Add support for Sass functions.

lib/sass.rb

@@ -440,6 +440,21 @@ $LOAD_PATH << dir unless $LOAD_PATH.include?(dir)
 #     #main h6 {
 #       font: italic small-caps bold 1.1em sans-serif; }
 #
+# === Functions
+#
+# Functions can be performed on Sass constants using the familiar CSS function syntax.
+# For example:
+#
+#   #main
+#     :color = hsl(0, 100%, 50%)
+#
+# is compiled to:
+#
+#   #main {
+#     color: #ff0000; }
+#
+# Available functions are defined in Sass::Constant::Functions.
+#
 # == Directives
 #
 # Directives allow the author to directly issue instructions to the Sass compiler.

lib/sass/constant.rb

@@ -2,7 +2,10 @@ require 'sass/constant/operation'
 require 'sass/constant/literal'
 
 module Sass
-  module Constant # :nodoc:
+  # This module contains various constant-script related functionality.
+  module Constant
+    # :stopdoc:
+
     # The character that begins a constant.
     CONSTANT_CHAR   = ?!
 
@@ -254,5 +257,6 @@ module Sass
         to_return
       end
     end
+    # :startdoc:
   end
 end

lib/sass/constant/color.rb

@@ -1,6 +1,6 @@
 require 'sass/constant/literal'
 
-module Sass::Constant # :nodoc:
+module Sass::Constant
   class Color < Literal # :nodoc:
 
     HTML4_COLORS = {

lib/sass/constant/functions.rb

@@ -0,0 +1,55 @@
+module Sass::Constant
+  # Methods in this module are accessible from the Sass constant context.
+  # For example, you can write
+  #
+  #   color = hsl(120, 100%, 50%)
+  #
+  # and it will call Sass::Constant::Functions#hsl.
+  #
+  # You can add your own functions to this module,
+  # but there are a few things to keep in mind.
+  # First of all, the arguments passed are (currently undocumented) Sass::Constant::Literal objects,
+  # Literal objects are also the expected return values.
+  #
+  # Second, making Ruby functions accessible from Sass introduces the temptation
+  # to do things like database access within stylesheets.
+  # This temptation must be resisted.
+  # Keep in mind that Sass stylesheets are only compiled once
+  # at a somewhat indeterminate time
+  # and then left as static CSS files.
+  # Any dynamic CSS should be left in <style> tags in the HTML.
+  module Functions
+    instance_methods.each { |m| undef_method m unless m =~ /^__/ }
+    extend self
+
+    # Creates a Sass::Constant::Color object from hue, saturation, and lightness.
+    # As per the CSS3 spec (http://www.w3.org/TR/css3-color/#hsl-color),
+    # the units of hue are taken to be degrees,
+    # and the units of saturation and lightness are taken to be percentages.
+    # THis is not validated, though.
+    def hsl(h, s, l)
+      # This algorithm is from http://www.w3.org/TR/css3-color#hsl-color
+      h, s, l = [h, s, l].map { |a| a.value }
+      h = (h % 360) / 360.0
+      s /= 100.0
+      l /= 100.0
+
+      m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s
+      m1 = l * 2 - m2
+      Color.new([hue_to_rgb(m1, m2, h + 1.0/3),
+                 hue_to_rgb(m1, m2, h),
+                 hue_to_rgb(m1, m2, h - 1.0/3)].map { |c| (c * 0xff).round })
+    end
+
+    private
+
+    def hue_to_rgb(m1, m2, h)
+      h += 1 if h < 0
+      h -= 1 if h > 1
+      return m1 + (m2 - m1) * h * 6 if h * 6 < 1
+      return m2 if h * 2 < 1
+      return m1 + (m2 - m1) * (2.0/3 - h) * 6 if h * 3 < 2
+      return m1
+    end
+  end
+end

lib/sass/constant/literal.rb

@@ -1,5 +1,7 @@
+# :stopdoc:
 # Let the subclasses see the superclass
-module Sass::Constant; class Literal; end; end; # :nodoc:
+module Sass::Constant; class Literal; end; end;
+# :startdoc:
 
 require 'sass/constant/string'
 require 'sass/constant/number'
@@ -27,7 +29,11 @@ class Sass::Constant::Literal # :nodoc:
   end
 
   def initialize(value = nil)
-    self.parse(value) if value
+    if value.is_a?(String)
+      self.parse(value)
+    else
+      @value = value
+    end
   end
 
   def perform
@@ -46,6 +52,10 @@ class Sass::Constant::Literal # :nodoc:
     value.inspect
   end
 
+  def to_arglist
+    [self]
+  end
+
   attr_reader :value
 
   protected

lib/sass/constant/nil.rb

@@ -1,9 +1,13 @@
 require 'sass/constant/literal'
 
-module Sass::Constant # :nodoc:
+module Sass::Constant
   class Nil < Literal # :nodoc:
     def to_s
       ''
     end
+
+    def to_arglist
+      []
+    end
   end
 end

lib/sass/constant/number.rb

@@ -1,6 +1,6 @@
 require 'sass/constant/literal'
 
