# -*- encoding: utf-8; frozen_string_literal: true -*-
#
#--
# This file is part of HexaPDF.
#
# HexaPDF - A Versatile PDF Creation and Manipulation Library For Ruby
# Copyright (C) 2014-2021 Thomas Leitner
#
# HexaPDF is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License version 3 as
# published by the Free Software Foundation with the addition of the
# following permission added to Section 15 as permitted in Section 7(a):
# FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
# THOMAS LEITNER, THOMAS LEITNER DISCLAIMS THE WARRANTY OF NON
# INFRINGEMENT OF THIRD PARTY RIGHTS.
#
# HexaPDF is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public
# License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with HexaPDF. If not, see <http://www.gnu.org/licenses/>.
#
# The interactive user interfaces in modified source and object code
# versions of HexaPDF must display Appropriate Legal Notices, as required
# under Section 5 of the GNU Affero General Public License version 3.
#
# In accordance with Section 7(b) of the GNU Affero General Public
# License, a covered work must retain the producer line in every PDF that
# is created or manipulated using HexaPDF.
#
# If the GNU Affero General Public License doesn't fit your need,
# commercial licenses are available at <https://gettalong.at/hexapdf/>.
#++

require 'hexapdf/error'
require 'hexapdf/content/graphics_state'
require 'hexapdf/content/transformation_matrix'

module HexaPDF
  module Content

    # This module contains the content operator implementations.
    #
    # == General Information
    #
    # A PDF content streams consists of a series of instructions, operands followed by an operator
    # name. Each operator has a specific function, for example, the 'G' operator sets the stroke
    # color to the specified gray value.
    #
    # Since HexaPDF doesn't have a content stream rendering facility, it is only interested in the
    # effects an operator has on the graphics state. By calling the #invoke method with a
    # Content::Processor as first argument and the operands as the rest of the arguments, the
    # operator can modify the graphics state as needed. This ensures internal consistency and
    # correct operation.
    #
    # Operator objects are designed to be state-less. This means that the operands have to be
    # passed as arguments to the methods that need them.
    #
    #
    # == Operator Implementations
    #
    # HexaPDF comes with operator implementations for all PDF operations. These operator
    # implementations are derived from the Operator::BaseOperator class which provides all needed
    # methods.
    #
    # In general, an operator implementation is an object that responds to the following methods:
    #
    # #invoke(processor, *operands)::
    #   When an operator is invoked, it performs its job, e.g. changing the graphics state.
    #
    # #serialize(serializer, *operands)::
    #   Returns the operator together with its operands in serialized form.
    #
    # #name::
    #   Returns the name of the operator as String.
    #
    # See: PDF1.7 s8, s9
    module Operator

      # A base class for operator implementations.
      #
      # A default implementation for the #serialize method is provided. However, for performance
      # reasons each operator should provide a custom #serialize method.
      class BaseOperator

        # The name of the operator.
        attr_reader :name

        # Initialize the operator called +name+.
        def initialize(name)
          @name = name.freeze
        end

        # Invokes the operator so that it performs its job.
        #
        # This base version does nothing!
        def invoke(*)
        end

        # Returns the string representation of the operator, i.e.
        #
        #   operand1 operand2 operand3 name
        def serialize(serializer, *operands)
          result = ''.b
          operands.each do |operand|
            result << serializer.serialize(operand) << " "
          end
          result << name << "\n"
        end

      end

      # A specialized operator class for operators that take no arguments. Provides an optimized
      # #serialize method.
      class NoArgumentOperator < BaseOperator

        def initialize(name) #:nodoc:
          super(name)
          @serialized = "#{name}\n"
        end

        def invoke(_processor) # :nodoc:
        end

        # An optimized version of the serialization algorithm.
        #
        # See: BaseOperator#serialize
        def serialize(_serializer)
          @serialized
        end

      end

      # A specialized operator class for operators that take a single numeric argument. Provides
      # an optimized #serialize method.
      class SingleNumericArgumentOperator < BaseOperator

