Allow to inverse y axis, Fixes Kozea#24

demo/moulinrouge/tests.py

@@ -379,7 +379,6 @@ class LolConfig(Config):
 
     @app.route('/test/dateline')
     def test_dateline():
-        from datetime import date
         datey = DateLine(show_dots=False)
         datey.add('1', [
             (datetime(2013, 1, 2), 300),
@@ -427,8 +426,8 @@ def test_timexy():
             (time(21, 2, 29), 10),
             (time(12, 30, 59), 7)
         ])
-        datey.add('2',
-            [(time(12, 12, 12), 4), (time(), 8), (time(23, 59, 59), 6)])
+        datey.add(
+            '2', [(time(12, 12, 12), 4), (time(), 8), (time(23, 59, 59), 6)])
         datey.x_label_rotation = 25
         return datey.render_response()
 
@@ -624,4 +623,10 @@ def test_sparkline_for(chart):
         graph.legend_at_bottom = True
         return graph.render_response()
 
+    @app.route('/test/inverse_y_axis/<chart>')
+    def test_inverse_y_axis(chart):
+        graph = CHARTS_BY_NAME[chart](**dict(inverse_y_axis=True))
+        graph.add('inverse', [1, 2, 3, 12, 24, 36])
+        return graph.render_response()
+
     return list(sorted(filter(lambda x: x.startswith('test'), locals())))

pygal/config.py

@@ -446,6 +446,8 @@ class Config(CommonConfig):
         False, bool, "Misc",
         "Don't prefix css")
 
+    inverse_y_axis = Key(False, bool, "Misc", "Inverse Y axis direction")
+
 
 class SerieConfig(CommonConfig):
     """Class holding serie config values"""

pygal/graph/graph.py

@@ -24,7 +24,7 @@
 from __future__ import division
 from pygal.interpolate import INTERPOLATIONS
 from pygal.graph.base import BaseGraph
-from pygal.view import View, LogView, XYLogView
+from pygal.view import View, LogView, XYLogView, ReverseView
 from pygal.util import (
     truncate, reverse_text_len, get_texts_box, cut, rad, decorate)
 from math import sqrt, ceil, cos
@@ -58,7 +58,7 @@ def _set_view(self):
             else:
                 view_class = LogView
         else:
-            view_class = View
+            view_class = ReverseView if self.inverse_y_axis else View
 
         self.view = view_class(
             self.width - self.margin.x,
@@ -211,7 +211,9 @@ def _y_axis(self):
                 self.show_y_guides):
             self.svg.node(
                 axis, 'path',
-                d='M%f %f h%f' % (0, self.view.height, self.view.width),
+                d='M%f %f h%f' % (
+                    0, 0 if self.inverse_y_axis else self.view.height,
+                    self.view.width),
                 class_='line'
             )
 

pygal/view.py

@@ -155,6 +155,13 @@ def __call__(self, xy):
         return (self.x(x), self.y(y))
 
 
+class ReverseView(View):
+    def y(self, y):
+        if y is None:
+            return None
+        return (self.height * (y - self.box.ymin) / self.box.height)
+
+
 class HorizontalView(View):
     def __init__(self, width, height, box):
         self._force_vertical = None