provide a better default for dispBlanksAs and allow it to be configured

3 files changed, 38 insertions, 1 deletions

diff --git a/lib/axlsx/drawing/chart.rb b/lib/axlsx/drawing/chart.rb
index 79019a0a..1da3a253 100644
--- a/lib/axlsx/drawing/chart.rb
+++ b/lib/axlsx/drawing/chart.rb
@@ -20,6 +20,7 @@ module Axlsx
       @graphic_frame.anchor.drawing.worksheet.workbook.charts << self
       @series = SimpleTypedList.new Series
       @show_legend = true
+      @display_blanks_as = :gap
       @series_type = Series
       @title = Title.new
       parse_options options
@@ -70,6 +71,15 @@ module Axlsx
     # @return [Boolean]
     attr_reader :show_legend
 
+    # How to display blank values
+    # Options are
+    # * gap:  Display nothing
+    # * span: Not sure what this does
+    # * zero: Display as if the value were zero, not blank
+    # @return [Symbol]
+    # Default :gap (although this really should vary by chart type and grouping)
+    attr_reader :display_blanks_as
+
     # returns a relationship object for the chart
     # @return [Axlsx::Relationship]
     def relationship
@@ -105,6 +115,12 @@ module Axlsx
     # @return [Boolean]
     def show_legend=(v) Axlsx::validate_boolean(v); @show_legend = v; end
 
+    # How to display blank values
+    # @see display_blanks_as
+    # @param [Symbol] v
+    # @return [Symbol]
+    def display_blanks_as=(v) Axlsx::validate_display_blanks_as(v); @display_blanks_as = v; end
+
     # The style for the chart.
     # see ECMA Part 1 §21.2.2.196
     # @param [Integer] v must be between 1 and 48
@@ -157,7 +173,7 @@ module Axlsx
         str << '</c:legend>'
       end
       str << '<c:plotVisOnly val="1"/>'
-      str << '<c:dispBlanksAs val="zero"/>'
+      str << '<c:dispBlanksAs val="' << display_blanks_as.to_s << '"/>'
       str << '<c:showDLblsOverMax val="1"/>'
       str << '</c:chart>'
       str << '<c:printSettings>'
diff --git a/lib/axlsx/util/validators.rb b/lib/axlsx/util/validators.rb
index 739a4de2..a161f0d9 100644
--- a/lib/axlsx/util/validators.rb
+++ b/lib/axlsx/util/validators.rb
@@ -290,4 +290,11 @@ module Axlsx
   def self.validate_split_state_type(v)
     RestrictionValidator.validate :split_state_type, [:frozen, :frozen_split, :split], v
   end
+
+  # Requires that the value is a valid "display blanks as" type.
+  # valid types must be one of gap, span, zero
+  # @param [Any] v The value validated
+  def self.validate_display_blanks_as(v)
+    RestrictionValidator.validate :display_blanks_as, [:gap, :span, :zero], v
+  end
 end
diff --git a/test/drawing/tc_chart.rb b/test/drawing/tc_chart.rb
index 03e4fd6f..751d2ae4 100644
--- a/test/drawing/tc_chart.rb
+++ b/test/drawing/tc_chart.rb
@@ -45,6 +45,14 @@ class TestChart < Test::Unit::TestCase
     assert_equal(false, @chart.vary_colors)
   end
 
+  def test_display_blanks_as
+    assert_equal(:gap, @chart.display_blanks_as, "default is not :gap")
+    assert_raise(ArgumentError, "did not validate possible values") { @chart.display_blanks_as = :hole }
+    assert_nothing_raised { @chart.display_blanks_as = :zero }
+    assert_nothing_raised { @chart.display_blanks_as = :span }
+    assert_equal(:span, @chart.display_blanks_as)
+  end
+
   def test_start_at
     @chart.start_at 15, 25
     assert_equal(@chart.graphic_frame.anchor.from.col, 15)
@@ -94,4 +102,10 @@ class TestChart < Test::Unit::TestCase
     assert(errors.empty?, "error free validation")
   end
 
+  def test_to_xml_string_for_display_blanks_as
+    schema = Nokogiri::XML::Schema(File.open(Axlsx::DRAWING_XSD))
+    @chart.display_blanks_as = :span
+    doc = Nokogiri::XML(@chart.to_xml_string)
+    assert_equal("span", doc.xpath("//c:dispBlanksAs").attr("val").value, "did not use the display_blanks_as configuration")
+  end
 end