module Prawn::Document::Internals

This module exposes a few low-level PDF features for those who want to extend Prawn's core functionality. If you are not comfortable with low level PDF functionality as defined by Adobe's specification, chances are you won't need anything you find here.

Public Instance Methods

add_content(str) click to toggle source

Appends a raw string to the current page content.

# Raw line drawing example:           
x1,y1,x2,y2 = 100,500,300,550
pdf.add_content("%.3f %.3f m" % [ x1, y1 ])  # move 
pdf.add_content("%.3f %.3f l" % [ x2, y2 ])  # draw path
pdf.add_content("S") # stroke
# File lib/prawn/document/internals.rb, line 55
def add_content(str)
  save_graphics_state if graphic_state.nil?
  state.page.content << str << "\n"
end
before_render(&block) click to toggle source

Defines a block to be called just before the document is rendered.

# File lib/prawn/document/internals.rb, line 76
def before_render(&block)
  state.before_render_callbacks << block
end
deref(obj) click to toggle source

At any stage in the object tree an object can be replaced with an indirect reference. To get access to the object safely, regardless of if it's hidden behind a Prawn::Reference, wrap it in deref().

# File lib/prawn/document/internals.rb, line 43
def deref(obj)
  obj.is_a?(Prawn::Core::Reference) ? obj.data : obj
end
names() click to toggle source

The Name dictionary (PDF spec 3.6.3) for this document. It is lazily initialized, so that documents that do not need a name dictionary do not incur the additional overhead.

# File lib/prawn/document/internals.rb, line 64
def names
  state.store.root.data[:Names] ||= ref!(:Type => :Names)
end
names?() click to toggle source

Returns true if the Names dictionary is in use for this document.

# File lib/prawn/document/internals.rb, line 70
def names?
  state.store.root.data[:Names]
end
on_page_create(&block) click to toggle source

Defines a block to be called just before a new page is started.

# File lib/prawn/document/internals.rb, line 82
def on_page_create(&block)
   if block_given?
      state.on_page_create_callback = block
   else
      state.on_page_create_callback = nil
   end
end
ref(data) click to toggle source

Creates a new Prawn::Reference and adds it to the Document's object list. The data argument is anything that Prawn::PdfObject() can convert.

Returns the identifier which points to the reference in the ObjectStore

# File lib/prawn/document/internals.rb, line 23
def ref(data)
  ref!(data).identifier
end
ref!(data) click to toggle source

Like ref, but returns the actual reference instead of its identifier.

While you can use this to build up nested references within the object tree, it is recommended to persist only identifiers, and them provide helper methods to look up the actual references in the ObjectStore if needed. If you take this approach, Prawn::Document::Snapshot will probably work with your extension

# File lib/prawn/document/internals.rb, line 35
def ref!(data)
  state.store.ref(data)
end

Private Instance Methods

finalize_all_page_contents() click to toggle source
# File lib/prawn/document/internals.rb, line 105
def finalize_all_page_contents
  (1..page_count).each do |i|
    go_to_page i
    repeaters.each { |r| r.run(i) }
    while graphic_stack.present?
      restore_graphics_state
    end
    state.page.finalize
  end
end
fresh_content_streams(options={}) click to toggle source

adds a new, empty content stream to each page. Used in templating so that imported content streams can be left pristine

# File lib/prawn/document/internals.rb, line 95
def fresh_content_streams(options={})
  (1..page_count).each do |i|
    go_to_page i
    state.page.new_content_stream
    apply_margin_options(options)
    generate_margin_box
    use_graphic_settings(options[:template])
  end
end
min_version(min) click to toggle source

raise the PDF version of the file we're going to generate. A private method, designed for internal use when the user adds a feature to their document that requires a particular version.

# File lib/prawn/document/internals.rb, line 120
def min_version(min)
  state.version = min if min > state.version
end
render_body(output) click to toggle source

Write out the PDF Body, as per spec 3.4.2

# File lib/prawn/document/internals.rb, line 138
def render_body(output)
  state.render_body(output)
end
render_header(output) click to toggle source

Write out the PDF Header, as per spec 3.4.1

# File lib/prawn/document/internals.rb, line 126
def render_header(output)
  state.before_render_actions(self)

  # pdf version
  output << "%PDF-#{state.version}\n"

  # 4 binary chars, as recommended by the spec
  output << "%\xFF\xFF\xFF\xFF\n"
end
render_trailer(output) click to toggle source

Write out the PDF Trailer, as per spec 3.4.4

# File lib/prawn/document/internals.rb, line 157
def render_trailer(output)
  trailer_hash = {:Size => state.store.size + 1, 
                  :Root => state.store.root,
                  :Info => state.store.info}
  trailer_hash.merge!(state.trailer) if state.trailer

  output << "trailer\n"
  output << Prawn::Core::PdfObject(trailer_hash) << "\n"
  output << "startxref\n" 
  output << @xref_offset << "\n"
  output << "%%EOF" << "\n"
end
render_xref(output) click to toggle source

Write out the PDF Cross Reference Table, as per spec 3.4.3

# File lib/prawn/document/internals.rb, line 144
def render_xref(output)
  @xref_offset = output.size
  output << "xref\n"
  output << "0 #{state.store.size + 1}\n"
  output << "0000000000 65535 f \n"
  state.store.each do |ref|
    output.printf("%010d", ref.offset)
    output << " 00000 n \n"
  end
end