prawnpdf/prawn

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lib/prawn/document/span.rb

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# frozen_string_literal: true

# span.rb : Implements text columns
#
# Copyright September 2008, Gregory Brown. All Rights Reserved.
#
# This is free software. Please see the LICENSE and COPYING files for details.

module Prawn
  class Document
    # @group Stable API

    # A span is a special purpose bounding box that allows a column of
    # elements to be positioned relative to the margin_box.
    #
    # Arguments:
    # +width+:: The width of the column in PDF points
    #
    # Options:
    # <tt>:position</tt>:: One of :left, :center, :right or an x offset
    #
    # This method is typically used for flowing a column of text from one
    # page to the next.
    #
    #  span(350, :position => :center) do
    #    text "Here's some centered text in a 350 point column. " * 100
    #  end
    #
    def span(width, options = {})
      Prawn.verify_options [:position], options
      original_position = y

      # FIXME: Any way to move this upstream?
      left_boundary =
        case options.fetch(:position, :left)
        when :left
          margin_box.absolute_left
        when :center
          margin_box.absolute_left + margin_box.width / 2.0 - width / 2.0
        when :right
          margin_box.absolute_right - width
        when Numeric
          margin_box.absolute_left + options[:position]
        else
          raise ArgumentError, 'Invalid option for :position'
        end

      # we need to bust out of whatever nested bounding boxes we're in.
      canvas do
        bounding_box(
          [
            left_boundary,
            margin_box.absolute_top
          ], width: width
        ) do
          self.y = original_position
          yield
        end
      end
    end
  end
end