        # An optimized version of the serialization algorithm.
        #
        # See: BaseOperator#serialize
        def serialize(serializer, arg)
          "#{serializer.serialize_numeric(arg)} #{name}\n"
        end

      end

      # Implementation of the 'q' operator.
      #
      # See: PDF1.7 s8.4.4
      class SaveGraphicsState < NoArgumentOperator

        # Creates the operator.
        def initialize
          super('q')
        end

        def invoke(processor) #:nodoc:
          processor.graphics_state.save
        end

      end

      # Implementation of the 'Q' operator.
      #
      # See: PDF1.7 s8.4.4
      class RestoreGraphicsState < NoArgumentOperator

        # Creates the operator.
        def initialize
          super('Q')
        end

        def invoke(processor) #:nodoc:
          processor.graphics_state.restore
        end

      end

      # Implementation of the 'cm' operator.
      #
      # See: PDF1.7 s8.4.4
      class ConcatenateMatrix < BaseOperator

        # Creates the operator.
        def initialize
          super('cm')
        end

        def invoke(processor, a, b, c, d, e, f) #:nodoc:
          processor.graphics_state.ctm.premultiply(a, b, c, d, e, f)
        end

        def serialize(serializer, a, b, c, d, e, f) #:nodoc:
          "#{serializer.serialize_numeric(a)} #{serializer.serialize_numeric(b)} " \
            "#{serializer.serialize_numeric(c)} #{serializer.serialize_numeric(d)} " \
            "#{serializer.serialize_numeric(e)} #{serializer.serialize_numeric(f)} cm\n"
        end

      end

      # Implementation of the 'w' operator.
      #
      # See: PDF1.7 s8.4.4
      class SetLineWidth < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('w')
        end

        def invoke(processor, width) #:nodoc:
          processor.graphics_state.line_width = width
        end

      end

      # Implementation of the 'J' operator.
      #
      # See: PDF1.7 s8.4.4
      class SetLineCapStyle < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('J')
        end

        def invoke(processor, cap_style) #:nodoc:
          processor.graphics_state.line_cap_style = LineCapStyle.normalize(cap_style)
        end

      end

      # Implementation of the 'j' operator.
      #
      # See: PDF1.7 s8.4.4
      class SetLineJoinStyle < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('j')
        end

        def invoke(processor, join_style) #:nodoc:
          processor.graphics_state.line_join_style = LineJoinStyle.normalize(join_style)
        end

      end

      # Implementation of the 'M' operator.
      #
      # See: PDF1.7 s8.4.4
      class SetMiterLimit < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('M')
        end

        def invoke(processor, miter_limit) #:nodoc:
          processor.graphics_state.miter_limit = miter_limit
        end

      end

      # Implementation of the 'd' operator.
      #
      # See: PDF1.7 s8.4.4
      class SetLineDashPattern < BaseOperator

        # Creates the operator.
        def initialize
          super('d')
        end

        def invoke(processor, dash_array, dash_phase) #:nodoc:
          processor.graphics_state.line_dash_pattern = LineDashPattern.new(dash_array, dash_phase)
        end

        def serialize(serializer, dash_array, dash_phase) #:nodoc:
          "#{serializer.serialize_array(dash_array)} " \
            "#{serializer.serialize_integer(dash_phase)} d\n"
        end

      end

      # Implementation of the 'ri' operator.
      #
      # See: PDF1.7 s8.4.4
      class SetRenderingIntent < BaseOperator

        # Creates the operator.
        def initialize
          super('ri')
        end

        def invoke(processor, intent) #:nodoc:
          processor.graphics_state.rendering_intent = intent
        end

        def serialize(serializer, intent) #:nodoc:
          "#{serializer.serialize_symbol(intent)} ri\n"
        end

      end

      # Implementation of the 'gs' operator.
      #
      # Note: Only parameters supported by the GraphicsState/TextState classes are assigned, the
      # rest are ignored!
      #
      # See: PDF1.7 s8.4.4
      class SetGraphicsStateParameters < BaseOperator

        # Creates the operator.
        def initialize
          super('gs')
        end

        def invoke(processor, name) #:nodoc:
          dict = processor.resources.ext_gstate(name)

          ops = processor.operators
          ops[:w].invoke(processor, dict[:LW]) if dict.key?(:LW)
          ops[:J].invoke(processor, dict[:LC]) if dict.key?(:LC)
          ops[:j].invoke(processor, dict[:LJ]) if dict.key?(:LJ)
          ops[:M].invoke(processor, dict[:ML]) if dict.key?(:ML)
          ops[:d].invoke(processor, *dict[:D]) if dict.key?(:D)
          ops[:ri].invoke(processor, dict[:RI]) if dict.key?(:RI)
          # TODO: dict[:SMask] works differently than operator!

