Add value attribute to <td> elements for CSS conditional formatting

docs/documentation/table.rst

@@ -79,3 +79,21 @@ Transposed
   line_chart.value_formatter = lambda x: '%.2f%%' % x if x is not None else '∅'
   line_chart.render_table(style=True, total=True, transpose=True)
 
+
+Value Attribute (for CSS Conditional Formatting)
+------------------------------------------------
+
+Add to each <td> element the `value` attribute with the same content of the element itself.
+This can be useful for applying CSS conditional formatting rules.
+
+.. pygal-table-code::
+
+  line_chart = pygal.Bar()
+  line_chart.title = 'Browser usage evolution (in %)'
+  line_chart.x_labels = map(str, range(2002, 2013))
+  line_chart.add('Firefox', [None, None, 0, 16.6,   25,   31, 36.4, 45.5, 46.3, 42.8, 37.1])
+  line_chart.add('Chrome',  [None, None, None, None, None, None,    0,  3.9, 10.8, 23.8, 35.3])
+  line_chart.add('IE',      [85.8, 84.6, 84.7, 74.5,   66, 58.6, 54.7, 44.8, 36.2, 26.6, 20.1])
+  line_chart.add('Others',  [14.2, 15.4, 15.3,  8.9,    9, 10.4,  8.9,  5.8,  6.7,  6.8,  7.5])
+  line_chart.value_formatter = lambda x: '%.2f%%' % x if x is not None else '∅'
+  line_chart.render_table(style=True, total=True, value_attribute=True)

pygal/table.py

@@ -28,6 +28,10 @@
 from pygal.util import template
 
 
+def _default_value_attribute_fn(value):
+    return value
+
+
 class HTML(object):
     """Lower case adapter of lxml builder"""
 
@@ -45,14 +49,21 @@ def __init__(self, chart):
         """Init the table"""
         self.chart = chart
 
-    def render(self, total=False, transpose=False, style=False):
+    def render(self, total=False, transpose=False, style=False, value_attribute=None):
         """Render the HTMTL table of the chart.
 
         `total` can be specified to include data sums
         `transpose` make labels becomes columns
         `style` include scoped style for the table
+        `value_attribute` replicate element value into `value` attribute (<td> elements)
 
         """
+        if value_attribute is True:
+            value_attribute_fn = _default_value_attribute_fn
+        elif callable(value_attribute):
+            value_attribute_fn = value_attribute
+        else:
+            value_attribute_fn = None
         self.chart.setup()
         ln = self.chart._len
         html = HTML()
@@ -138,13 +149,19 @@ def render(self, total=False, transpose=False, style=False):
         if tbody:
             parts.append(
                 html.tbody(
-                    *[html.tr(*[html.td(_(col)) for col in r]) for r in tbody]
+                    *[html.tr(*(
+                        [html.td(_(col), value=_(value_attribute_fn(col))) for col in r]
+                        if value_attribute_fn else [html.td(_(col)) for col in r]
+                    )) for r in tbody]
                 )
             )
         if tfoot:
             parts.append(
                 html.tfoot(
-                    *[html.tr(*[html.th(_(col)) for col in r]) for r in tfoot]
+                    *[html.tr(*(
+                        [html.th(_(col), value=_(value_attribute_fn(col))) for col in r]
+                        if value_attribute_fn else [html.td(_(col)) for col in r]
+                    )) for r in tfoot]
                 )
             )