Badges: Create templates for common paper sizes (#3660)

* Badges: Create templates for common paper sizes

* Add more sizes

* format lazy

src/pretix/plugins/badges/views.py

@@ -23,9 +23,11 @@ import json
 from datetime import timedelta
 from io import BytesIO
 
+from _decimal import Decimal
 from django.contrib import messages
 from django.contrib.staticfiles import finders
 from django.core.files import File
+from django.core.files.base import ContentFile
 from django.core.files.storage import default_storage
 from django.db import transaction
 from django.http import Http404
@@ -37,6 +39,7 @@ from django.utils.timezone import now
 from django.utils.translation import gettext_lazy as _
 from django.views import View
 from django.views.generic import CreateView, DetailView, ListView
+from pypdf import PdfWriter
 from reportlab.lib import pagesizes
 from reportlab.pdfgen import canvas
 
@@ -51,6 +54,7 @@ from pretix.plugins.badges.tasks import badges_create_pdf
 
 from ...helpers.compat import CompatDeleteView
 from .models import BadgeLayout
+from .templates import TEMPLATES
 
 
 class LayoutListView(EventPermissionRequiredMixin, ListView):
@@ -71,14 +75,32 @@ class LayoutCreate(EventPermissionRequiredMixin, CreateView):
     context_object_name = 'layout'
     success_url = '/ignored'
 
+    def get_form(self, form_class=None):
+        form = super().get_form(form_class)
+        if self.copy_from:
+            del form.fields['template']
+        return form
+
     @transaction.atomic
     def form_valid(self, form):
         form.instance.event = self.request.event
         if not self.request.event.badge_layouts.filter(default=True).exists():
             form.instance.default = True
         messages.success(self.request, _('The new badge layout has been created.'))
+        if not self.copy_from:
+            form.instance.layout = json.dumps(TEMPLATES[form.cleaned_data["template"]]["layout"])
         super().form_valid(form)
-        if form.instance.background and form.instance.background.name:
+        if not self.copy_from:
+            p = PdfWriter()
+            p.add_blank_page(
+                width=Decimal('%.5f' % TEMPLATES[form.cleaned_data["template"]]["pagesize"][0]),
+                height=Decimal('%.5f' % TEMPLATES[form.cleaned_data["template"]]["pagesize"][1]),
+            )
+            buffer = BytesIO()
+            p.write(buffer)
+            buffer.seek(0)
+            form.instance.background.save('background.pdf', ContentFile(buffer.read()))
+        elif form.instance.background and form.instance.background.name:
             form.instance.background.save('background.pdf', form.instance.background)
         form.instance.log_action('pretix.plugins.badges.layout.added', user=self.request.user,
                                  data=dict(form.cleaned_data))