Allow Line.points definition to be a mix of lists/tuples

Fix for issue kivy#3481
Line.points can be defined as list of lists, tuples and
coordinates (float values)
setter method modified to check each element of the argument
list and append it to self._points accordingly
Line example file /examples/canvas/line.py updated with the new
possible way of defining points

examples/canvas/lines.py

@@ -139,7 +139,7 @@ class LinePlayground(FloatLayout):
     alpha_controlline = NumericProperty(1.0)
     alpha = NumericProperty(0.5)
     close = BooleanProperty(False)
-    points = ListProperty([500, 500, 300, 300, 500, 300, 500, 400, 600, 400])
+    points = ListProperty([(500, 500), 300, 300, 500, 300, [500, 400, 600, 400]])
     points2 = ListProperty([])
     joint = OptionProperty('none', options=('round', 'miter', 'bevel', 'none'))
     cap = OptionProperty('none', options=('round', 'square', 'none'))

kivy/graphics/vertex_instructions_line.pxi

@@ -673,7 +673,14 @@ cdef class Line(VertexInstruction):
         def __get__(self):
             return self._points
         def __set__(self, points):
-            self._points = list(points)
+            import itertools
+            tmp=[]
+            for p in points:
+                if isinstance(p,(list,tuple)):
+                    tmp=tmp+list(p)
+                else:
+                    tmp.append(p)
+            self._points=tmp
             self.flag_update()
 
     property dash_length: