Generate single sketch for cover sheet instead of one for each part.

- cvr.py (outline_cad): accept sketch as argument instead of creating a
  new one
- cvr.py (outline_gnuplot): added dummy sketch argument
- cvr.py (closed_outline, open_outlineoutline, label): pass sketch
  argument

cvr.py

@@ -7,7 +7,7 @@ import shape
 # gnuplot the outline
 #
 
-def outline_gnuplot(points):
+def outline_gnuplot(sk, points):
     while len(points):
 	print points.pop(0), points.pop(0)
     print
@@ -29,10 +29,7 @@ def cad_line(sk, x0, y0, x1, y1):
     cad.add(sk, cad.getlastobj())
 
 
-def outline_cad(points):
-    cad.sketch()
-    sk = cad.getlastobj()
-
+def outline_cad(sk, points):
     last_x = points.pop(0)
     last_y = points.pop(0)
     while len(points):
@@ -46,15 +43,15 @@ def outline_cad(points):
     return sk
 
 
-def closed_outline(*args):
+def closed_outline(sk, *args):
     l = list(args)
     l.append(args[0])
     l.append(args[1])
-    do(l)
+    do(sk, l)
 
 
-def open_outline(*args):
-    do(list(args))
+def open_outline(sk, *args):
+    do(sk, list(args))
 
 
 def line(*args):
@@ -97,8 +94,8 @@ def line(*args):
 #
 
 
-def outline():
-    closed_outline(
+def outline(sk):
+    closed_outline(sk,
       # counterweight corners: (16, 46) and (15, 60)
       13, 46,
       # (15, 69.5)
@@ -123,12 +120,12 @@ def outline():
       26, 46)
 
 
-def label():
+def label(sk):
     u = 2
     x = 40
     y = 66
     # C
-    open_outline(
+    open_outline(sk,
       x+u, y+2*u, 
       x, y+2*u, 
       x, y, 
@@ -136,7 +133,7 @@ def label():
 
     x += u*1.6 
     # W
-    open_outline(
+    open_outline(sk,
       x, y+2*u, 
       x, y, 
       x+0.5*u, y+u, 
@@ -164,12 +161,17 @@ def rect_outline(x0, y0, z0, x1, y1, z1):
 
 if __name__ == "__main__":
     do = outline_gnuplot
+    sk = None
 else:
     import HeeksPython as cad
-    do = outline_cad
 
-outline()
-label()
+    do = outline_cad
+    cad.sketch()
+    sk = cad.getlastobj()
+
+
+outline(sk)
+label(sk)
 
 shape.rect = rect_outline
 shape.make_base()
@@ -178,7 +180,5 @@ if __name__ == "__main__":
     for e in lines:
 	gnuplot_line(*e)
 else:
-    cad.sketch()
-    sk = cad.getlastobj()
     for e in lines:
 	cad_line(sk, *e)