diff --git a/SketchWidget.py b/SketchWidget.py
index 8807aa4..17e94f5 100644
--- a/SketchWidget.py
+++ b/SketchWidget.py
@@ -19,6 +19,7 @@ class SketchWidget:
         self.drawingShape = None
         self.drawingConstraints = []
         self.mode = ''
+        self.snap_points = {} # keyed by (shape, ptNum)
 
         # Configuration parameters
         self.line_width = 1.5
@@ -31,6 +32,7 @@ class SketchWidget:
         self.constraint_color = (0.8, 1.0, 0.0, 1.0)
         self.snap_angle = 10
         self.hv_snap_dist = 10
+        self.snap_dist = 4
 
         try:
             # try double-buffered
@@ -99,6 +101,8 @@ class SketchWidget:
 
         gldrawable.gl_end()
 
+        self.update_snap_points()
+
         return True
 
     def draw(self, glarea, event):
@@ -234,6 +238,7 @@ class SketchWidget:
     def button_release_event(self, widget, event, data = None):
         if event.button == 2:
             self.panning = False
+            self.update_snap_points()
 
     def motion_event(self, widget, event, data = None):
         if self.panning:
@@ -258,6 +263,7 @@ class SketchWidget:
             self.view_center = (zoom_pt[0] - off_x / self.zoom_factor,
                     zoom_pt[1] - off_y / self.zoom_factor)
             self.view_width /= self.zoom_factor
+            self.update_snap_points()
             self.queue_redraw()
         elif event.direction == gtk.gdk.SCROLL_DOWN:
             zoom_pt = self.screenPtToPt((event.x,
@@ -267,6 +273,7 @@ class SketchWidget:
             self.view_center = (zoom_pt[0] - off_x * self.zoom_factor,
                     zoom_pt[1] - off_y * self.zoom_factor)
             self.view_width *= self.zoom_factor
+            self.update_snap_points()
             self.queue_redraw()
 
     def queue_redraw(self):
@@ -424,3 +431,13 @@ class SketchWidget:
         x = pt2[0] - pt1[0]
         y = pt2[1] - pt1[1]
         return math.sqrt(x * x + y * y)
+
+    def update_snap_points(self):
+        self.snap_points = {}
+        for s in self.sketch.shapes:
+            self.add_snap_points(s)
+
+    def add_snap_points(self, shape):
+        for i in range(shape.nPts()):
+            pt = self.ptToScreenPt(shape.getPt(i))
+            self.snap_points[(shape, i)] = pt