From 7472564c264f48a699e77843fbdbc09bdf7e8c14 Mon Sep 17 00:00:00 2001
From: Richard Schreiber <schreiber@rami.io>
Date: Fri, 9 May 2025 08:38:34 +0200
Subject: [PATCH] [A11y] Fix sneak-peek for cart (#5076)

---
 .../pretixpresale/event/checkout_base.html    |  8 +-
 src/pretix/static/pretixbase/js/details.js    | 80 ++++++++++---------
 .../static/pretixpresale/scss/main.scss       | 17 +++-
 3 files changed, 65 insertions(+), 40 deletions(-)

diff --git a/src/pretix/presale/templates/pretixpresale/event/checkout_base.html b/src/pretix/presale/templates/pretixpresale/event/checkout_base.html
index f9022a96d..2bcb9e6ec 100644
--- a/src/pretix/presale/templates/pretixpresale/event/checkout_base.html
+++ b/src/pretix/presale/templates/pretixpresale/event/checkout_base.html
@@ -13,7 +13,7 @@
 {% endblock %}
 {% block content %}
 <aside aria-label="{% trans "Your cart" %}">
-    <details class="panel panel-default cart{% if "open_cart" not in request.GET %} sneak-peek{% endif %}" {% if "open_cart" in request.GET %}open{% endif %}>
+    <details class="panel panel-default cart sneak-peek-container" open>
         <summary class="panel-heading">
             <h2 class="panel-title">
                 <span>
@@ -33,11 +33,15 @@
         </summary>
         {% if "open_cart" not in request.GET %}
         <p class="sneak-peek-trigger">
-            <button type="button" class="btn btn-default">{% trans "Show full cart" %}</button>
+            <button type="button" class="btn btn-default" aria-controls="cart-foldable-container">{% trans "Show full cart" %}</button>
         </p>
         {% endif %}
         <div>
+            {% if "open_cart" not in request.GET %}
+            <div class="panel-body sneak-peek-content" id="cart-foldable-container">
+            {% else %}
             <div class="panel-body">
+            {% endif %}
                 {% include "pretixpresale/event/fragment_cart.html" with cart=cart event=request.event %}
             </div>
         </div>
diff --git a/src/pretix/static/pretixbase/js/details.js b/src/pretix/static/pretixbase/js/details.js
index 18beb0bcb..fdcd8eebd 100644
--- a/src/pretix/static/pretixbase/js/details.js
+++ b/src/pretix/static/pretixbase/js/details.js
@@ -2,39 +2,56 @@
 
 setup_collapsible_details = function (el) {
 
-    el.find('details.sneak-peek:not([open])').each(function() {
-        this.open = true;
-        var $elements = $("> :not(summary)", this).show().filter(':not(.sneak-peek-trigger)');
-        var container = this;
-
-        if (Array.prototype.reduce.call($elements, function (h, e) {
-            return h + $(e).outerHeight();
-        }, 0) < 200) {
-            $(".sneak-peek-trigger", this).remove();
-            $(container).removeClass('sneak-peek');
-            container.style.removeProperty('height');
+    el.find('.sneak-peek-trigger').each(function() {
+        var trigger = this;
+        var button = this.querySelector('button');
+        var content = document.getElementById(button.getAttribute('aria-controls'));
+        if (content.scrollHeight < 200) {
+            trigger.remove();
+            content.classList.remove('sneak-peek-content');
             return;
         }
+        content.setAttribute('aria-hidden', 'true');
+        button.setAttribute('aria-expanded', 'false');
+        button.addEventListener('click', function (e) {
+            button.setAttribute('aria-expanded', 'true');
+            content.setAttribute('aria-hidden', 'false');
 
