Added tests for bar value labels and fix for 0 marker count

Added commify to String to make numbers look pretty
Added label_format to allow for formatting of value labels

lib/gruff/bar.rb

@@ -92,7 +92,8 @@ def draw_bars
         # Subtract half a bar width to center left if requested
         draw_label(label_center - (@center_labels_over_point ? @bar_width / 2.0 : 0.0), point_index)
         if @show_labels_for_bar_values
-          draw_value_label(left_x + (right_x - left_x)/2, conv[0]-30, @norm_data[row_index][3][point_index])
+          val = (@label_formatting || "%.2f") % @norm_data[row_index][3][point_index] 
+          draw_value_label(left_x + (right_x - left_x)/2, conv[0]-30, val.commify)
         end
       end
 

lib/gruff/base.rb

@@ -188,7 +188,11 @@ class Base
     # Output the values for the bars on a bar graph
     # Default is false
     attr_accessor :show_labels_for_bar_values
-
+    
+    # Set the number output format for labels using sprintf
+    # Default is "%.2f"
+    attr_accessor :label_formatting
+    
     # If one numerical argument is given, the graph is drawn at 4/3 ratio
     # according to the given width (800 results in 800x600, 400 gives 400x300,
     # etc.).
@@ -1105,3 +1109,10 @@ def annotate_scaled(img, width, height, x, y, text, scale)
   end
 
 end # Magick
+
+class String
+  #Taken from http://codesnippets.joyent.com/posts/show/330
+  def commify(delimiter=",")
+    return self.gsub(/(\d)(?=(\d\d\d)+(?!\d))/, "\\1#{delimiter}")
+  end
+end

test/test_bar.rb

@@ -444,6 +444,19 @@ def test_set_label_max_size_and_label_truncation_style
     g.write("test/output/bar_set_trailing_dots_trunc.png")
   end
 
+  
+  def test_bar_value_labels
+    g = setup_basic_graph
+    g.show_labels_for_bar_values = true
+    g.write("test/output/bar_value_labels.png")
+  end
+  
+  def test_zero_marker_count
+    g = setup_basic_graph
+    g.marker_count = 0
+    g.write("test/output/bar_zero_marker_count.png")
+  end
+  
   protected
 
   def setup_basic_graph(size=800)