Add signal html_page_start

src/pretix/base/templatetags/eventsignal.py

@@ -25,3 +25,22 @@ def eventsignal(event: Event, signame: str, **kwargs):
         if response:
             _html.append(response)
     return mark_safe("".join(_html))
+
+
+@register.simple_tag
+def signal(signame: str, request, **kwargs):
+    """
+    Send a signal and return the concatenated return values of all responses.
+
+    Usage::
+
+        {% signal request "path.to.signal" argument="value" ... %}
+    """
+    sigstr = signame.rsplit('.', 1)
+    sigmod = importlib.import_module(sigstr[0])
+    signal = getattr(sigmod, sigstr[1])
+    _html = []
+    for receiver, response in signal.send(request, **kwargs):
+        if response:
+            _html.append(response)
+    return mark_safe("".join(_html))