move Square_element.size to painter, and allow for squares to determine their own size

src/painter.py

@@ -43,6 +43,9 @@ class Painter(Widget):
         # modifiers
         self.modifiers=[]
 
+        # base size for all particles
+        self.base_size=50
+
         # init Widget
         super(Painter,self).__init__(**kwargs)
 
@@ -75,13 +78,13 @@ class Painter(Widget):
 
     # convert logical coordinates (normalized and centered) to the ones that are plotted
     def pos_tocoord_x(self,x):
-        return self.width/2+x*Square_element.size
+        return self.width/2+x*self.base_size
     def pos_tocoord_y(self,y):
-        return self.height/2+y*Square_element.size
+        return self.height/2+y*self.base_size
     def coord_topos_x(self,x):
-        return (x-self.width/2)/Square_element.size
+        return (x-self.width/2)/self.base_size
     def coord_topos_y(self,y):
-        return (y-self.height/2)/Square_element.size
+        return (y-self.height/2)/self.base_size
         
 
 
@@ -176,10 +179,10 @@ class Painter(Widget):
             # zoom
             elif text=="+":
                 # increment by 10%
-                self.set_zoom(Square_element.size/50*1.1)
+                self.set_zoom(self.base_size/50*1.1)
             elif text=="-":
                 # decrease by 10%
-                self.set_zoom(Square_element.size/50*0.9)
+                self.set_zoom(self.base_size/50*0.9)
             elif text=="=":
                 # reset
                 self.set_zoom(1)
@@ -557,7 +560,7 @@ class Painter(Widget):
 
     # set zoom level
     def set_zoom(self,level):
-        Square_element.size=level*50
+        self.base_size=level*50
         self.draw()