Index: ChangeLog
===================================================================
--- ChangeLog	(revision 1956)
+++ ChangeLog	(working copy)
@@ -1,3 +1,8 @@
+2010-07-29  Georg von Hippel <gmv22@cantab.net>
+
+	* Fixed bug reported by Jesse Dunietz; each diagram now gets its
+	own canvas, which can be set in the constructor.
+
 2010-01-22  Georg von Hippel <gmv22@cantab.net>
 
 	* Added support for helicity-style (=>) arrows. This still needs work.
Index: pyfeyn/deco.py
===================================================================
--- pyfeyn/deco.py	(revision 1956)
+++ pyfeyn/deco.py	(working copy)
@@ -117,7 +117,7 @@
             normal = normal.transformed(pyx.trafo.rotate(180, x, y))
             nx, ny = normal.atend()
         if config.getOptions().VDEBUG:
-            FeynDiagram.currentCanvas.stroke(normal)
+            FeynDiagram.currentDiagram.currentCanvas.stroke(normal)
 
         ## Displace the arrow by this normal vector
         endx, endy = endx + (nx-x), endy + (ny-y)
@@ -290,7 +290,7 @@
             normal = normal.transformed(pyx.trafo.rotate(180, x, y)) 
             nx, ny = normal.atend()
         if config.getOptions().VDEBUG:
-            FeynDiagram.currentCanvas.stroke(normal)
+            FeynDiagram.currentDiagram.currentCanvas.stroke(normal)
 
         ## Displace the label by this normal vector
         x, y = nx, ny
Index: pyfeyn/lines.py
===================================================================
--- pyfeyn/lines.py	(revision 1956)
+++ pyfeyn/lines.py	(working copy)
@@ -130,14 +130,14 @@
             ny *= -1
         arcpoint = Point(middle.x() + amount * nx, middle.y() + amount * ny)
         if config.getOptions().VDEBUG:
-            FeynDiagram.currentCanvas.stroke(
+            FeynDiagram.currenDiagram.currentCanvas.stroke(
                 pyx.path.line(middle.x(), middle.y(), arcpoint.x(),
                               arcpoint.y()), [color.rgb.blue] )
         self.arcThru(arcpoint)
         if config.getOptions().DEBUG:
             print self.getVisiblePath()
         if config.getOptions().VDEBUG:
-            FeynDiagram.currentCanvas.stroke(self.getVisiblePath(), [color.rgb.blue])
+            FeynDiagram.currenDiagram.currentCanvas.stroke(self.getVisiblePath(), [color.rgb.blue])
         return self
 
 
@@ -188,7 +188,7 @@
             circle = pyx.path.circle(*cargs)
             line = pyx.path.line( self.p1.x(), self.p1.y(), arccenter.x(), arccenter.y())
             if config.getOptions().VDEBUG:
-                FeynDiagram.currentCanvas.stroke(line, [color.rgb.green])
+                FeynDiagram.currenDiagram.currentCanvas.stroke(line, [color.rgb.green])
             ass, bs = circle.intersect(line)
             subpaths = circle.split(ass[0])
             cpath = subpaths[0]
@@ -274,7 +274,7 @@
         p2path = self.p2.getPath()
         vispath = self.getPath()
         if config.getOptions().VDEBUG:
-            FeynDiagram.currentCanvas.stroke(vispath, [color.rgb.green])
+            FeynDiagram.currenDiagram.currentCanvas.stroke(vispath, [color.rgb.green])
         if p1path:
             ass, bs = p1path.intersect(vispath)
             for b in bs:
@@ -288,11 +288,11 @@
                             math.fabs(pyx.unit.tocm(x.arclen() - y.arclen()))) )
                     vispath = subpaths[-1]
                     if config.getOptions().VDEBUG:
-                        FeynDiagram.currentCanvas.stroke(subpaths[0], [color.rgb.blue])
+                        FeynDiagram.currenDiagram.currentCanvas.stroke(subpaths[0], [color.rgb.blue])
                 if config.getOptions().VDEBUG:
                     for a in ass:
                         ix, iy = p1path.at(a)
-                        FeynDiagram.currentCanvas.fill(pyx.path.circle(ix, iy, 0.05),
+                        FeynDiagram.currenDiagram.currentCanvas.fill(pyx.path.circle(ix, iy, 0.05),
                                                        [color.rgb.green])
         if p2path: 
             ass, bs = p2path.intersect(vispath)
@@ -307,14 +307,14 @@
                             math.fabs(pyx.unit.tocm(x.arclen() - y.arclen()))) )
                     vispath = subpaths[-1]
                     if config.getOptions().VDEBUG:
-                        FeynDiagram.currentCanvas.stroke(subpaths[0], [color.rgb.red])
+                        FeynDiagram.currenDiagram.currentCanvas.stroke(subpaths[0], [color.rgb.red])
                 if config.getOptions().VDEBUG:
                     for a in ass:
                         ix, iy = p2path.at(a)
-                        FeynDiagram.currentCanvas.fill(pyx.path.circle(ix, iy, 0.05),
+                        FeynDiagram.currenDiagram.currentCanvas.fill(pyx.path.circle(ix, iy, 0.05),
                                                        [color.rgb.blue])
         if config.getOptions().VDEBUG:
-            FeynDiagram.currentCanvas.stroke(vispath, [color.rgb.red])
+            FeynDiagram.currenDiagram.currentCanvas.stroke(vispath, [color.rgb.red])
         #return pyx.path.circle(-2,-1,0.2)
         return vispath
 
Index: pyfeyn/diagrams.py
===================================================================
--- pyfeyn/diagrams.py	(revision 1956)
+++ pyfeyn/diagrams.py	(working copy)
@@ -8,15 +8,17 @@
 class FeynDiagram:
     """The main PyFeyn diagram class."""    
     currentDiagram = None
-    currentCanvas = pyx.canvas.canvas()
 
-    def __init__(self, objects=None):
+    def __init__(self, objects=None, canvas=None):
         """Objects for holding a set of Feynman diagram components."""
         self.__objs = objects
         if self.__objs is None:
             self.__objs = []
         self.highestautolayer = 0
-        FeynDiagram.currentCanvas = pyx.canvas.canvas()
+        if canvas is None:
+           self.currentCanvas = pyx.canvas.canvas()
+        else:
+           self.currentCanvas = canvas
         FeynDiagram.currentDiagram = self
 
 
@@ -56,9 +58,9 @@
         for obj in drawingobjs:
             if config.getOptions().DEBUG:
                 print "Depth = ", obj.getDepth()
-            obj.draw(FeynDiagram.currentCanvas)
+            obj.draw(self.currentCanvas)
 
-        return FeynDiagram.currentCanvas
+        return self.currentCanvas
 
 
     def draw(self, outfile):