Adding annotation functionality

pygal/css/graph.css

@@ -150,3 +150,15 @@
   stroke: {{ style.background }};
   stroke-width: 2px;
 }
+
+{{ id }}.annotation.center {
+    text-anchor: middle;
+}
+
+{{ id }}.annotation.right {
+    text-anchor: start;
+}
+
+{{ id }}.annotation.left {
+    text-anchor: end;
+}

pygal/graph/base.py

@@ -158,9 +158,16 @@ class BaseGraph(object):
                     elif not is_list_like(value):
                         value = (value, self.zero)
                     if self._x_adapt:
-                        value = (
-                            self._x_adapt(value[0]),
-                            self._adapt(value[1]))
+                        if len(value) == 3:
+                            value = (
+                                self._x_adapt(value[0]),
+                                self._adapt(value[1]),
+                                value[2])
+                        else:
+                            value = (
+                                self._x_adapt(value[0]),
+                                self._adapt(value[1]))
+
                     if isinstance(self, BaseMap):
                         value = (self._adapt(value[0]), value[1])
                     else:

pygal/graph/line.py

@@ -133,6 +133,24 @@ class Line(Graph):
                     y + self.style.value_font_size,
                     metadata)
 
+        serie.show_annotations = True
+        if serie.show_annotations:
+            for i, (_, _, annotation) in enumerate(serie.values):
+                x = view_values[i][0]
+                y = view_values[i][1]
+
+                shift_x = 0
+                shift_y = -7
+
+                # TODO: draw it on the left of the point if its past half way across the X axis - how to tell?
+                self.svg.node(
+                    serie_node['plot'], 'text', class_='text annotation point_annotation',
+                    x=x,
+                    y=y,
+                    dx=shift_x,
+                    dy=shift_y
+                ).text = annotation
+
         if serie.stroke:
             if self.interpolate:
                 points = serie.interpolated