-module Sass::Constant  # :nodoc:
+module Sass::Constant
   class Number < Literal # :nodoc:
 
     attr_reader :unit

lib/sass/constant/operation.rb

@@ -1,8 +1,9 @@
 require 'sass/constant/string'
 require 'sass/constant/number'
 require 'sass/constant/color'
+require 'sass/constant/functions'
 
-module Sass::Constant # :nodoc:
+module Sass::Constant
   class Operation # :nodoc:
     def initialize(operand1, operand2, operator)
       @operand1 = operand1
@@ -18,10 +19,24 @@ module Sass::Constant # :nodoc:
       "(#{@operator.inspect} #{@operand1.inspect} #{@operand2.inspect})"
     end
 
+    def to_arglist
+      return [self] unless @operator == :comma
+      @operand1.to_arglist + @operand2.to_arglist
+    end
+
     protected
 
     def perform
       literal1 = @operand1.perform
+      if @operator == :funcall && Functions.public_instance_methods.include?(literal1.to_s) && literal1.to_s !~ /^__/
+        begin
+          return Functions.send(literal1.to_s, *@operand2.to_arglist)
+        rescue ArgumentError => e
+          raise e unless e.backtrace.first =~ /:in `#{literal1.to_s}'$/
+          raise Sass::SyntaxError.new("#{e.message} for `#{literal1.to_s}'")
+        end
+      end
+
       literal2 = @operand2.perform
       begin
         literal1.send(@operator, literal2)

lib/sass/constant/string.rb

@@ -1,6 +1,6 @@
 require 'sass/constant/literal'
 
-module Sass::Constant # :nodoc:
+module Sass::Constant
   class String < Literal # :nodoc:
 
     def parse(value)

test/sass/engine_test.rb

@@ -272,6 +272,20 @@ END
                  render("foo\n  +\n    bar\n      a: b\n    baz\n      c: d"))
   end
 
+  def test_functions
+    assert_equal("a {\n  b: #80ff80; }\n", render("a\n  b = hsl(120, 100%, 75%)"))
+    assert_equal("a {\n  b: #81ff81; }\n", render("a\n  b = hsl(120, 100%, 75%) + #010001"))
+  end
+
+  def test_argument_error
+    assert_raise(Sass::SyntaxError) { render("a\n  b = hsl(1)") }
+  end
+
+  def test_inaccessible_functions
+    assert_equal("a {\n  b: send(to_s); }\n", render("a\n  b = send(to_s)"))
+    assert_equal("a {\n  b: public_instance_methods(); }\n", render("a\n  b = public_instance_methods()"))
+  end
+
   private
 
   def render(sass, options = {})

test/sass/functions_test.rb

@@ -0,0 +1,51 @@
+require 'test/unit'
+require File.dirname(__FILE__) + '/../../lib/sass'
+require 'sass/constant'
+
+class SassFunctionTest < Test::Unit::TestCase
+  def test_hsl
+    # These tests adapted from the w3c browser tests
+    # http://www.w3.org/Style/CSS/Test/CSS3/Color/20070927/html4/t040204-hsl-h-rotating-b.htm
+    red = [255, 0, 0]
+    assert_rgb_hsl(red, [0, '100%', '50%'])
+    assert_rgb_hsl(red, [-360, '100%', '50%'])
+    assert_rgb_hsl(red, [360, '100%', '50%'])
+    assert_rgb_hsl(red, [6120, '100%', '50%'])
+
+    yellow = [255, 255, 0]
+    assert_rgb_hsl(yellow, [60, '100%', '50%'])
+    assert_rgb_hsl(yellow, [-300, '100%', '50%'])
+    assert_rgb_hsl(yellow, [420, '100%', '50%'])
+    assert_rgb_hsl(yellow, [-9660, '100%', '50%'])
+
+    green = [0, 255, 0]
+    assert_rgb_hsl(green, [120, '100%', '50%'])
+    assert_rgb_hsl(green, [-240, '100%', '50%'])
+    assert_rgb_hsl(green, [480, '100%', '50%'])
+    assert_rgb_hsl(green, [99840, '100%', '50%'])
+
+    cyan = [0, 255, 255]
+    assert_rgb_hsl(cyan, [180, '100%', '50%'])
+    assert_rgb_hsl(cyan, [-180, '100%', '50%'])
+    assert_rgb_hsl(cyan, [540, '100%', '50%'])
+    assert_rgb_hsl(cyan, [-900, '100%', '50%'])
+
+    blue = [0, 0, 255]
+    assert_rgb_hsl(blue, [240, '100%', '50%'])
+    assert_rgb_hsl(blue, [-120, '100%', '50%'])
+    assert_rgb_hsl(blue, [600, '100%', '50%'])
+    assert_rgb_hsl(blue, [-104880, '100%', '50%'])
+
+    purple = [255, 0, 255]
+    assert_rgb_hsl(purple, [300, '100%', '50%'])
+    assert_rgb_hsl(purple, [-60, '100%', '50%'])
+    assert_rgb_hsl(purple, [660, '100%', '50%'])
+    assert_rgb_hsl(purple, [2820, '100%', '50%'])
+  end
+
+  private
+
+  def assert_rgb_hsl(rgb, hsl)
+    assert_equal(rgb, Sass::Constant::Functions.hsl(*hsl.map(&Sass::Constant::Number.method(:new))).value)
+  end
+end