Fix negative and histogram

demo/moulinrouge/tests.py

@@ -353,11 +353,11 @@ def get_test_routes(app):
 
     @app.route('/test/bar/position')
     def test_bar_print_values_position():
-        bar = HorizontalBar(print_values=True, print_values_position='top',
+        bar = StackedBar(print_values=True, print_values_position='top', zero=2,
                   style=styles['default'](
                       value_font_family='googlefont:Raleway',
                       value_font_size=46))
-        bar.add('1', [-1, 2, 3])
+        bar.add('1', [1, -2, 3])
         bar.add('2', [4, -5, 6])
         bar.x_labels = [2, 4, 6]
         bar.x_labels_major = [4]
@@ -365,7 +365,7 @@ def get_test_routes(app):
 
     @app.route('/test/histogram')
     def test_histogram():
-        hist = Histogram(style=styles['neon'])
+        hist = Histogram(print_values=True, print_values_position='top', style=styles['neon'])
         hist.add('1', [
             (2, 0, 1),
             (4, 1, 3),

pygal/graph/bar.py

@@ -67,21 +67,25 @@ class Bar(Graph):
         x_center, y_center = transpose((x + width / 2, y + height / 2))
         x_top, y_top = transpose((x + width, y + height))
         x_bottom, y_bottom = transpose((x, y))
-        sign = -1 if height < self.zero else 1
+        if self._dual:
+            v = serie.values[i][0]
+        else:
+            v = serie.values[i]
+        sign = -1 if v < self.zero else 1
         self._tooltip_data(
             parent, val, x_center, y_center, "centered",
             self._get_x_label(i))
 
         if self.print_values_position == 'top':
             if self.horizontal:
-                x = x_bottom - sign * self.style.value_font_size / 2
+                x = x_bottom + sign * self.style.value_font_size / 2
                 y = y_center
             else:
                 x = x_center
                 y = y_bottom - sign * self.style.value_font_size / 2
         elif self.print_values_position == 'bottom':
             if self.horizontal:
-                x = x_top - sign * self.style.value_font_size / 2
+                x = x_top + sign * self.style.value_font_size / 2
                 y = y_center
             else:
                 x = x_center

pygal/graph/histogram.py

@@ -33,6 +33,11 @@ class Histogram(Dual, Bar):
     """Histogram chart class"""
     _series_margin = 0
 
+    @cached_property
+    def _values(self):
+        """Getter for secondary series values (flattened)"""
+        return self.yvals
+
     @cached_property
     def _secondary_values(self):
         """Getter for secondary series values (flattened)"""