Show percentage of discount in cart (Z#23176955) (#4719)

* Show percentage of discount in cart (Z#23176955)

* Fix computation

src/pretix/base/models/orders.py

@@ -3218,6 +3218,12 @@ class CartPosition(AbstractPosition):
             self.tax_code = line_price.code
             self.save(update_fields=['line_price_gross', 'tax_rate'])
 
+    @property
+    def discount_percentage(self):
+        if not self.line_price_gross:
+            return 0
+        return (self.line_price_gross - self.price) / self.line_price_gross * 100
+
     @property
     def addons_without_bundled(self):
         addons = [op for op in self.addons.all() if not op.is_bundled]

src/pretix/presale/templates/pretixpresale/event/fragment_cart.html

@@ -268,8 +268,14 @@
                         {% if line.discount and line.line_price_gross != line.price %}
                             <span class="text-success discounted" data-toggle="tooltip" title="{% trans "The price of this product was reduced because of an automatic discount." %}">
                                 <br>
-                                <span class="fa fa-percent fa-fw" aria-hidden="true"></span>
+                                <span class="fa fa-star fa-fw" aria-hidden="true"></span>
+                                {% if line.price < line.line_price_gross %}
+                                    {% blocktranslate trimmed with percent=line.discount_percentage|floatformat:0 %}
+                                        {{ percent }} % Discount
+                                    {% endblocktranslate %}
+                                {% else %}
                                     {% trans "Discounted" %}
+                                {% endif %}
                             </span>
                         {% endif %}
                     </div>
@@ -335,8 +341,14 @@
                         {% if line.discount and line.line_price_gross != line.price %}
                             <span class="text-success discounted" data-toggle="tooltip" title="{% trans "The price of this product was reduced because of an automatic discount." %}">
                                 <br>
-                                <span class="fa fa-percent fa-fw" aria-hidden="true"></span>
+                                <span class="fa fa-star fa-fw" aria-hidden="true"></span>
+                                {% if line.price < line.line_price_gross %}
+                                    {% blocktranslate trimmed with percent=line.discount_percentage|floatformat:0 %}
+                                        {{ percent }} % Discount
+                                    {% endblocktranslate %}
+                                {% else %}
                                     {% trans "Discounted" %}
+                                {% endif %}
                             </span>
                         {% endif %}
                     </div>