class Prawn::FontMetricCache

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

@private

Constants

CacheEntry

Public Class Methods

new(document) click to toggle source
# File lib/prawn/font_metric_cache.rb, line 18
def initialize(document)
  @document = document

  @cache = {}
end

Public Instance Methods

width_of(string, options) click to toggle source
# File lib/prawn/font_metric_cache.rb, line 24
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, 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