Create generic field display registry to render model fields in the admin

wagtail/admin/ui/fields.py

@@ -0,0 +1,40 @@
+from django.core.exceptions import ImproperlyConfigured
+from django.db import models
+
+from wagtail.admin.ui.components import Component
+from wagtail.utils.registry import ModelFieldRegistry
+
+display_class_registry = ModelFieldRegistry()
+
+
+def register_display_class(field_class, to=None, display_class=None, exact_class=False):
+    """
+    Define how model field values should be rendered in the admin.
+    The `display_class` should be a subclass of `wagtail.admin.ui.components.Component`
+    that takes a single argument in its constructor: the value of the field.
+
+    This is mainly useful for defining how fields are rendered in the inspect view,
+    but it can also be used in other places, e.g. listing views.
+    """
+
+    if display_class is None:
+        raise ImproperlyConfigured(
+            "register_display_class must be passed a 'display_class' keyword argument"
+        )
+
+    if to and field_class != models.ForeignKey:
+        raise ImproperlyConfigured(
+            "The 'to' argument on register_display_class is only valid for ForeignKey fields"
+        )
+
+    display_class_registry.register(
+        field_class, to=to, value=display_class, exact_class=exact_class
+    )
+
+
+class BaseFieldDisplay(Component):
+    def __init__(self, value):
+        self.value = value
+
+    def get_context_data(self, parent_context):
+        return {"value": self.value}

wagtail/documents/apps.py

@@ -1,6 +1,9 @@
 from django.apps import AppConfig
+from django.db.models import ForeignKey
 from django.utils.translation import gettext_lazy as _
 
+from . import get_document_model
+
 
 class WagtailDocsAppConfig(AppConfig):
     name = "wagtail.documents"
@@ -13,7 +16,14 @@ class WagtailDocsAppConfig(AppConfig):
 
         register_signal_handlers()
 
-        from wagtail.documents import get_document_model
+        Document = get_document_model()
+
+        from wagtail.admin.ui.fields import register_display_class
+
+        from .components import DocumentDisplay
+
+        register_display_class(ForeignKey, to=Document, display_class=DocumentDisplay)
+
         from wagtail.models.reference_index import ReferenceIndex
 
-        ReferenceIndex.register_model(get_document_model())
+        ReferenceIndex.register_model(Document)

wagtail/documents/components.py

@@ -0,0 +1,5 @@
+from wagtail.admin.ui.fields import BaseFieldDisplay
+
+
+class DocumentDisplay(BaseFieldDisplay):
+    template_name = "wagtaildocs/components/document_display.html"

wagtail/documents/templates/wagtaildocs/components/document_display.html

@@ -0,0 +1 @@
+<a href="{{ value.url }}">{{ value.title }} <span class="meta">({{ value.file_extension|upper }}, {{ value.file.size|filesizeformat }})</span></a>

wagtail/images/apps.py

@@ -36,6 +36,12 @@ class WagtailImagesAppConfig(AppConfig):
             ForeignKey, to=Image, comparison_class=ImageFieldComparison
         )
 
+        from wagtail.admin.ui.fields import register_display_class
+
+        from .components import ImageDisplay
+
+        register_display_class(ForeignKey, to=Image, display_class=ImageDisplay)
+
         from wagtail.models.reference_index import ReferenceIndex
 
-        ReferenceIndex.register_model(get_image_model())
+        ReferenceIndex.register_model(Image)

wagtail/images/components.py

@@ -0,0 +1,9 @@
+from wagtail.admin.ui.fields import BaseFieldDisplay
+from wagtail.images.shortcuts import get_rendition_or_not_found
+
+
+class ImageDisplay(BaseFieldDisplay):
+    rendition_spec = "max-400x400"
+
+    def render_html(self, parent_context):
+        return get_rendition_or_not_found(self.value, self.rendition_spec).img_tag()