Class: Prawn::FontMetricCache

Inherits:
Object
  • Object
show all
Defined in:
lib/prawn/font_metric_cache.rb

Overview

Cache used internally by Document instances to calculate the width of various strings for layout purposes.

Defined Under Namespace

Classes: CacheEntry

Instance Method Summary collapse

Constructor Details

#initialize(document) ⇒ FontMetricCache

Returns a new instance of FontMetricCache.



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# File 'lib/prawn/font_metric_cache.rb', line 11

def initialize(document)
  @document = document

  @cache = {}
end

Instance Method Details

#width_of(string, options) ⇒ Number

Get width of string.

Parameters:

  • string (String)
  • options (Hash{Symbol => any})

Options Hash (options):

  • :style (Symbol)
  • :size (Number)
  • :kerning (Boolean) — default: false

Returns:

  • (Number) 


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# File 'lib/prawn/font_metric_cache.rb', line 25

def width_of(string, options)
  f =
    if options[:style]
      # override style with :style => :bold
      @document.find_font(@document.font.family, style: options[:style])
    else
      @document.font
    end

  encoded_string = f.normalize_encoding(string)

  key = CacheEntry.new(f, @document.font_size, options, encoded_string)

  @cache[key] ||= f.compute_width_of(encoded_string, options)

  length = @cache[key]

  character_count = @document.font.character_count(encoded_string)
  if character_count.positive?
    length += @document.character_spacing * (character_count - 1)
  end

  length
end