Add String pane to support any representable object

panel/pane.py

@@ -10,12 +10,18 @@
 import base64
 from io import BytesIO
 
+try:
+    from html import escape
+except:
+    from cgi import escape
+
+
 import param
 
 from bokeh.layouts import Row as _BkRow, WidgetBox as _BkWidgetBox
 from bokeh.models import LayoutDOM, CustomJS, Widget as _BkWidget, Div as _BkDiv
 
-from .util import basestring, get_method_owner, push, remove_root, Div
+from .util import basestring, unicode, get_method_owner, push, remove_root, Div
 from .viewable import Reactive, Viewable
 
 
@@ -32,7 +38,7 @@ class PaneBase(Reactive):
     """
     PaneBase is the abstract baseclass for all atomic displayable units
     in the panel library. Pane defines an extensible interface for
-    wrapping arbitrary objects and transforming them into bokeh models.
+    wrapping arbitrary objects and transforming them into Bokeh models.
 
     Panes are reactive in the sense that when the object they are
     wrapping is changed any dashboard containing the pane will update
@@ -43,12 +49,13 @@ class PaneBase(Reactive):
     """
 
     object = param.Parameter(default=None, doc="""
-        The object being wrapped, which will be converted into a bokeh model.""")
+        The object being wrapped, which will be converted into a Bokeh model.""")
 
-    # When multiple Panes apply to an object the precedence is used
-    precedence = 0
+    # When multiple Panes apply to an object, the one with the highest
+    # numerical precedence is selected. The default is an intermediate value.
+    precedence = 0.5
 
-    # Declares whether Pane supports updates to the bokeh model
+    # Declares whether Pane supports updates to the Bokeh model
     _updates = False
 
     __abstract = True
@@ -66,7 +73,7 @@ def get_pane_type(cls, obj):
         if isinstance(obj, Viewable):
             return type(obj)
         descendents = [(p.precedence, p) for p in param.concrete_descendents(PaneBase).values()]
-        pane_types = sorted(descendents, key=lambda x: x[0])
+        pane_types = reversed(sorted(descendents, key=lambda x: x[0]))
         for _, pane_type in pane_types:
             if not pane_type.applies(obj): continue
             return pane_type
@@ -98,15 +105,15 @@ def _cleanup(self, model, final=False):
 
     def _update(self, model):
         """
-        If _updates=True this method is used to update an existing bokeh
+        If _updates=True this method is used to update an existing Bokeh
         model instead of replacing the model entirely. The supplied model
         should be updated with the current state.
         """
         raise NotImplementedError
 
     def _link_object(self, model, doc, root, parent, comm=None):
         """
-        Links the object parameter to the rendered bokeh model, triggering
+        Links the object parameter to the rendered Bokeh model, triggering
         an update when the object changes.
         """
         def update_pane(change, history=[model]):
@@ -142,16 +149,18 @@ def update_models():
 
 class Bokeh(PaneBase):
     """
-    Bokeh panes allow including any bokeh model in a panel.
+    Bokeh panes allow including any Bokeh model in a panel.
     """
 
+    precedence = 0.8
+
     @classmethod
     def applies(cls, obj):
         return isinstance(obj, LayoutDOM)
 
     def _get_model(self, doc, root=None, parent=None, comm=None):
         """
-        Should return the bokeh model to be rendered.
+        Should return the Bokeh model to be rendered.
         """
         model = self.object
         if isinstance(model, _BkWidget):
@@ -175,9 +184,11 @@ def _get_model(self, doc, root=None, parent=None, comm=None):
 class HoloViews(PaneBase):
     """
     HoloViews panes render any HoloViews object to a corresponding
-    bokeh model while respecting the currently selected backend.
+    Bokeh model while respecting the currently selected backend.
     """
-
+
+    precedence = 0.8
+
     @classmethod
     def applies(cls, obj):
         if 'holoviews' not in sys.modules:
@@ -213,7 +224,7 @@ def _cleanup(self, model, final=False):
 
     def _get_model(self, doc, root=None, parent=None, comm=None):
         """
-        Should return the bokeh model to be rendered.
+        Should return the Bokeh model to be rendered.
         """
         from holoviews import Store
         renderer = Store.renderers[Store.current_backend]
@@ -408,24 +419,6 @@ def _png(self):
         return b.getvalue()
 
