone', {id: zone.id, attributes: {'data-zone': zone.title},
+                           style: {top: px(zone.y), left: px(zone.x),
+                                   width: px(zone.width), height: px(zone.height)}},
+              h('p', {style: {visibility: ctx.display_zone_labels ? 'visible': 'hidden'}}, zone.title))
+        );
+    };
+
+    var feedbackTemplate = function(ctx) {
+        var feedback_display = ctx.feedback_html ? 'block' : 'none';
+        var reset_button_display = ctx.display_reset_button ? 'block' : 'none';
+        return (
+            h('section.feedback', [
+                h('div.reset-button', {style: {display: reset_button_display}}, 'Reset exercise'),
+                h('div.title1', {style: {display: feedback_display}}, 'Feedback'),
+                h('p.message', {style: {display: feedback_display},
+                                innerHTML: ctx.feedback_html})
+            ])
+        );
+    };
+
+    var mainTemplate = function(ctx) {
+        return (
+            h('section.xblock--drag-and-drop', [
+                h('h2.problem-header', {innerHTML: ctx.header_html}),
+                h('section.problem', {role: 'application'}, [
+                    h('div.title1', 'Question'),
+                    h('p', {innerHTML: ctx.question_html})
+                ]),
+                h('section.drag-container', [
+                    h('div.items', renderCollection(itemTemplate, ctx.items, ctx)),
+                    h('div.target', [
+                        h('div.popup', {style: {display: ctx.popup_html ? 'block' : 'none'}}, [
+                            h('div.close.icon-remove-sign.fa-times-circle'),
+                            h('p.popup-content', {innerHTML: ctx.popup_html})
+                        ]),
+                        h('div.target-img', {style: {backgroundImage: ctx.target_img_src}},
+                          renderCollection(zoneTemplate, ctx.zones, ctx))
+                    ]),
+                    h('div.clear')
+                ]),
+                feedbackTemplate(ctx)
+            ])
+        );
+    };
+
+    DragAndDropBlock.renderView = mainTemplate;
+
+})(virtualDom.h);

drag_and_drop_v2/templates/html/drag_and_drop.html

-<section class="xblock--drag-and-drop">
-    {{ js_templates|safe }}
-
-    <h2 class="problem-header">
-      {{ title|safe }}
-    </h2>
-
-    <section class="problem" role="application">
-        <div class="title1">Question</div>
-        <p>{{ question_text|safe }}</p>
-    </section>
-
-    <section class="drag-container">
-        <ul class="items"></ul>
-
-        <div class="target">
-            <div class="popup">
-                <div class="close icon-remove-sign fa-times-circle"></div>
-                <p class="popup-content"></p>
-            </div>
-            <div class="target-img"></div>
-        </div>
-
-        <div class="clear"></div>
-    </section>
-
-
-    <section class="feedback">
-        <div class="reset-button">Reset exercise</div>
-        <div class="title1">Feedback</div>
-        <p class="message"></p>
-    </section>
-</section>
+<section class="xblock--drag-and-drop"></section>

drag_and_drop_v2/templates/html/js_templates.html

-<script id="item-tpl" type="text/html">
-    <li class="option" data-value="{{ id }}"
-        style="width: {{ size.width }}; height: {{ size.height }}">
-        {{{ displayName }}}
-        {{#if inputOptions}}
-          <div class="numerical-input">
-            <input class="input" type="text" />
-            <button class="submit-input">ok</button>
-          </div>
-        {{/if}}
-    </li>
-</script>
-
-<script id="image-item-tpl" type="text/html">
-    <li class="option" data-value="{{ id }}"
-        style="width: {{ size.width }}; height: {{ size.height }}">
-        <img src="{{ backgroundImage }}" />
-        {{#if inputOptions}}
-          <input class="input" type="text" />
-          <button class="submit-input">ok</button>
-        {{/if}}
-    </li>
-</script>
-
 <script id="zone-element-tpl" type="text/html">
     <div id="{{ id }}" class="zone" data-zone="{{ title }}" style="
         top:{{ y }}px;

drag_and_drop_v2/utils.py

@@ -3,17 +3,11 @@
 
 # Imports ###########################################################
 
-import logging
 import pkg_resources
 
 from django.template import Context, Template
 
 
-# Globals ###########################################################
-
-log = logging.getLogger(__name__)
-
-
 # Functions #########################################################
 
 def load_resource(resource_path):
@@ -23,11 +17,13 @@ def load_resource(resource_path):
     resource_content = pkg_resources.resource_string(__name__, resource_path)
     return resource_content
 
-def render_template(template_path, context={}):
+
+def render_template(template_path, context=None):
     """
     Evaluate a template by resource path, applying the provided context
     """
+    if context is None:
+        context = {}
     template_str = load_resource(template_path)
     template = Template(template_str)
     return template.render(Context(context))
-