Fixes zero division when there are no lines to plot (only one revision in range)

bench/bench_graph_svg.py

 '''
 Created on May 16, 2011
 
 @author: bungeman
 '''
 import bench_util
 import getopt
 import httplib
 import itertools
 import json
@@ skipping 791 matching lines @@
         pic_width = max(rev_width*3
                       , pic_height * (float(rev_width) / time_height))
     
     return (pic_width, pic_height)
 
 def output_svg(lines, regressions, requested_width, requested_height):
     """Outputs an svg view of the data."""
     
     (global_min_x, _), (global_max_x, global_max_y) = bounds(lines)
     max_up_slope, min_down_slope = bounds_slope(regressions)
-    
+
     #output
     global_min_y = 0
     x = global_min_x
     y = global_min_y
     w = global_max_x - global_min_x
     h = global_max_y - global_min_y
     font_size = 16
     line_width = 2
-    
+
+    # If there is nothing to see, don't try to draw anything.
+    if w == 0 or h == 0:
+        return
+
     pic_width, pic_height = compute_size(requested_width, requested_height
                                        , w, h)
     
     def cw(w1):
         """Converts a revision difference to display width."""
         return (pic_width / float(w)) * w1
     def cx(x):
         """Converts a revision to a horizontal display position."""
         return cw(x - global_min_x)
 
@@ skipping 202 matching lines @@
     print '<a id="rev_link" xlink:href="" target="_top">'
     print '<text id="revision" x="0" y=%s style="' % qa(font_size*2)
     print 'font-size: %s; ' % qe(font_size)
     print 'stroke: #0000dd; text-decoration: underline; '
     print '"> </text></a>'
 
     print '</svg>'
 
 if __name__ == "__main__":
     main()