Add metadata to DisplayObject (#10614)

The aim of this PR is to get it so that DisplayObject has a metadata API that can be inherited by it's subclasses.

One of the challenges in designing this is to not destroy those subclasses that had already defined their own metadata API (such as Image). 

This also adds a way for SVG objects to surface metadata when returned or displayed.

IPython/core/display.py

@@ -17,6 +17,7 b' import os'
 import struct
 import sys
 import warnings
+from copy import deepcopy
 
 from IPython.utils.py3compat import cast_unicode
 from IPython.testing.skipdoctest import skip_doctest
@@ -281,6 +282,8 b' def display(*objs, include=None, exclude=None, metadata=None, transient=None, di'
     raw = kwargs.pop('raw', False)
     if transient is None:
         transient = {}
+    if metadata is None:
+        metadata={}
     if display_id:
         if display_id is True:
             display_id = _new_id()
@@ -568,8 +571,9 b' class DisplayObject(object):'
 
     _read_flags = 'r'
     _show_mem_addr = False
+    metadata = None
 
-    def __init__(self, data=None, url=None, filename=None):
+    def __init__(self, data=None, url=None, filename=None, metadata=None):
         """Create a display object given raw data.
 
         When this object is returned by an expression or passed to the
@@ -587,6 +591,8 b' class DisplayObject(object):'
             A URL to download the data from.
         filename : unicode
             Path to a local file to load the data from.
+        metadata : dict
+            Dict of metadata associated to be the object when displayed
         """
         if data is not None and isinstance(data, str):
             if data.startswith('http') and url is None:
@@ -602,6 +608,11 b' class DisplayObject(object):'
         self.url = url
         self.filename = filename
 
+        if metadata is not None:
+            self.metadata = metadata
+        elif self.metadata is None:
+            self.metadata = {}
+
         self.reload()
         self._check_data()
 
@@ -617,6 +628,13 b' class DisplayObject(object):'
         """Override in subclasses if there's something to check."""
         pass
 
+    def _data_and_metadata(self):
+        """shortcut for returning metadata with shape information, if defined"""
+        if self.metadata:
+            return self.data, deepcopy(self.metadata)
+        else:
+            return self.data
+
     def reload(self):
         """Reload the raw data from file or URL."""
         if self.filename is not None:
@@ -715,9 +733,9 b' class SVG(DisplayObject):'
             pass
         svg = cast_unicode(svg)
         self._data = svg
-
+    
     def _repr_svg_(self):
-        return self.data
+        return self._data_and_metadata()
 
 
 class JSON(DisplayObject):
@@ -1061,8 +1079,14 b' class Image(DisplayObject):'
         self.height = height
         self.retina = retina
         self.unconfined = unconfined
-        self.metadata = metadata
-        super(Image, self).__init__(data=data, url=url, filename=filename)
+        super(Image, self).__init__(data=data, url=url, filename=filename, 
+                metadata=metadata)
+
+        if self.width is None and self.metadata.get('width', {}):
+            self.width = metadata['width']
+
+        if self.height is None and self.metadata.get('height', {}):
+            self.height = metadata['height']
 
         if retina:
             self._retina_shape()
@@ -1107,14 +1131,14 b' class Image(DisplayObject):'
     def _data_and_metadata(self):
         """shortcut for returning metadata with shape information, if defined"""
         md = {}
+        if self.metadata:
+            md.update(self.metadata)
         if self.width:
             md['width'] = self.width
         if self.height:
             md['height'] = self.height
         if self.unconfined:
             md['unconfined'] = self.unconfined
-        if self.metadata:
-            md.update(self.metadata)
         if md:
             return self.data, md
         else:

IPython/core/tests/test_display.py

@@ -22,6 +22,8 b' def test_image_size():'
     thisurl = 'http://www.google.fr/images/srpr/logo3w.png'
     img = display.Image(url=thisurl, width=200, height=200)
     nt.assert_equal(u'<img src="%s" width="200" height="200"/>' % (thisurl), img._repr_html_())
+    img = display.Image(url=thisurl, metadata={'width':200, 'height':200})
+    nt.assert_equal(u'<img src="%s" width="200" height="200"/>' % (thisurl), img._repr_html_())
     img = display.Image(url=thisurl, width=200)
     nt.assert_equal(u'<img src="%s" width="200"/>' % (thisurl), img._repr_html_())
     img = display.Image(url=thisurl)