Class: CSSensible::Finder

Inherits:
Object
  • Object
show all
Defined in:
lib/cssensible/finder.rb

Constant Summary collapse

MIN_LINE_HEIGHT_EM_VALUE =

A line-height should be at least this em-value to improve readability.

EmValue.new(1.3)
MIN_FONT_SIZE_PX =

Size in pixel a font should at least be to be readable

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Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(font_sizes, min_line_height_em = MIN_LINE_HEIGHT_EM_VALUE) ⇒ Finder

Returns a new Vertical Grid Finder based on the font size passed to new.



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# File 'lib/cssensible/finder.rb', line 16

def initialize(font_sizes, min_line_height_em = MIN_LINE_HEIGHT_EM_VALUE)
  @font_sizes = font_sizes.sort
  @min_line_height_em = min_line_height_em
end

Instance Attribute Details

#font_size ⇒ Object (readonly)

Returns the value of attribute font_size.



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# File 'lib/cssensible/finder.rb', line 13

def font_size
  @font_size
end

Instance Method Details

#find ⇒ Object

Finds sensible vertical grids based on the parameters given in new.



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# File 'lib/cssensible/finder.rb', line 22

def find
  vertical_grids = []

  # for the first iteration, all line-heights from the smallest font-size
  # to two times the largest font-size are potentially possible
  line_heights = (@font_sizes.first .. @font_sizes.last * 2).to_a

  # go through required font-sizes and identify all line-heights that work
  # with all of them
  @font_sizes.each do |font_size|
    possible_line_heights = []

    # keep line-height if it can be expressed in valid 'em' for this
    # font-size
    line_heights.each do |line_height|
      if EmValue.new(line_height / font_size.to_f).usable?
        possible_line_heights << line_height
      end
    end

    # for next iteration, only check line-heights that work with this
    # font-size
    line_heights = possible_line_heights
  end

  line_heights.each do |line_height|
    base_line_height = line_height
    font_sizes_to_line_height = {}

    # we will increment the line-height as soon as a resulting em-value
    # falls underneath @min_line_height_em; to prevent large differences, we
    # add half of our base line-height if possible
    if line_height.even?
      line_height_increment = line_height / 2
    else
      line_height_increment = line_height
    end

    # to offer a larger range of available font-sizes, we start from the
    # smallest possible font-size and end at don't just end at the biggest
    # supplied font-size
    (MIN_FONT_SIZE_PX .. @font_sizes.last * 2).each do |font_size|
      line_height_em = EmValue.new(line_height / font_size.to_f)

      # increment line-height if we fall below the minimum value
      if line_height_em < @min_line_height_em
        line_height += line_height_increment
        redo
      end

      # map font-size and line-height for this grid
      if line_height_em.usable? && line_height_em >= @min_line_height_em
        font_sizes_to_line_height[font_size] = line_height_em
      end
    end

    # add grid to results
    # TODO can font_sizes_to_line_height ever really be empty?
    unless font_sizes_to_line_height.empty?
      vertical_grid = VerticalGrid.new(@font_sizes, base_line_height,
          font_sizes_to_line_height)
      vertical_grids << vertical_grid
    end
  end

  vertical_grids
end