Set shape from command

src/painter.py

@@ -35,6 +35,9 @@ class Painter(Widget):
         # list of particles
         self.particles=[]
 
+        # shape of particle to add next
+        self.shape=Cross
+
         # underlying lattice
         self.lattice=None
 
@@ -229,8 +232,7 @@ class Painter(Widget):
 
             # create new particle
             if touch.button=="right":
-                new=Cross(touchx,touchy)
-                #new=Disk(touchx,touchy)
+                new=self.shape(touchx,touchy)
                 # snap to lattice
                 if self.lattice!=None:
                     new.move(self.lattice.nearest_delta(new.elements[0].pos))