Initial draft

Author: mrbazzan

djangocms_picture/fields.py

@@ -0,0 +1,90 @@
+from django.contrib.contenttypes.fields import GenericForeignKey
+from django.contrib.contenttypes.models import ContentType
+from django import forms
+from django.db import models
+
+
+class PictureWidget(forms.MultiWidget):
+    def __init__(self):
+        widgets = [
+            forms.Select(attrs={},choices=[
+                # TODO: provide a configuration settings instead of
+                # accessing the db?
+                # Also, check that the provided value exists
+                (ct.id, ct.name) for ct in ContentType.objects.all()
+            ]),
+            forms.NumberInput(attrs={}),
+        ]
+        super().__init__(widgets)
+
+
+class PictureFormField(forms.Field):
+    widget = PictureWidget
+
+    def __init__(self, *args, **kwargs):
+        kwargs.pop('encoder', None)  # passed from models.JSONField
+        kwargs.pop('decoder', None)
+        super().__init__(*args, **kwargs)
+
+    def prepare_value(self, value):
+        data = []
+        if value is None:
+            return data
+
+        ct = ContentType.objects.get_for_model(value)
+        data.extend([ct.id, value.pk])
+        return data
+
+    def to_python(self, value):
+        if not value:
+            return value
+
+        # NOTE: what if we save this in a hidden widget
+        ct_id, fk = value
+
+        ct = ContentType.objects.get_for_id(id=ct_id)
+        obj = ct.get_object_for_this_type(id=fk)
+
+        # This should help us deceive GFK.get_content_type
+        # to get the necessary ct and fk
+        class HelperObj:
+            _state = ct._state
+            pk = int(fk)
+            _meta = ct.model_class()._meta
+
+            def __repr__(this):
+                return f"{this._meta.model_name}({fk})"
+
+        return obj
+
+
+class PictureField(GenericForeignKey, models.Field):
+    def __init__(self, **kwargs):
+        # call to models.JSONField
+        super(GenericForeignKey, self).__init__(**kwargs)
+
+        # call to GenericForeignKey
+        super().__init__(**kwargs)
+        self.editable = True
+
+    def contribute_to_class(self, cls, name):
+        ct = models.ForeignKey(ContentType,
+                               editable=False,
+                               on_delete=models.CASCADE)
+        fk = models.PositiveIntegerField(editable=False)
+
+        self.ct_field = f"{name}_ct"
+        self.fk_field = f"{name}_fk"
+
+        cls.add_to_class(self.ct_field, ct)
+        cls.add_to_class(self.fk_field, fk)
+        super().contribute_to_class(cls, name)
+
+        # this is required by _post_clean hook used during
+        # model validation in forms
+        self.attname = self.name
+
+    def formfield(self, **kwargs):
+        kwargs.setdefault("form_class", PictureFormField)
+        return super().formfield(**kwargs)
+