Allow ticket output providers to handle downloads externally (#1402)

* TicketOutput-Providers: Make preview optional; download/attachable optional; optional specific target; update doc

* Spelling fixes in doc

* Changes after code-review

* Changes after code-review

* Commit missing template file

* Allow for redirects instead of files

* Return HTTPResponse with Content-Type text/uri-list on API

* Update API-doc

* Add viewable to spellinglist, fixing doc-test

src/pretix/control/templates/pretixcontrol/event/tickets.html

@@ -29,7 +29,7 @@
                     <div class="panel panel-default ticketoutput-panel">
                         <div class="panel-heading">
                             <a href="{% url "control:event.settings.tickets.preview" event=request.event.slug organizer=request.organizer.slug output=provider.identifier %}"
-                                    class="btn btn-default btn-sm pull-right flip {% if not provider.preview_allowed %}disabled{% endif %}"
+                                    class="btn btn-default btn-sm pull-right flip {% if not provider.evaluated_preview_allowed %}disabled{% endif %}"
                                     target="_blank">
                                 {% trans "Preview" %}
                             </a>

src/pretix/control/templates/pretixcontrol/order/index.html

@@ -287,7 +287,7 @@
                                             {% for b in download_buttons %}
                                                 <form action="{% url "control:event.order.download.ticket" code=order.code event=request.event.slug organizer=request.event.organizer.slug position=line.pk output=b.identifier %}"
                                                         method="post" data-asynctask data-asynctask-download
-                                                        class="form-inline helper-display-inline">
+                                                        class="form-inline helper-display-inline{% if b.javascript_required %} requirejs{% endif %}">
                                                     {% csrf_token %}
                                                     <button type="submit"
                                                             class="btn btn-xs btn-default">

src/pretix/control/views/event.py

@@ -736,11 +736,14 @@ class TicketSettings(EventSettingsViewMixin, EventPermissionRequiredMixin, FormV
             provider.settings_content = provider.settings_content_render(self.request)
             provider.form.prepare_fields()
 
-            provider.preview_allowed = True
-            for k, v in provider.settings_form_fields.items():
-                if v.required and not self.request.event.settings.get('ticketoutput_%s_%s' % (provider.identifier, k)):
-                    provider.preview_allowed = False
-                    break
+            provider.evaluated_preview_allowed = True
+            if not provider.preview_allowed:
+                provider.evaluated_preview_allowed = False
+            else:
+                for k, v in provider.settings_form_fields.items():
+                    if v.required and not self.request.event.settings.get('ticketoutput_%s_%s' % (provider.identifier, k)):
+                        provider.evaluated_preview_allowed = False
+                        break
 
             providers.append(provider)
         return providers

src/pretix/control/views/orders.py

@@ -16,7 +16,8 @@ from django.db.models import (
 )
 from django.forms import formset_factory
 from django.http import (
-    FileResponse, Http404, HttpResponseNotAllowed, JsonResponse,
+    FileResponse, Http404, HttpResponseNotAllowed, HttpResponseRedirect,
+    JsonResponse,
 )
 from django.shortcuts import get_object_or_404, redirect, render
 from django.urls import reverse
@@ -225,7 +226,8 @@ class OrderDetail(OrderView):
                 'text': provider.download_button_text or 'Ticket',
                 'icon': provider.download_button_icon or 'fa-download',
                 'identifier': provider.identifier,
-                'multi': provider.multi_download_enabled
+                'multi': provider.multi_download_enabled,
+                'javascript_required': provider.javascript_required
             })
         return buttons
 
@@ -340,12 +342,16 @@ class OrderDownload(AsyncAction, OrderView):
                 'message': str(self.get_success_message(value))
             })
         if isinstance(value, CachedTicket):
-            resp = FileResponse(value.file.file, content_type=value.type)
-            resp['Content-Disposition'] = 'attachment; filename="{}-{}-{}-{}{}"'.format(
-                self.request.event.slug.upper(), self.order.code, self.order_position.positionid,
-                self.output.identifier, value.extension
-            )
-            return resp
+            if value.type == 'text/uri-list':
+                resp = HttpResponseRedirect(value.file.file.read())
+                return resp
+            else:
+                resp = FileResponse(value.file.file, content_type=value.type)
+                resp['Content-Disposition'] = 'attachment; filename="{}-{}-{}-{}{}"'.format(
+                    self.request.event.slug.upper(), self.order.code, self.order_position.positionid,
+                    self.output.identifier, value.extension
+                )
+                return resp
         elif isinstance(value, CachedCombinedTicket):
             resp = FileResponse(value.file.file, content_type=value.type)
             resp['Content-Disposition'] = 'attachment; filename="{}-{}-{}{}"'.format(