          # No content operator exists for the following parameters
          gs = processor.graphics_state
          gs.stroke_adjustment = dict[:SA] if dict.key?(:SA)
          gs.blend_mode = dict[:BM] if dict.key?(:BM)
          gs.stroke_alpha = dict[:CA] if dict.key?(:CA)
          gs.fill_alpha = dict[:ca] if dict.key?(:ca)
          gs.alpha_source = dict[:AIS] if dict.key?(:AIS)
          gs.text_knockout = dict[:TK] if dict.key?(:TK)
          if dict.key?(:Font)
            gs.font = processor.resources.document.deref(dict[:Font][0])
            gs.font_size = processor.resources.document.deref(dict[:Font][1])
          end
        end

        def serialize(serializer, name) #:nodoc:
          "#{serializer.serialize_symbol(name)} gs\n"
        end

      end

      # Implementation of the 'CS' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetStrokingColorSpace < BaseOperator

        # Creates the operator.
        def initialize
          super('CS')
        end

        def invoke(processor, name) #:nodoc:
          processor.graphics_state.stroke_color_space = processor.resources.color_space(name)
        end

        def serialize(serializer, name) #:nodoc:
          "#{serializer.serialize_symbol(name)} CS\n"
        end

      end

      # Implementation of the 'cs' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetNonStrokingColorSpace < BaseOperator

        # Creates the operator.
        def initialize
          super('cs')
        end

        def invoke(processor, name) #:nodoc:
          processor.graphics_state.fill_color_space = processor.resources.color_space(name)
        end

        def serialize(serializer, name) #:nodoc:
          "#{serializer.serialize_symbol(name)} cs\n"
        end

      end

      # Implementation of the 'SC' and 'SCN' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetStrokingColor < BaseOperator

        def invoke(processor, *operands) #:nodoc:
          processor.graphics_state.stroke_color =
            processor.graphics_state.stroke_color.color_space.prenormalized_color(*operands)
        end

      end

      # Implementation of the 'sc' and 'scn' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetNonStrokingColor < BaseOperator

        def invoke(processor, *operands) #:nodoc:
          processor.graphics_state.fill_color =
            processor.graphics_state.fill_color.color_space.prenormalized_color(*operands)
        end

      end

      # Implementation of the 'G' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetDeviceGrayStrokingColor < SingleNumericArgumentOperator

        def initialize #:nodoc:
          super('G')
        end

        def invoke(processor, gray) #:nodoc:
          processor.graphics_state.stroke_color =
            processor.resources.color_space(:DeviceGray).prenormalized_color(gray)
        end

      end

      # Implementation of the 'g' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetDeviceGrayNonStrokingColor < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('g')
        end

        def invoke(processor, gray) #:nodoc:
          processor.graphics_state.fill_color =
            processor.resources.color_space(:DeviceGray).prenormalized_color(gray)
        end

      end

      # Implementation of the 'RG' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetDeviceRGBStrokingColor < BaseOperator

        # Creates the operator.
        def initialize
          super('RG')
        end

        def invoke(processor, r, g, b) #:nodoc:
          processor.graphics_state.stroke_color =
            processor.resources.color_space(:DeviceRGB).prenormalized_color(r, g, b)
        end

        def serialize(serializer, r, g, b) #:nodoc:
          "#{serializer.serialize_numeric(r)} #{serializer.serialize_numeric(g)} " \
            "#{serializer.serialize_numeric(b)} RG\n"
        end

      end

      # Implementation of the 'rg' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetDeviceRGBNonStrokingColor < BaseOperator

