Use _repr_mimebundle_ in IPython 6.1 or later.

Fixes jupyter-widgets#1811

ipywidgets/widgets/widget.py

@@ -9,6 +9,7 @@
 import collections
 import sys
 
+from IPython import version_info as ipython_version_info
 from IPython.core.getipython import get_ipython
 from ipykernel.comm import Comm
 from traitlets.utils.importstring import import_item
@@ -19,6 +20,7 @@
 from IPython.display import display
 from json import loads as jsonloads, dumps as jsondumps
 
+
 from base64 import standard_b64decode, standard_b64encode
 
 from .._version import __protocol_version__, __jupyter_widgets_base_version__
@@ -466,6 +468,7 @@ def close(self):
             self.comm.close()
             self.comm = None
             self._ipython_display_ = None
+            self._repr_mimebundle_ = None
 
     def send_state(self, key=None):
         """Sends the widget state, or a piece of it, to the front-end, if it exists.
@@ -697,9 +700,12 @@ def _trait_from_json(x, self):
         """Convert json values to objects."""
         return x
 
-    def _ipython_display_(self, **kwargs):
-        """Called when `IPython.display.display` is called on the widget."""
+    def _repr_mimebundle_(self, **kwargs):
+        """Called when `IPython.display.display` is called."""
         if self._view_name is not None:
+            # This callback now happens *before* the actual display call,
+            # whereas before it happened *after* the display call.
+            self._handle_displayed(**kwargs)
 
             plaintext = repr(self)
             if len(plaintext) > 110:
@@ -717,9 +723,21 @@ def _ipython_display_(self, **kwargs):
                     'model_id': self._model_id
                 }
             }
-            display(data, raw=True)
+            return data
 
-            self._handle_displayed(**kwargs)
+    def _ipython_display_(self, **kwargs):
+        """Called when `IPython.display.display` is called on a widget.
+
+        Note: if we are in IPython 6.1 or later, we return NotImplemented so
+        that _repr_mimebundle_ is used directly.
+        """
+        if (ipython_version_info[0] > 6
+            or (ipython_version_info[0] == 6 and ipython_version_info[1] >= 1)):
+            raise NotImplementedError
+
+        data = self._repr_mimebundle_(**kwargs)
+        if data:
+            display(data, raw=True)
 
     def _send(self, msg, buffers=None):
         """Sends a message to the model in the front-end."""