Add :col_max_length setting

Allows for a maximum column width to be specified for charts of type `:column` or `:stack`.

Author: grantneufeld

examples/squid/col_max_width.rb

@@ -0,0 +1,9 @@
+# By default, <code>chart</code> maximizes the width of columns.
+#
+# You can use the <code>:col_max_width</code> option to limit the maximum width of columns in the chart (measured in points; 72 points per inch).
+#
+filename = File.basename(__FILE__).gsub('.rb', '.pdf')
+Prawn::ManualBuilder::Example.generate(filename) do
+  data = {views: {2013 => 182, 2014 => 46, 2015 => 134}}
+  chart data, col_max_width: 20
+end

examples/squid/squid.rb

@@ -17,6 +17,7 @@
     p.section 'Basics' do |s|
       s.example 'basic'
       s.example 'legend'
+      s.example 'col_max_width'
     end
 
     p.section 'Chart types' do |s|

lib/squid/configuration.rb

@@ -59,6 +59,7 @@ def self.array(proc = nil)
       labels:       {as: array(boolean)},
       legend:       {as: boolean,        default: 'true'},
       line_widths:  {as: array(float)},
+      col_max_width: {as: integer,       default: '0'},
       steps:        {as: integer,        default: '4'},
       ticks:        {as: boolean,        default: 'true'},
       type:         {as: symbol,         default: 'column'},

lib/squid/graph.rb

@@ -13,11 +13,11 @@ module Squid
   class Graph
     extend Settings
     has_settings :baseline, :border, :chart, :colors, :every, :formats, :height
-    has_settings :legend, :line_widths, :steps, :ticks, :type, :labels
+    has_settings :legend, :line_widths, :col_max_width, :steps, :ticks, :type, :labels
 
     def initialize(document, data = {}, settings = {})
       @data, @settings = data, settings
-      @plot = Plotter.new document, bottom: bottom
+      @plot = Plotter.new document, bottom: bottom, col_max_width: settings[:col_max_width]
       @plot.paddings = {left: left.width, right: right.width} if @data.any?
     end
 

lib/squid/plotter.rb

@@ -7,9 +7,10 @@ module Squid
   class Plotter
     attr_accessor :paddings
     # @param [Prawn::Document] a PDF document to wrap in a Plotter instance.
-    def initialize(pdf, bottom:)
+    def initialize(pdf, bottom:, col_max_width: 0)
       @pdf = pdf
       @bottom = bottom
+      @col_max_width = col_max_width || 0
     end
 
     # Draws a bounding box of the given height, rendering the block inside it.
@@ -96,14 +97,23 @@ def lines(series, options = {})
     def stacks(series, options = {})
       items(series, options.merge(fill: true)) do |point, w, i, padding|
         x, y = point.index*w + padding + left, point.y + @bottom
-        @pdf.fill_rectangle [x, y], w - 2*padding, point.height
+        w -= 2 * padding
+        if @col_max_width > 0 && @col_max_width < w
+          x += (w - @col_max_width) / 2
+          w = @col_max_width
+        end
+        @pdf.fill_rectangle [x, y], w, point.height
       end
     end
 
     def columns(series, options = {})
       items(series, options.merge(fill: true, count: series.size)) do |point, w, i, padding|
         item_w = (w - 2 * padding)/ series.size
         x, y = point.index*w + padding + left + i*item_w, point.y + @bottom
+        if @col_max_width > 0 && @col_max_width < item_w
+          x += (item_w - @col_max_width) / 2
+          item_w = @col_max_width
+        end
         @pdf.fill_rectangle [x, y], item_w, point.height
       end
     end

spec/configuration_spec.rb

@@ -28,6 +28,7 @@
   it_behaves_like 'a configurable setting', method: 'labels',      env: 'SQUID_LABELS',      default: [],         sample_value: sample_true
   it_behaves_like 'a configurable setting', method: 'legend',      env: 'SQUID_LEGEND',      default: true,       sample_value: sample_false
   it_behaves_like 'a configurable setting', method: 'line_widths', env: 'SQUID_LINE_WIDTHS', default: []   ,      sample_value: '4'
+  it_behaves_like 'a configurable setting', method: 'col_max_width', env: 'SQUID_COL_MAX_WIDTH', default: 0,      sample_value: '20'
   it_behaves_like 'a configurable setting', method: 'steps',       env: 'SQUID_STEPS',       default: 4,          sample_value: '0'
   it_behaves_like 'a configurable setting', method: 'ticks',       env: 'SQUID_TICKS',       default: true,       sample_value: sample_false
   it_behaves_like 'a configurable setting', method: 'type',        env: 'SQUID_TYPE',        default: :column,    sample_value: 'line'

spec/squid_spec.rb

@@ -55,6 +55,16 @@
       end
     end
 
+    context 'given the :col_max_width is set to a value greater than zero' do
+      let(:maximum) { 20 }
+      let(:settings) { options.merge col_max_width: maximum }
+
+      it 'creates the columns within the specified width' do
+        widths = rectangles_of(chart).map{ |r| r[:width] }
+        expect(widths[0]).to eq maximum
+      end
+    end
+
     context 'given the series has nil values' do
       let(:values) { {2013 => -50, 2014 => nil, 2015 => 20} }
 
@@ -144,6 +154,16 @@
       it 'includes as many stacks as the number of values' do
         expect(rectangles_of(chart).map{|r| r[:point].first}.uniq.size).to be 3
       end
+
+      context 'given the :col_max_width is set to a value greater than zero' do
+        let(:maximum) { 20 }
+        let(:settings) { options.merge type: :stack, col_max_width: maximum }
+
+        it 'creates the columns within the specified width' do
+          widths = rectangles_of(chart).map{ |r| r[:width] }
+          expect(widths[0]).to eq maximum
+        end
+      end
     end
 
     context 'given multiple options are provided' do