        # Creates the operator.
        def initialize
          super('rg')
        end

        def invoke(processor, r, g, b) #:nodoc:
          processor.graphics_state.fill_color =
            processor.resources.color_space(:DeviceRGB).prenormalized_color(r, g, b)
        end

        def serialize(serializer, r, g, b) #:nodoc:
          "#{serializer.serialize_numeric(r)} #{serializer.serialize_numeric(g)} " \
            "#{serializer.serialize_numeric(b)} rg\n"
        end

      end

      # Implementation of the 'K' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetDeviceCMYKStrokingColor < BaseOperator

        # Creates the operator.
        def initialize
          super('K')
        end

        def invoke(processor, c, m, y, k) #:nodoc:
          processor.graphics_state.stroke_color =
            processor.resources.color_space(:DeviceCMYK).prenormalized_color(c, m, y, k)
        end

        def serialize(serializer, c, m, y, k) #:nodoc:
          "#{serializer.serialize_numeric(c)} #{serializer.serialize_numeric(m)} " \
            "#{serializer.serialize_numeric(y)} #{serializer.serialize_numeric(k)} K\n"
        end

      end

      # Implementation of the 'k' operator.
      #
      # See: PDF1.7 s8.6.8
      class SetDeviceCMYKNonStrokingColor < BaseOperator

        # Creates the operator.
        def initialize
          super('k')
        end

        def invoke(processor, c, m, y, k) #:nodoc:
          processor.graphics_state.fill_color =
            processor.resources.color_space(:DeviceCMYK).prenormalized_color(c, m, y, k)
        end

        def serialize(serializer, c, m, y, k) #:nodoc:
          "#{serializer.serialize_numeric(c)} #{serializer.serialize_numeric(m)} " \
            "#{serializer.serialize_numeric(y)} #{serializer.serialize_numeric(k)} k\n"
        end

      end

      # Implementation of the 'm' operator.
      #
      # See: PDF1.7 s8.5.2.1
      class MoveTo < BaseOperator

        # Creates the operator.
        def initialize
          super('m')
        end

        def invoke(processor, _x, _y) #:nodoc:
          processor.graphics_object = :path
        end

        def serialize(serializer, x, y) #:nodoc:
          "#{serializer.serialize_numeric(x)} #{serializer.serialize_numeric(y)} m\n"
        end

      end

      # Implementation of the 're' operator.
      #
      # See: PDF1.7 s8.5.2.1
      class AppendRectangle < BaseOperator

        # Creates the operator.
        def initialize
          super('re')
        end

        def invoke(processor, _x, _y, _w, _h) #:nodoc:
          processor.graphics_object = :path
        end

        def serialize(serializer, x, y, w, h) #:nodoc:
          "#{serializer.serialize_numeric(x)} #{serializer.serialize_numeric(y)} " \
            "#{serializer.serialize_numeric(w)} #{serializer.serialize_numeric(h)} re\n"
        end

      end

      # Implementation of the 'l' operator.
      #
      # See: PDF1.7 s8.5.2.1
      class LineTo < BaseOperator

        # Creates the operator.
        def initialize
          super('l')
        end

        def invoke(_processor, _x, _y) #:nodoc:
        end

        def serialize(serializer, x, y) #:nodoc:
          "#{serializer.serialize_numeric(x)} #{serializer.serialize_numeric(y)} l\n"
        end

      end

      # Implementation of the 'c' operators.
      #
      # See: PDF1.7 s8.5.2.1
      class CurveTo < BaseOperator

        # Creates the operator.
        def initialize
          super('c')
        end

        def serialize(serializer, x1, y1, x2, y2, x3, y3) #:nodoc:
          "#{serializer.serialize_numeric(x1)} #{serializer.serialize_numeric(y1)} " \
            "#{serializer.serialize_numeric(x2)} #{serializer.serialize_numeric(y2)} " \
            "#{serializer.serialize_numeric(x3)} #{serializer.serialize_numeric(y3)} c\n"
        end

      end

      # Implementation of the 'v' operators.
      #
      # See: PDF1.7 s8.5.2.1
      class CurveToNoFirstControlPoint < BaseOperator

