Better implementation of widget _repr_ style display logic.

IPython/core/displayhook.py

@@ -241,6 +241,9 class DisplayHook(Configurable):
         """
         self.check_for_underscore()
         if result is not None and not self.quiet():
+            # If _ipython_display_ is defined, use that to display this object.  If
+            # it returns NotImplemented, use the _repr_ logic (default).
+            if not hasattr(result, '_ipython_display_') or result._ipython_display_() == NotImplemented:
             self.start_displayhook()
             self.write_output_prompt()
             format_dict, md_dict = self.compute_format_data(result)

IPython/core/formatters.py

@@ -149,9 +149,6 class DisplayFormatter(Configurable):
         format_dict = {}
         md_dict = {}
 
-        # If _ipython_display_ is defined, use that to display this object.  If
-        # it returns NotImplemented, use the _repr_ logic (default).
-        if not hasattr(obj, '_ipython_display_') or obj._ipython_display_(**kwargs) == NotImplemented:
             for format_type, formatter in self.formatters.items():
                 if include and format_type not in include:
                     continue