-        $elements.attr('aria-hidden', 'true');
-
-        var trigger = $('summary, .sneak-peek-trigger button', container);
-        function onclick(e) {
-            e.preventDefault();
-
-            container.addEventListener('transitionend', function() {
-                $(container).removeClass('sneak-peek');
-                container.style.removeProperty('height');
+            content.addEventListener('transitionend', function() {
+                content.classList.remove('sneak-peek-content');
+                content.style.removeProperty('height');
+                // we need to keep the trigger/button in the DOM to not irritate screenreaders toggling visibility
+                trigger.classList.add('sr-only');
             }, {once: true});
-            container.style.height = container.scrollHeight + 'px';
-            $('.sneak-peek-trigger', container).fadeOut(function() {
-                $(this).remove();
-            });
-            $elements.removeAttr('aria-hidden');
+            content.style.height = content.scrollHeight + 'px';
 
-            trigger.off('click', onclick);
+            button.addEventListener('click', function (e) {
+                // this will be called by screenreader users if they kept focus on the button after expanding
+                // we need to keep the trigger/button in the DOM to not irritate screenreaders toggling visibility
+                var expanded = button.getAttribute('aria-expanded') == 'true';
+                button.setAttribute('aria-expanded', !expanded);
+                content.setAttribute('aria-hidden', expanded);
+            });
+            button.addEventListener('blur', function (e) {
+                // if content is visible and the user leaves the button, we can safely remove the trigger/button
+                if (button.getAttribute('aria-expanded') == 'true') {
+                    trigger.remove();
+                }
+            });
+        }, { once: true });
+
+        var container = this.closest('details.sneak-peek-container');
+        if (container) {
+            function removeSneekPeakWhenClosed(e) {
+                if (e.newState == "closed") {
+                    container.removeEventListener("toggle", removeSneekPeakWhenClosed);
+                    trigger.remove();
+                    content.removeAttribute('aria-hidden');
+                    content.classList.remove('sneak-peek-content');
+                }
+            }
+            container.addEventListener("toggle", removeSneekPeakWhenClosed);
         }
-        trigger.on('click', onclick);
     });
 
     var isOpera = Object.prototype.toString.call(window.opera) == '[object Opera]';
@@ -43,10 +60,6 @@ setup_collapsible_details = function (el) {
             return true;
         }
         var $details = $(this).closest("details");
-        if ($details.hasClass('sneak-peek')) {
-            // if sneak-peek is active, needs to be handled differently
-            return true;
-        }
         var isOpen = $details.prop("open");
         var $detailsNotSummary = $details.children(':not(summary)');
         if ($detailsNotSummary.is(':animated')) {
@@ -70,11 +83,6 @@ setup_collapsible_details = function (el) {
         if (32 == event.keyCode || (13 == event.keyCode && !isOpera)) {
             // Space or Enter is pressed — trigger the `click` event on the `summary` element
             // Opera already seems to trigger the `click` event when Enter is pressed
-            var $details = $(this).closest("details");
-            if ($details.hasClass('sneak-peek')) {
-                // if sneak-peek is active, needs to be handled differently
-                return true;
-            }
             event.preventDefault();
             $(this).click();
         }
diff --git a/src/pretix/static/pretixpresale/scss/main.scss b/src/pretix/static/pretixpresale/scss/main.scss
index fa0142c89..89bcb99af 100644
--- a/src/pretix/static/pretixpresale/scss/main.scss
+++ b/src/pretix/static/pretixpresale/scss/main.scss
@@ -521,12 +521,17 @@ details summary {
     transform: rotate(-90deg);
 }
 
-details.sneak-peek {
+.sneak-peek-container {
     position: relative;
-    height: 11em;
+}
+.sneak-peek-content {
+    height: 8em;
     overflow: hidden;
     transition: height .5s;
 }
+.nojs .sneak-peek-content {
+    height: auto;
+}
 .sneak-peek-trigger {
     display: grid;
     justify-content: center;
@@ -540,6 +545,14 @@ details.sneak-peek {
     bottom: 0;
     left: 0;
     z-index: 10;
+    opacity: 1;
+    transition: opacity .5s;
+}
+.nojs .sneak-peek-trigger {
+    display: none;
+}
+.sneak-peek-trigger:has(button[aria-expanded="true"]) {
+    opacity: 0;
 }
 
 form.download-btn-form {