Class: HexaPDF::Layout::Style::Layers

Inherits:
Object
  • Object
show all
Defined in:
lib/hexapdf/layout/style.rb

Overview

Represents layers that can be drawn under or over a box.

There are two ways to specify layers via #add:

  • Directly by providing a callable object.

  • By reference to a callable object or class in the ‘style.layers_map’ configuration option. The reference name is looked up in the configuration option using HexaPDF::Configuration#constantize. If the resulting object is a callable object, it is used; otherwise it is assumed that it is a class and an object is instantiated, passing in any options given on #add.

The object resolved in this way needs to respond to #call(canvas, box) where canvas is the HexaPDF::Content::Canvas object on which it should be drawn and box is a box-like object (e.g. Box or TextFragment). The coordinate system is translated so that the origin is at the bottom left corner of the box during the drawing operations.

Instance Method Summary collapse

Constructor Details

#initialize(layers = []) ⇒ Layers

Creates a new Layers object popuplated with the given layers.



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# File 'lib/hexapdf/layout/style.rb', line 371

def initialize(layers = [])
  @layers = layers
end

Instance Method Details

#add(name = nil, **options, &block) ⇒ Object

:call-seq:

layers.add {|canvas, box| block}
layers.add(name, **options)

Adds a new layer object.

The layer object can either be specified as a block or by reference to a configured layer object in ‘style.layers_map’. In this case name is used as the reference and the options are passed to layer object if it needs initialization.



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# File 'lib/hexapdf/layout/style.rb', line 384

def add(name = nil, **options, &block)
  if block_given?
    @layers << block
  elsif name
    @layers << [name, options]
  else
    raise ArgumentError, "Layer object name or block missing"
  end
end

#draw(canvas, x, y, box) ⇒ Object

Draws all layer objects onto the canvas at the position [x, y] for the given box.



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# File 'lib/hexapdf/layout/style.rb', line 395

def draw(canvas, x, y, box)
  return if none?

  canvas.translate(x, y) do
    each(canvas.context.document.config) do |layer|
      canvas.save_graphics_state { layer.call(canvas, box) }
    end
  end
end

#each(config) ⇒ Object

Yields all layer objects. Objects that have been specified via a reference are first resolved using the provided configuration object.



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# File 'lib/hexapdf/layout/style.rb', line 407

def each(config) #:yield: layer
  @layers.each do |obj, options|
    obj = config.constantize('style.layers_map', obj) unless obj.respond_to?(:call)
    obj = obj.new(**options) unless obj.respond_to?(:call)
    yield(obj)
  end
end

#none? ⇒ Boolean

Returns true if there are no layers defined.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/layout/style.rb', line 416

def none?
  @layers.empty?
end