 
-class HTML(DivPaneBase):
-    """
-    HTML panes render any object which has a _repr_html_ method and wraps
-    the HTML in a bokeh Div model. The height and width can optionally
-    be specified, to allow room for whatever is being wrapped.
-    """
-
-    precedence = 1
-
-    @classmethod
-    def applies(cls, obj):
-        return hasattr(obj, '_repr_html_')
-
-    def _get_properties(self):
-        properties = super(HTML, self)._get_properties()
-        return dict(properties, text=self.object._repr_html_())
-
-
 class RGGPlot(PNG):
     """
     An RGGPlot panes render an r2py-based ggplot2 figure to png
@@ -450,3 +443,48 @@ def _png(self):
                  res=self.dpi, antialias="subpixel") as b:
             robjects.r("print")(self.object)
         return b.getvalue()
+
+
+class HTML(DivPaneBase):
+    """
+    HTML panes wrap HTML text in a bokeh Div model.  The
+    provided object can either be a text string, or an object that
+    has a `_repr_html_` method that can be called to get the HTML
+    text string.  The height and width can optionally be specified, to
+    allow room for whatever is being wrapped.
+    """
+
+    precedence = 0.2
+
+    @classmethod
+    def applies(cls, obj):
+        return (hasattr(obj, '_repr_html_') or
+                (isinstance(obj, basestring) or
+                 (isinstance(obj, unicode))))
+
+    def _get_properties(self):
+        properties = super(HTML, self)._get_properties()
+        text=self.object
+        if hasattr(text, '_repr_html_'):
+            text=text._repr_html_()
+        return dict(properties, text=text)
+
+
+class Str(DivPaneBase):
+    """
+    A Str pane renders any object for which `str()` can be called,
+    escaping any HTML markup and then wrapping the resulting string in
+    a bokeh Div model.  Set to a low precedence because generally one
+    will want a better representation, but allows arbitrary objects to
+    be used as a Pane (numbers, arrays, objects, etc.).
+    """
+
+    precedence = 0
+
+    @classmethod
+    def applies(cls, obj):
+        return True
+
+    def _get_properties(self):
+        properties = super(Str, self)._get_properties()
+        return dict(properties, text='<pre>'+escape(str(self.object))+'</pre>')

panel/param.py

@@ -57,7 +57,7 @@ class Param(PaneBase):
     label_formatter = param.Callable(default=default_label_formatter, allow_None=True,
         doc="Callable used to format the parameter names into widget labels.")
 
-    precedence = 1
+    precedence = 0.1
 
     _mapping = {
         param.Action:        Button,

panel/plotly.py

@@ -36,6 +36,8 @@ class Plotly(PaneBase):
 
     _updates = True
 
+    precedence = 0.8
+
     def __init__(self, object, layout=None, **params):
         super(Plotly, self).__init__(self._to_figure(object, layout),
                                      layout=layout, **params)

panel/tests/test_panes.py

@@ -7,7 +7,7 @@
                           GlyphRenderer, Circle, Line)
 from bokeh.plotting import Figure
 from panel.pane import (Pane, PaneBase, Bokeh, HoloViews, Matplotlib,
-                        ParamMethod)
+                        ParamMethod, HTML, Str)
 
 try:
     import holoviews as hv
@@ -276,3 +276,55 @@ def test_param_method_pane_changing_type(document, comm):
     # Cleanup pane
     new_pane._cleanup(model)
     assert new_pane._callbacks == {}
+
+
+def test_get_html_pane_type():
+    assert PaneBase.get_pane_type("<h1>Test</h1>") is HTML
+
+
+def test_html_pane(document, comm):
+    pane = Pane("<h1>Test</h1>")
+
+    # Create pane
+    row = pane._get_root(document, comm=comm)
+    assert isinstance(row, BkRow)
+    assert len(row.children) == 1
+    model = row.children[0]
+    assert model.ref['id'] in pane._callbacks
+    div = get_div(model)
+    assert div.text == "<h1>Test</h1>"
+
+    # Replace Pane.object
+    pane.object = "<h2>Test</h2>"
+    model = row.children[0]
+    assert div is get_div(model)
+    assert model.ref['id'] in pane._callbacks
+    assert div.text == "<h2>Test</h2>"
+
+    # Cleanup
+    pane._cleanup(model)
+    assert pane._callbacks == {}
+
+
+def test_string_pane(document, comm):
+    pane = Str("<h1>Test</h1>")
+
+    # Create pane
+    row = pane._get_root(document, comm=comm)
+    assert isinstance(row, BkRow)
+    assert len(row.children) == 1
+    model = row.children[0]
+    assert model.ref['id'] in pane._callbacks
+    div = get_div(model)
+    assert div.text == "<pre>&lt;h1&gt;Test&lt;/h1&gt;</pre>"
+
+    # Replace Pane.object
+    pane.object = "<h2>Test</h2>"
+    model = row.children[0]
+    assert div is get_div(model)
+    assert model.ref['id'] in pane._callbacks
+    assert div.text == "<pre>&lt;h2&gt;Test&lt;/h2&gt;</pre>"
+
+    # Cleanup
+    pane._cleanup(model)
+    assert pane._callbacks == {}