Support for multiple display output formats in the notebook

holoviews/core/options.py

@@ -769,6 +769,10 @@ class Store(object):
     # types grouped by the backend. Set using the register method.
     registry = {}
 
+    # A list of formats to be published for display on the frontend (e.g
+    # IPython Notebook or a GUI application)
+    display_formats = ['html']
+
     # Once register_plotting_classes is called, this OptionTree is
     # populated for the given backend.
     _options = {}

holoviews/ipython/__init__.py

@@ -105,6 +105,16 @@ class notebook_extension(param.ParameterizedFunction):
     width = param.Number(default=None, bounds=(0, 100), doc="""
         Width of the notebook as a percentage of the browser screen window width.""")
 
+    display_formats = param.List(default=['html'], doc="""
+        A list of formats that are rendered to the notebook where
+        multiple formats may be selected at once (although only one
+        format will be displayed).
+
+        Although the 'html' format is supported across backends, other
+        formats supported by the current backend (e.g 'png' and 'svg'
+        using the matplotlib backend) may be used. This may be useful to
+        export figures to other formats such as PDF with nbconvert. """)
+
     ip = param.Parameter(default=None, doc="IPython kernel instance")
 
     _loaded = False
@@ -113,6 +123,13 @@ def __call__(self, **params):
         resources = self._get_resources(params)
         ip = params.pop('ip', None)
         p = param.ParamOverrides(self, params)
+        Store.display_formats = p.display_formats
+
+        if 'html' not in p.display_formats and len(p.display_formats) > 1:
+            msg = ('Output magic unable to control displayed format '
+                   'as IPython notebook uses fixed precedence '
+                   'between %r' % p.display_formats)
+            display(HTML('<b>Warning</b>: %s' % msg))
 
         if notebook_extension._loaded == False:
             ip = get_ipython() if ip is None else ip

holoviews/ipython/display_hooks.py

@@ -188,13 +188,59 @@ def display(obj, raw=False, **kwargs):
 
 
 def pprint_display(obj):
-    # If pretty printing is off, return None (will fallback to repr)
+    if 'html' not in Store.display_formats:
+        return None
+
+    # If pretty printing is off, return None (fallback to next display format)
     ip = get_ipython()  #  # pyflakes:ignore (in IPython namespace)
     if not ip.display_formatter.formatters['text/plain'].pprint:
         return None
     return display(obj, raw=True)
 
 
+@display_hook
+def element_png_display(element, max_frames, max_branches):
+    """
+    Used to render elements to PNG if requested in the display formats.
+    """
+    if 'png' not in Store.display_formats:
+        return None
+    info = process_object(element)
+    if info: return info
+
+    backend = Store.current_backend
+    if type(element) not in Store.registry[backend]:
+        return None
+    renderer = Store.renderers[backend]
+    # Current renderer does not support PNG
+    if 'png' not in renderer.params('fig').objects:
+        return None
+
+    data, info = renderer(element, fmt='png')
+    return data
+
+
+@display_hook
+def element_svg_display(element, max_frames, max_branches):
+    """
+    Used to render elements to SVG if requested in the display formats.
+    """
+    if 'svg' not in Store.display_formats:
+        return None
+    info = process_object(element)
+    if info: return info
+
+    backend = Store.current_backend
+    if type(element) not in Store.registry[backend]:
+        return None
+    renderer = Store.renderers[backend]
+    # Current renderer does not support SVG
+    if 'svg' not in renderer.params('fig').objects:
+        return None
+    data, info = renderer(element, fmt='svg')
+    return data
+
+
 # display_video output by default, but may be set to first_frame,
 # middle_frame or last_frame (e.g. for testing purposes)
 render_anim = None
@@ -205,3 +251,9 @@ def set_display_hooks(ip):
     html_formatter.for_type(UniformNdMapping, pprint_display)
     html_formatter.for_type(AdjointLayout, pprint_display)
     html_formatter.for_type(Layout, pprint_display)
+
+    png_formatter = ip.display_formatter.formatters['image/png']
+    png_formatter.for_type(ViewableElement, element_png_display)
+
+    svg_formatter = ip.display_formatter.formatters['image/svg+xml']
+    svg_formatter.for_type(ViewableElement, element_svg_display)

holoviews/ipython/magics.py

@@ -60,6 +60,7 @@ def update_options(cls, options, items):
         Allows updating options depending on class attributes
         and unvalidated options.
         """
+        pass
 
     @classmethod
     def get_options(cls, line, options, linemagic):
@@ -98,10 +99,10 @@ def get_options(cls, line, options, linemagic):
                         raise ValueError("Value %r for key %r not between %s and %s" % info)
                 options[keyword] = value
 
-        return cls._validate(options, linemagic)
+        return cls._validate(options, items, linemagic)
 
     @classmethod
-    def _validate(cls, options, linemagic):
+    def _validate(cls, options, items, linemagic):
         "Allows subclasses to check options are valid."
         raise NotImplementedError("OptionsMagic is an abstract base class.")
 
@@ -303,8 +304,16 @@ def _generate_docstring(cls):
 
 
     @classmethod
-    def _validate(cls, options, linemagic):
+    def _validate(cls, options, items, linemagic):
         "Validation of edge cases and incompatible options"
+
+        if 'html' in Store.display_formats:
+            pass
+        elif 'fig' in items and items['fig'] not in Store.display_formats:
+            msg = ("Output magic requesting figure format %r " % items['fig']
+                   + "not in display formats %r" % Store.display_formats)
+            display(HTML("<b>Warning:</b> %s" % msg))
+
         backend = Store.current_backend
         return Store.renderers[backend].validate(options)