        # Creates the operator.
        def initialize
          super('v')
        end

        def serialize(serializer, x2, y2, x3, y3) #:nodoc:
          "#{serializer.serialize_numeric(x2)} #{serializer.serialize_numeric(y2)} " \
            "#{serializer.serialize_numeric(x3)} #{serializer.serialize_numeric(y3)} v\n"
        end

      end

      # Implementation of the 'y' operators.
      #
      # See: PDF1.7 s8.5.2.1
      class CurveToNoSecondControlPoint < BaseOperator

        # Creates the operator.
        def initialize
          super('y')
        end

        def serialize(serializer, x1, y1, x3, y3) #:nodoc:
          "#{serializer.serialize_numeric(x1)} #{serializer.serialize_numeric(y1)} " \
            "#{serializer.serialize_numeric(x3)} #{serializer.serialize_numeric(y3)} y\n"
        end

      end

      # Implementation of the 'S', 's', 'f', 'F', 'f*', 'B', 'B*', 'b', 'b*' and 'n' operators.
      #
      # See: PDF1.7 s8.5.3.1
      class EndPath < NoArgumentOperator

        def invoke(processor) #:nodoc:
          processor.graphics_object = :none
        end

      end

      # Implementation of the 'W' and 'W*' operators.
      #
      # See: PDF1.7 s8.5.4
      class ClipPath < NoArgumentOperator

        def invoke(processor) #:nodoc:
          processor.graphics_object = :clipping_path
        end

      end

      # Implementation of the 'BI' operator which handles the *complete* inline image, i.e. the
      # 'ID' and 'EI' operators are never encountered.
      #
      # See: PDF1.7 s8.9.7
      class InlineImage < BaseOperator

        # Creates the operator.
        def initialize
          super('BI')
        end

        def serialize(serializer, dict, data) #:nodoc:
          result = +"BI\n"
          dict.each do |k, v|
            result << serializer.serialize_symbol(k) << ' '
            result << serializer.serialize(v) << ' '
          end
          result << "ID\n" << data << "EI\n"
        end

      end

      # Implementation of the 'Tc' operator.
      #
      # See: PDF1.7 s9.3.1
      class SetCharacterSpacing < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('Tc')
        end

        def invoke(processor, char_space) #:nodoc:
          processor.graphics_state.character_spacing = char_space
        end

      end

      # Implementation of the 'Tw' operator.
      #
      # See: PDF1.7 s9.3.1
      class SetWordSpacing < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('Tw')
        end

        def invoke(processor, word_space) #:nodoc:
          processor.graphics_state.word_spacing = word_space
        end

      end

      # Implementation of the 'Tz' operator.
      #
      # See: PDF1.7 s9.3.1
      class SetHorizontalScaling < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('Tz')
        end

        def invoke(processor, scale) #:nodoc:
          processor.graphics_state.horizontal_scaling = scale
        end

      end

      # Implementation of the 'TL' operator.
      #
      # See: PDF1.7 s9.3.1
      class SetLeading < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('TL')
        end

        def invoke(processor, leading) #:nodoc:
          processor.graphics_state.leading = leading
        end

      end

      # Implementation of the 'Tf' operator.
      #
      # See: PDF1.7 s9.3.1
      class SetFontAndSize < BaseOperator

        # Creates the operator.
        def initialize
          super('Tf')
        end

        def invoke(processor, font, size) #:nodoc:
          processor.graphics_state.font = processor.resources.font(font)
          processor.graphics_state.font_size = size
        end

        def serialize(serializer, font, size) #:nodoc:
          "#{serializer.serialize_symbol(font)} #{serializer.serialize_numeric(size)} Tf\n"
        end

      end

      # Implementation of the 'Tr' operator.
      #
      # See: PDF1.7 s9.3.1
      class SetTextRenderingMode < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('Tr')
        end

        def invoke(processor, rendering_mode) #:nodoc:
          processor.graphics_state.text_rendering_mode = TextRenderingMode.normalize(rendering_mode)
        end

      end

      # Implementation of the 'Ts' operator.
      #
      # See: PDF1.7 s9.3.1
      class SetTextRise < SingleNumericArgumentOperator

