Table finalize hook fix and example (#1711)

* #1708

* Minor tweak to notebook

* add additional URL
* committing mostly to test failing Travis build

* move file to new directory per @jlstevens suggestion

examples/reference/features/bokeh/table_hooks_example.ipynb

@@ -0,0 +1,77 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import numpy as np\n",
+    "import holoviews as hv\n",
+    "from bokeh.models import HTMLTemplateFormatter\n",
+    "hv.extension('bokeh')"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Declare Data"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "name = ['homepage', 'github', 'chat']\n",
+    "link = ['http://holoviews.org', 'https://github.com/ioam/holoviews', 'https://gitter.im/ioam/holoviews']\n",
+    "table = hv.Table({'Name':name, 'Link':link},  vdims = ['Name', 'Link'],  kdims=[])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Plot"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%%opts Table [width=500]\n",
+    "def apply_format(plot, element):\n",
+    "    plot.handles['plot'].columns[1].formatter=HTMLTemplateFormatter(template='<a href=\"<%= value %>\"><%= value %></a>')\n",
+    "\n",
+    "table.opts(plot=dict(finalize_hooks=[apply_format]))"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.5.3"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}

holoviews/plotting/bokeh/tabular.py

@@ -17,6 +17,11 @@ class TablePlot(BokehPlot, GenericElementPlot):
     style_opts = ['row_headers', 'selectable', 'editable',
                   'sortable', 'fit_columns', 'width', 'height']
 
+    finalize_hooks = param.HookList(default=[], doc="""
+        Optional list of hooks called when finalizing a column.
+        The hook is passed the plot object and the displayed
+        object, and other plotting handles can be accessed via plot.handles.""")
+
     _update_handles = ['source', 'glyph']
 
     def __init__(self, element, plot=None, **params):
@@ -27,6 +32,17 @@ def __init__(self, element, plot=None, **params):
         self.callbacks = [] # Callback support on tables not implemented
 
 
+    def _execute_hooks(self, element):
+        """
+        Executes finalize hooks
+        """
+        for hook in self.finalize_hooks:
+            try:
+                hook(self, element)
+            except Exception as e:
+                self.warning("Plotting hook %r could not be applied:\n\n %s" % (hook, e))
+
+
     def get_data(self, element, ranges=None, empty=False):
         dims = element.dimensions()
         data = {d: np.array([]) if empty else element.dimension_values(d)
@@ -59,6 +75,7 @@ def initialize_plot(self, ranges=None, plot=None, plots=None, source=None):
                           width=self.width, **properties)
         self.handles['plot'] = table
         self.handles['glyph_renderer'] = table
+        self._execute_hooks(element)
         self.drawn = True
 
         return table