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# encoding: utf-8
#
# font_metric_cache.rb : The Prawn font class
#
# Copyright Dec 2012, Kenneth Kalmer. All Rights Reserved.
#
# This is free software. Please see the LICENSE and COPYING files for details.
#
module Prawn
# Cache used internally by Prawn::Document instances to calculate the width
# of various strings for layout purposes.
#
# @private
class FontMetricCache
CacheEntry = Struct.new( :font, :options, :string )
def initialize( document )
@document = document
@cache = {}
end
def width_of( string, options )
f = if options[:style]
# override style with :style => :bold
@document.find_font(@document.font ? @document.font.name : 'Helvetica',
:style => options[:style])
else
@document.font
end
key = CacheEntry.new( f, options, string )
unless length = @cache[ key ]
length = @cache[ key ] = f.compute_width_of(string, options)
end
length +
(@document.character_spacing * @document.font.character_count(string))
end
end
end
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