rhythm.styl

// Work out what the base line-height is in pixels
$base-line-height = $base-font-size * $line-height-scale

rhythm($font-size-multiplier, $margin-top-multiplier = false, $margin-bottom-multiplier = false, $line-count = false)

	if $font-size-multiplier == "base"
		font-size: $base-font-size
		line-height: $base-line-height

	else
		if $true-scale
			$font-size-multiplier <= 1 ? $font-size-multiplier = 0 : $font-size-multiplier = $font-size-multiplier - 1

		$local-font-scale = $font-scale ** $font-size-multiplier
		$local-font-size = $base-font-size * $local-font-scale
		$local-line-count = $line-count ? $line-count : ceil(unit($local-font-size / $base-line-height, ''))
		$local-line-height = $local-line-count * $base-line-height

		// Values calculated in pixels
		$computed = {}

		// Values calculated in ems, or rems
		$converted = {}

		if $unit == "px" || $unit == "pxrem"
			$computed['font-size'] = $local-font-size
			$computed['line-height'] = $local-line-height
			if $margin-top-multiplier
				$computed['margin-top'] = $base-line-height * $margin-top-multiplier
			if $margin-bottom-multiplier
				$computed['margin-bottom'] = $base-line-height * $margin-bottom-multiplier

		if $unit == "em"
			$converted['font-size'] = $local-font-size / $base-font-size
			$converted['line-height'] = $local-line-height / $local-font-size
			if $margin-top-multiplier
				$converted['margin-top'] = ($base-line-height / $local-font-size) * $margin-top-multiplier
			if $margin-bottom-multiplier
				$converted['margin-bottom'] = ($base-line-height / $local-font-size) * $margin-bottom-multiplier

		if $unit == "rem" || $unit == "pxrem"
			$converted['font-size'] = $local-font-size / $base-font-size
			$converted['line-height'] = $local-line-height / $base-font-size
			if $margin-top-multiplier
				$converted['margin-top'] = ($base-line-height / $base-font-size) * $margin-top-multiplier
			if $margin-bottom-multiplier
				$converted['margin-bottom'] = ($base-line-height / $base-font-size) * $margin-bottom-multiplier

		// If unit is "pxrem" then set unit to "rem" for correct output
		$unit == "pxrem" ? $unit = "rem" : $unit = $unit

		// Output any computed values
		for $prop in $computed
			add-property($prop, $computed[$prop])

		// Output any converted values and append correct unit
		for $prop in $converted
			$converted[$prop] = unit($converted[$prop], $unit)
			add-property($prop, $converted[$prop])