Enable/disable save and submit buttons based on input text

apps/openassessment/templates/openassessmentblock/response/oa_response.html

@@ -44,7 +44,7 @@
 
                     <ul class="list list--actions response__submission__actions">
                         <li class="list--actions__item">
-                            <button type="submit" id="submission__save" class="action action--save submission__save">Save Your Progress</button>
+                            <button type="submit" id="submission__save" class="action action--save submission__save is--disabled">Save Your Progress</button>
                             <span class="tip">You may continue to work on your response until you submit it.</span>
                         </li>
                     </ul>
@@ -54,7 +54,7 @@
             <div class="step__actions">
                 <ul class="list list--actions">
                     <li class="list--actions__item">
-                        <a aria-role="button" href="#" id="step--response__submit" class="action action--submit step--response__submit">
+                        <a aria-role="button" href="#" id="step--response__submit" class="action action--submit step--response__submit is--disabled">
                             <span class="copy">Submit your response and move to the next step</span>
                             <i class="ico icon-caret-right"></i>
                         </a>

apps/openassessment/xblock/static/js/src/oa_base.js

@@ -68,6 +68,15 @@ OpenAssessment.BaseUI.prototype = {
                 var sel = $('#openassessment__response', ui.element);
                 sel.replaceWith(html);
 
+                // Install change handler for textarea (to enable submission button)
+                $('#submission__answer__value', ui.element).keyup(
+                    function(eventData) {
+                        var blankSubmission = ($(this).val() === '');
+                        $('#step--response__submit', ui.element).toggleClass('is--disabled', blankSubmission);
+                        $('#submission__save', ui.element).toggleClass('is--disabled', blankSubmission);
+                    }
+                );
+
                 // Install a click handler for submission
                 $('#step--response__submit', ui.element).click(
                     function(eventObject) { ui.submit(); }