Class: HexaPDF::Layout::Line

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

Overview

A Line describes a line of text and can contain TextFragment objects or InlineBox objects.

The items of a line fragment are aligned along the x-axis which coincides with the text baseline. The vertical alignment is determined by the value of the #valign method:

:text_top

Align the top of the box with the top of the text of the Line.

:text_bottom

Align the bottom of the box with the bottom of the text of the Line.

:baseline

Align the bottom of the box with the baseline of the Line.

:top

Align the top of the box with the top of the Line.

:bottom

Align the bottom of the box with the bottom of the Line.

:text

This is a special alignment value for text fragment objects. The text fragment is aligned on the baseline and its minimum and maximum y-coordinates are used when calculating the line’s #text_y_min and #text_y_max.

This value may be used by other objects if they should be handled similar to text fragments, e.g. graphical representation of characters (think: emoji fonts).

Item Requirements

Each item of a line fragment has to respond to the following methods:

#x_min

The minimum x-coordinate of the item.

#x_max

The maximum x-coordinate of the item.

#width

The width of the item.

#valign

The vertical alignment of the item (see above).

#draw(canvas, x, y)

Should draw the item onto the canvas at the position (x, y).

If an item has a vertical alignment of :text, it additionally has to respond to the following methods:

#y_min

The minimum y-coordinate of the item.

#y_max

The maximum y-coordinate of the item.

Otherwise (i.e. a vertical alignment different from :text), the following method must be implemented:

#height

The height of the item.

Defined Under Namespace

Classes: HeightCalculator

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(items = []) ⇒ Line

Creates a new Line object, adding all given items to it.



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# File 'lib/hexapdf/layout/line.rb', line 186

def initialize(items = [])
  @items = []
  items.each {|i| add(i) }
  @x_offset = 0
  @y_offset = 0
end

Instance Attribute Details

#items ⇒ Object

The items: TextFragment and InlineBox objects



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# File 'lib/hexapdf/layout/line.rb', line 173

def items
  @items
end

#x_offset ⇒ Object

An optional horizontal offset that should be taken into account when positioning the line.



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# File 'lib/hexapdf/layout/line.rb', line 176

def x_offset
  @x_offset
end

#y_offset ⇒ Object

An optional vertical offset that should be taken into account when positioning the line.

For the first line in a paragraph this describes the offset from the top of the box to the baseline of the line. For all other lines it describes the offset from the previous baseline to the baseline of this line.



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# File 'lib/hexapdf/layout/line.rb', line 183

def y_offset
  @y_offset
end

Instance Method Details

#add(item) ⇒ Object Also known as: <<

Adds the given item at the end of the item list.

If both the item and the last item in the item list are TextFragment objects with the same attributes, they are combined.

Note: The cache is not cleared!



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# File 'lib/hexapdf/layout/line.rb', line 199

def add(item)
  last = @items.last
  if last.instance_of?(item.class) && item.kind_of?(TextFragment) &&
      last.attributes_hash == item.attributes_hash
    if last.items.frozen?
      @items[-1] = last = last.dup
      last.items = last.items.dup
    end
    last.items[last.items.length, 0] = item.items
    last.clear_cache
  else
    @items << item
  end
  self
end

#clear_cache ⇒ Object

:call-seq:

line.clear_cache   -> line

Clears all cached values.

This method needs to be called if the line’s items are changed!



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# File 'lib/hexapdf/layout/line.rb', line 298

def clear_cache
  @x_max = @y_min = @y_max = @text_y_min = @text_y_max = @width = nil
  self
end

#each ⇒ Object

:call-seq:

line.each {|item, x, y| block }

Yields each item together with its horizontal offset from 0 and vertical offset from the baseline.



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# File 'lib/hexapdf/layout/line.rb', line 221

def each
  x = 0
  @items.each do |item|
    y = case item.valign
        when :text, :baseline then 0
        when :top then y_max - item.height
        when :text_top then text_y_max - item.height
        when :text_bottom then text_y_min
        when :bottom then y_min
        else
          raise HexaPDF::Error, "Unknown inline box alignment #{item.valign}"
        end
    yield(item, x, y)
    x += item.width
  end
end

#height ⇒ Object

The height of the line fragment.



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# File 'lib/hexapdf/layout/line.rb', line 278

def height
  y_max - y_min
end

#ignore_justification! ⇒ Object

Specifies that this line should not be justified if line justification is used.



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# File 'lib/hexapdf/layout/line.rb', line 283

def ignore_justification!
  @ignore_justification = true
end

#ignore_justification? ⇒ Boolean

Returns true if justification should be ignored for this line.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/layout/line.rb', line 288

def ignore_justification?
  defined?(@ignore_justification) && @ignore_justification
end

#text_y_max ⇒ Object

The maximum y-coordinate of any TextFragment item of the line.



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# File 'lib/hexapdf/layout/line.rb', line 268

def text_y_max
  @text_y_max ||= calculate_y_dimensions[3]
end

#text_y_min ⇒ Object

The minimum y-coordinate of any TextFragment item of the line.



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# File 'lib/hexapdf/layout/line.rb', line 256

def text_y_min
  @text_y_min ||= calculate_y_dimensions[2]
end

#width ⇒ Object

The width of the line fragment.



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# File 'lib/hexapdf/layout/line.rb', line 273

def width
  @width ||= @items.sum(&:width)
end

#x_max ⇒ Object

The maximum x-coordinate of the whole line.



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# File 'lib/hexapdf/layout/line.rb', line 244

def x_max
  @x_max ||= width + (items[-1].x_max - items[-1].width)
end

#x_min ⇒ Object

The minimum x-coordinate of the whole line.



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# File 'lib/hexapdf/layout/line.rb', line 239

def x_min
  @items[0].x_min
end

#y_max ⇒ Object

The maximum y-coordinate of any item of the line.

It is always greater than or equal to zero.



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# File 'lib/hexapdf/layout/line.rb', line 263

def y_max
  @y_max ||= calculate_y_dimensions[1]
end

#y_min ⇒ Object

The minimum y-coordinate of any item of the line.

It is always lower than or equal to zero.



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# File 'lib/hexapdf/layout/line.rb', line 251

def y_min
  @y_min ||= calculate_y_dimensions[0]
end