diff --git a/demo/simple_test.py b/demo/simple_test.py
index 6a9fa3f..4905084 100755
--- a/demo/simple_test.py
+++ b/demo/simple_test.py
@@ -46,7 +46,7 @@ hbar.x_labels = map(
 hbar.title = "Horizontal Bar test"
 # hbar.render_to_file('out-horizontalbar.svg')
 
-rng = [3, -32, 39, 12]
+rng = [30, -32, 39, 12]
 rng2 = [24, -8, 18, 12]
 rng3 = [6, 1, -10, 0]
 config = Config()
@@ -70,7 +70,9 @@ hstackedbar = HorizontalStackedBar(config)
 hstackedbar.add('@@@@@@@', rng)
 hstackedbar.add('++++++', rng2)
 hstackedbar.add('--->', rng3)
-# hstackedbar.render_to_file('out-horizontalstackedbar.svg')
+
+hstackedbar.render_to_file('out-horizontalstackedbar1.svg')
+hstackedbar.render_to_file('out-horizontalstackedbar2.svg')
 
 line = Line(Config(style=NeonStyle,
                    zero=.0001, fill=True,
diff --git a/pygal/graph/base.py b/pygal/graph/base.py
index 334100d..01fa5a5 100644
--- a/pygal/graph/base.py
+++ b/pygal/graph/base.py
@@ -15,8 +15,10 @@ class BaseGraph(object):
         self.config(**kwargs)
         self.svg = Svg(self)
         self.series = []
-        self.margin = Margin(*([20] * 4))
         self._x_labels = self._y_labels = None
+
+    def _init(self):
+        self.margin = Margin(*([20] * 4))
         self._box = Box()
 
     def __getattr__(self, attr):
@@ -149,6 +151,7 @@ class BaseGraph(object):
         return True
 
     def _render(self):
+        self._init()
         self.svg._init()
         if self._has_data():
             self._draw()
@@ -179,3 +182,12 @@ class BaseGraph(object):
     def render_to_file(self, filename):
         with open(filename, 'w') as f:
             f.write(self.render())
+
+    def render_to_png(self, filename):
+        import cairosvg
+        import StringIO
+        fakefile = StringIO.StringIO()
+        fakefile.write(self.render())
+        fakefile.seek(0)
+        cairosvg.surface.PNGSurface.convert(
+            file_obj=fakefile, write_to=filename)
diff --git a/pygal/graph/horizontal.py b/pygal/graph/horizontal.py
index 6bf23db..900487c 100644
--- a/pygal/graph/horizontal.py
+++ b/pygal/graph/horizontal.py
@@ -24,18 +24,21 @@ from pygal.graph.stackedbar import StackedBar
 class HorizontalGraph(Graph):
     """Horizontal graph"""
     def __init__(self, *args, **kwargs):
+        self.first_pass = True
         kwargs['_horizontal'] = True
         super(HorizontalGraph, self).__init__(*args, **kwargs)
 
     def _compute(self):
-        if self.x_labels:
-            self.x_labels = reversed(self.x_labels)
+        self.first_pass = False
+        if self.first_pass and self.x_labels:
+            self.x_labels = list(reversed(self.x_labels))
         super(HorizontalGraph, self)._compute()
         self._x_labels, self._y_labels = self._y_labels, self._x_labels
         self._box.swap()
         # Y axis is inverted
-        for serie in self.series:
-            serie.values = reversed(serie.values)
+        if self.first_pass:
+            for serie in self.series:
+                serie.values = list(reversed(serie.values))
 
 
 class HorizontalBar(HorizontalGraph, Bar):
diff --git a/pygal/svg.py b/pygal/svg.py
index 00c74d5..18f05d3 100644
--- a/pygal/svg.py
+++ b/pygal/svg.py
@@ -51,7 +51,7 @@ class Svg(object):
             style.text = templ.decode('utf-8')
 
     def add_script(self, js):
-        script = self.node(self.root, 'script', type='text/javascript')
+        script = self.node(self.defs, 'script', type='text/javascript')
         with open(js) as f:
             templ = template(
                 f.read(),
@@ -87,6 +87,8 @@ class Svg(object):
         return '%f %f' % xy
 
     def line(self, node, coords, close=False, **kwargs):
+        if len(coords) < 2:
+            return
         root = 'M%s L%s Z' if close else 'M%s L%s'
         origin_index = 0
         while None in coords[origin_index]:
diff --git a/pygal/test/test_graph.py b/pygal/test/test_graph.py
index 258741b..c2be88e 100644
--- a/pygal/test/test_graph.py
+++ b/pygal/test/test_graph.py
@@ -18,6 +18,20 @@
 # along with pygal. If not, see <http://www.gnu.org/licenses/>.
 import os
 from pygal import Line
+import pygal
+
+
+def test_multi_render():
+    for Chart in pygal.CHARTS:
+        chart = Chart()
+        rng = range(20)
+        if Chart == pygal.XY:
+            rng = zip(rng, rng)
+        chart.add('Serie', rng)
+        chart.add('Serie 2', list(reversed(rng)))
+        svg = chart.render()
+        for i in range(2):
+            assert svg == chart.render()
 
 
 def test_render_to_file():
@@ -31,3 +45,16 @@ def test_render_to_file():
     with open(file_name) as f:
         assert 'pygal' in f.read()
     os.remove(file_name)
+
+
+def test_render_to_png():
+    file_name = '/tmp/test_graph.png'
+    if os.path.exists(file_name):
+        os.remove(file_name)
+
+    line = Line()
+    line.add('Serie 1', [1])
+    line.render_to_png(file_name)
+    with open(file_name) as f:
+        assert f.read()
+    os.remove(file_name)
diff --git a/setup.py b/setup.py
index 9fb9059..44f058b 100644
--- a/setup.py
+++ b/setup.py
@@ -31,7 +31,7 @@ setup(
     packages=find_packages(),
     provides=['pygal'],
     scripts=["pygal_gen.py"],
-    keywords=["svg", "graph", "diagram", "plot", "histogram", "kiviat"],
+    keywords=["svg", "chart", "graph", "diagram", "plot", "histogram", "kiviat"],
     tests_require=["pytest", "pyquery", "flask"],
     package_data={'pygal': ['css/*', 'js/*']},
     install_requires=['lxml'],