Repr style out for widgets

IPython/core/formatters.py

@@ -149,27 +149,30 b' class DisplayFormatter(Configurable):'
         format_dict = {}
         md_dict = {}
 
-        for format_type, formatter in self.formatters.items():
-            if include and format_type not in include:
-                continue
-            if exclude and format_type in exclude:
-                continue
-            
-            md = None
-            try:
-                data = formatter(obj)
-            except:
-                # FIXME: log the exception
-                raise
-            
-            # formatters can return raw data or (data, metadata)
-            if isinstance(data, tuple) and len(data) == 2:
-                data, md = data
-            
-            if data is not None:
-                format_dict[format_type] = data
-            if md is not None:
-                md_dict[format_type] = md
+        # 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
+                if exclude and format_type in exclude:
+                    continue
+                
+                md = None
+                try:
+                    data = formatter(obj)
+                except:
+                    # FIXME: log the exception
+                    raise
+                
+                # formatters can return raw data or (data, metadata)
+                if isinstance(data, tuple) and len(data) == 2:
+                    data, md = data
+                
+                if data is not None:
+                    format_dict[format_type] = data
+                if md is not None:
+                    md_dict[format_type] = md
             
         return format_dict, md_dict