Implement #311: feature - bar max width

lib/morris.bar.coffee

@@ -92,7 +92,9 @@ class Morris.Bar extends Morris.Grid
     groupWidth = @width / @options.data.length
     numBars = if @options.stacked? then 1 else @options.ykeys.length
     barWidth = (groupWidth * @options.barSizeRatio - @options.barGap * (numBars - 1)) / numBars
-    leftPadding = groupWidth * (1 - @options.barSizeRatio) / 2
+    barWidth = Math.min(barWidth, @options.barSize) if @options.barSize
+    spaceLeft = groupWidth - barWidth * numBars - @options.barGap * (numBars - 1)
+    leftPadding = spaceLeft / 2
     zeroPos = if @ymin <= 0 and @ymax >= 0 then @transY(0) else null
     @bars = for row, idx in @data
       lastTop = 0

spec/lib/bar/bar_spec.coffee

@@ -68,3 +68,31 @@ describe 'Morris.Bar', ->
         chart = Morris.Bar $.extend {}, defaults,
             barRadius: [300, 300, 0, 0]
         $('#graph').find("rect").size().should.equal 4
+
+  describe 'barSize option', ->
+    describe 'svg attributes', ->
+      defaults =
+        element: 'graph'
+        barSize: 20
+        data: [
+          {x: '2011 Q1', y: 3, z: 2, a: 3}
+          {x: '2011 Q2', y: 2, z: null, a: 1}
+          {x: '2011 Q3', y: 0, z: 2, a: 4}
+          {x: '2011 Q4', y: 2, z: 4, a: 3}
+        ],
+        xkey: 'x'
+        ykeys: ['y', 'z', 'a']
+        labels: ['Y', 'Z', 'A']
+
+      it 'should calc the width if too narrow for barSize', ->
+        $('#graph').width('200px')
+        chart = Morris.Bar $.extend {}, defaults
+        $('#graph').find("rect").filter((i) ->
+          parseFloat($(@).attr('width'), 10) < 10
+        ).size().should.equal 11
+
+      it 'should set width to @options.barSize if possible', ->
+        chart = Morris.Bar $.extend {}, defaults
+        $('#graph').find("rect[width='#{defaults.barSize}']").size().should.equal 11
+
+