Row spans in multi-row table header are lost after page break

[dmeranda]

If you render a table that has a header of more than one row, say :header=>2, any rowspans within that header will not be preserved when re-drawing that header on the second and following pages. It is as if the :rowspan property gets reset to 1.

Also, it might be nice to automatically infer the number of header rows when :header is passed as true, based on any rowspans.

Consider this simple example with a two-row header which does not render the second page correctly (with Prawn 1.0.0):

require 'prawn'

pdf = Prawn::Document.generate("sample.pdf") do |pdf|
  rows = [ [{:content=>"The\nNumber", :rowspan=>2}, {:content=>"Prefixed", :colspan=>2} ],
           ["A's", "B's"] ]

  (1..50).each do |n|
    rows.push( ["#{n}", "A#{n}", "B#{n}"] )
  end

  pdf.table( rows, :header=>2 ) do
    row(0..1).style :background_color=>"FFFFCC"
  end
end

[practicingruby]

@hbrandl: Please investigate

[hbrandl]

Assigned to myself. I'll look into this issue.
I'll be a lot faster if anyone can provide a failing test case for it.

[dmeranda]

The initial bug report contains the complete source to a simple failing test case.

[hbrandl]

I was thinking of an rspec test but nevermind, I found the time to create one.

  describe "headers should allow for rowspan" do 
    it "should remember rowspans accross multiple pages", :unresolved, :issue => 721 do 
      pdf = Prawn::Document.new({:page_size => "A4", :page_layout => :portrait})
      rows = [ [{:content=>"The\nNumber", :rowspan=>2}, {:content=>"Prefixed", :colspan=>2} ],
           ["A's", "B's"] ]

      (1..50).each do |n|
        rows.push( ["#{n}", "A#{n}", "B#{n}"] )
      end

      pdf.table( rows, :header=>2 ) do
         row(0..1).style :background_color=>"FFFFCC"
      end

      #ensure that the header on page 1 is identical to the header on page 0
      output = PDF::Inspector::Page.analyze(pdf.render)
      output.pages[0][:strings][0..4].should == output.pages[1][:strings][0..4]
    end
  end

I'll keep you posted.

[hbrandl]

Fixed in branch issue_721. @dmeranda can you confirm this?

@sandal Once @dmeranda has confirmed the fix, pull request #723 should be ready to merge.

[dmeranda]

@hbrandl Yes, I've verified this patch works in the real application where I had detected this bug, and which is more complicated than the very simple test case I made for this bug report.

The Prawn manual should probably be updated to note that the :header option to the table can be a number-of-rows, and not just true or false.

Also, how easy would it be to automatically determine the number of header rows, based on any rowspans within it, if :header is passed as true rather than a specific number?