Customize @@display-file to allow to download files with proper filename

CHANGES.rst

@@ -4,7 +4,9 @@ Changelog
 4.0.11 (unreleased)
 -------------------
 
-- Nothing changed yet.
+- Customize @@display-file to allow to download files with proper filename.
+  (backport of https://github.com/RedTurtle/redturtle.volto/pull/113).
+  [cekk]
 
 
 4.0.10 (2024-07-12)

src/design/plone/policy/browser/configure.zcml

@@ -20,5 +20,13 @@
       permission="zope2.View"
       />
 
+  <!-- backport of https://github.com/RedTurtle/redturtle.volto/pull/113 -->
+  <browser:page
+      name="display-file"
+      for="*"
+      class=".display_file.DisplayFile"
+      permission="zope2.View"
+      layer="design.plone.policy.interfaces.IDesignPlonePolicyLayer"
+      />
 
 </configure>

src/design/plone/policy/browser/display_file.py

@@ -0,0 +1,29 @@
+from plone.namedfile.browser import DisplayFile as BaseView
+from urllib.parse import quote
+
+
+class DisplayFile(BaseView):
+    """
+    Custom view
+    """
+
+    def set_headers(self, file):
+        """
+        backport of https://github.com/RedTurtle/redturtle.volto/pull/113
+
+        We need to add filename to the reponse because otherwise the browser
+        use the field name as filename (last path element).
+
+        content-disposition should be "inline" to allow to display the file in the browser
+        without forcing download (with "attachment" the browser will download it).
+        """
+        super().set_headers(file=file)
+
+        filename = getattr(file, "filename", "")
+        if filename is not None:
+            if not isinstance(filename, str):
+                filename = str(filename, "utf-8", errors="ignore")
+            filename = quote(filename.encode("utf8"))
+            self.request.response.setHeader(
+                "Content-Disposition", f"inline; filename*=UTF-8''{filename}"
+            )