        # Creates the operator.
        def initialize
          super('Ts')
        end

        def invoke(processor, rise) #:nodoc:
          processor.graphics_state.text_rise = rise
        end

      end

      # Implementation of the 'BT' operator.
      #
      # See: PDF1.7 s9.4.1
      class BeginText < NoArgumentOperator

        def initialize #:nodoc:
          super('BT')
        end

        def invoke(processor) #:nodoc:
          processor.graphics_object = :text
          processor.graphics_state.tm = TransformationMatrix.new
          processor.graphics_state.tlm = TransformationMatrix.new
        end

      end

      # Implementation of the 'ET' operator.
      #
      # See: PDF1.7 s9.4.1
      class EndText < NoArgumentOperator

        # Creates the operator.
        def initialize
          super('ET')
        end

        def invoke(processor) #:nodoc:
          processor.graphics_object = :none
          processor.graphics_state.tm = nil
          processor.graphics_state.tlm = nil
        end

      end

      # Implementation of the 'Td' operator.
      #
      # See: PDF1.7 s9.4.2
      class MoveText < BaseOperator

        # Creates the operator.
        def initialize
          super('Td')
        end

        def invoke(processor, tx, ty) #:nodoc:
          processor.graphics_state.tlm.translate(tx, ty)
          processor.graphics_state.tm = processor.graphics_state.tlm.dup
        end

        def serialize(serializer, tx, ty) #:nodoc:
          "#{serializer.serialize_numeric(tx)} #{serializer.serialize_numeric(ty)} Td\n"
        end

      end

      # Implementation of the 'TD' operator.
      #
      # See: PDF1.7 s9.4.2
      class MoveTextAndSetLeading < BaseOperator

        # Creates the operator.
        def initialize
          super('TD')
        end

        def invoke(processor, tx, ty) #:nodoc:
          processor.operators[:TL].invoke(processor, -ty)
          processor.operators[:Td].invoke(processor, tx, ty)
        end

        def serialize(serializer, tx, ty) #:nodoc:
          "#{serializer.serialize_numeric(tx)} #{serializer.serialize_numeric(ty)} TD\n"
        end

      end

      # Implementation of the 'Tm' operator.
      #
      # See: PDF1.7 s9.4.2
      class SetTextMatrix < BaseOperator

        # Creates the operator.
        def initialize
          super('Tm')
        end

        def invoke(processor, a, b, c, d, e, f) #:nodoc:
          processor.graphics_state.tm = TransformationMatrix.new(a, b, c, d, e, f)
          processor.graphics_state.tlm = processor.graphics_state.tm.dup
        end

        def serialize(serializer, a, b, c, d, e, f) #:nodoc:
          "#{serializer.serialize_numeric(a)} #{serializer.serialize_numeric(b)} " \
            "#{serializer.serialize_numeric(c)} #{serializer.serialize_numeric(d)} " \
            "#{serializer.serialize_numeric(e)} #{serializer.serialize_numeric(f)} Tm\n"
        end

      end

      # Implementation of the 'T*' operator.
      #
      # See: PDF1.7 s9.4.2
      class MoveTextNextLine < NoArgumentOperator

        # Creates the operator.
        def initialize
          super('T*')
        end

        def invoke(processor) #:nodoc:
          leading = processor.graphics_state.leading
          processor.operators[:Td].invoke(processor, 0, -leading)
        end

      end

      # Implementation of the 'Tj' operator.
      #
      # See: PDF1.7 s9.4.3
      class ShowText < BaseOperator

        # Creates the operator.
        def initialize
          super('Tj')
        end

        def serialize(serializer, text) #:nodoc:
          "#{serializer.serialize_string(text)}Tj\n"
        end

      end

      # Implementation of the ' operator.
      #
      # See: PDF1.7 s9.4.3
      class MoveTextNextLineAndShowText < BaseOperator

        def initialize #:nodoc:
          super("'")
        end

        def invoke(processor, text) #:nodoc:
          processor.operators[:'T*'].invoke(processor)
          processor.operators[:Tj].invoke(processor, text)
        end

        def serialize(serializer, text)
          "#{serializer.serialize_string(text)}'\n"
        end

      end

      # Implementation of the " operator.
      #
      # See: PDF1.7 s9.4.3
      class SetSpacingMoveTextNextLineAndShowText < BaseOperator

