Class: Acrofill::Appearance

Inherits:
Object
  • Object
show all
Defined in:
lib/acrofill/appearance.rb

Overview

Builds the /AP /N appearance stream (a Form XObject) for a filled text-field widget, honouring the field's /DA string and /Q alignment.

Constant Summary collapse

PADDING = 
2.0
ASCENT =

Helvetica cap-height-ish ascent, em fractions

0.718
DESCENT = 
0.207
COLOR_OP_ARITY =

Colour-setting operators allowed in a /DA string, and their operand counts.

{ 'g' => 1, 'rg' => 3, 'k' => 4 }.freeze

Instance Method Summary collapse

Constructor Details

#initialize(doc, acroform) ⇒ Appearance

Returns a new instance of Appearance.



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# File 'lib/acrofill/appearance.rb', line 13

def initialize(doc, acroform)
  @doc = doc
  @acroform = acroform
end

Instance Method Details

#build(field_node, widget, value, multiline: false) ⇒ Object

Returns a Reference to the new appearance XObject, or nil when the widget geometry is unusable.



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# File 'lib/acrofill/appearance.rb', line 20

def build(field_node, widget, value, multiline: false)
  rect = normalized_rect(widget[:Rect] || @doc.inherited_value(field_node, :Rect))
  return nil unless rect

  width = rect[2] - rect[0]
  height = rect[3] - rect[1]
  return nil if width <= 0 || height <= 0

  font_name, size, color_ops = parse_da(field_node)
  base_font = base_font_for(font_name)
  align = alignment(field_node)

  body =
    if multiline
      size = 12.0 if size <= 0
      size = size.clamp(2.0, 144.0)
      multiline_body(value, base_font, size, width, height, align)
    else
      text = printable_text(value)
      size = [height * 0.66, 12.0].min if size.zero?
      size = shrink_to_fit(text, base_font, size, width)
      # Vertically center the ascent box, matching pdftk's baseline
      # placement exactly: ty = (h - ascent*size) / 2.
      ty = [(height - (size * ASCENT)) / 2.0, size * DESCENT].max
      "#{fmt(line_x(text, base_font, size, width, align))} #{fmt(ty)} Td\n" \
        "(#{escape_literal(text)}) Tj\n"
    end

  content = +"/Tx BMC\nq\nBT\n"
  content << "#{color_ops}\n" unless color_ops.empty?
  content << "/#{font_name} #{fmt(size)} Tf\n"
  content << body
  content << "ET\nQ\nEMC\n"

  dict = {
    Type: :XObject,
    Subtype: :Form,
    FormType: 1,
    BBox: [0, 0, width, height],
    Resources: { Font: { font_name.to_sym => font_ref(font_name) } }
  }
  @doc.add(StreamObject.new(dict, content.b))
end