        # Creates the operator.
        def initialize
          super('"')
        end

        def invoke(processor, word_space, char_space, text) #:nodoc:
          processor.operators[:Tw].invoke(processor, word_space)
          processor.operators[:Tc].invoke(processor, char_space)
          processor.operators[:"'"].invoke(processor, text)
        end

        def serialize(serializer, word_space, char_space, text) #:nodoc:
          "#{serializer.serialize_numeric(word_space)} " \
            "#{serializer.serialize_numeric(char_space)} " \
            "#{serializer.serialize_string(text)}\"\n"
        end

      end

      # Implementation of the 'TJ' operator.
      #
      # See: PDF1.7 s9.4.3
      class ShowTextWithPositioning < BaseOperator

        # Creates the operator.
        def initialize
          super('TJ')
        end

        def serialize(serializer, array) #:nodoc:
          "#{serializer.serialize_array(array)}TJ\n"
        end

      end

      # Mapping of operator names to their default operator implementations.
      DEFAULT_OPERATORS = {
        q: SaveGraphicsState.new,
        Q: RestoreGraphicsState.new,
        cm: ConcatenateMatrix.new,
        w: SetLineWidth.new,
        J: SetLineCapStyle.new,
        j: SetLineJoinStyle.new,
        M: SetMiterLimit.new,
        d: SetLineDashPattern.new,
        ri: SetRenderingIntent.new,
        gs: SetGraphicsStateParameters.new,
        CS: SetStrokingColorSpace.new,
        cs: SetNonStrokingColorSpace.new,
        SC: SetStrokingColor.new('SC'),
        SCN: SetStrokingColor.new('SCN'),
        sc: SetNonStrokingColor.new('sc'),
        scn: SetNonStrokingColor.new('scn'),
        G: SetDeviceGrayStrokingColor.new,
        g: SetDeviceGrayNonStrokingColor.new,
        RG: SetDeviceRGBStrokingColor.new,
        rg: SetDeviceRGBNonStrokingColor.new,
        K: SetDeviceCMYKStrokingColor.new,
        k: SetDeviceCMYKNonStrokingColor.new,
        m: MoveTo.new,
        re: AppendRectangle.new,
        l: LineTo.new,
        c: CurveTo.new,
        v: CurveToNoFirstControlPoint.new,
        y: CurveToNoSecondControlPoint.new,
        h: NoArgumentOperator.new('h'),
        S: EndPath.new('S'),
        s: EndPath.new('s'),
        f: EndPath.new('f'),
        F: EndPath.new('F'),
        'f*'.to_sym => EndPath.new('f*'),
        B: EndPath.new('B'),
        'B*'.to_sym => EndPath.new('B*'),
        b: EndPath.new('b'),
        'b*'.to_sym => EndPath.new('b*'),
        n: EndPath.new('n'),
        W: ClipPath.new('W'),
        'W*'.to_sym => ClipPath.new('W*'),

        BI: InlineImage.new,

        BT: BeginText.new,
        ET: EndText.new,
        Tc: SetCharacterSpacing.new,
        Tw: SetWordSpacing.new,
        Tz: SetHorizontalScaling.new,
        TL: SetLeading.new,
        Tf: SetFontAndSize.new,
        Tr: SetTextRenderingMode.new,
        Ts: SetTextRise.new,
        Td: MoveText.new,
        TD: MoveTextAndSetLeading.new,
        Tm: SetTextMatrix.new,
        'T*'.to_sym => MoveTextNextLine.new,
        Tj: ShowText.new,
        '\''.to_sym => MoveTextNextLineAndShowText.new,
        '"'.to_sym => SetSpacingMoveTextNextLineAndShowText.new,
        TJ: ShowTextWithPositioning.new,
      }
      DEFAULT_OPERATORS.default_proc = proc {|h, k| h[k] = BaseOperator.new(k.to_s) }

    end

  end
end