Add support for Sass Color types

lib/sassc/native/native_functions_api.rb

@@ -17,6 +17,9 @@ module Native
     attach_function :sass_make_string, [:string], :sass_value_ptr
 
 
+    # ADDAPI union Sass_Value* ADDCALL sass_make_color   (double r, double g, double b, double a);
+    attach_function :sass_make_color, [:double, :double, :double, :double], :sass_value_ptr
+
     # ADDAPI enum Sass_Tag ADDCALL sass_value_get_tag (const union Sass_Value* v);
     attach_function :sass_value_get_tag, [:sass_value_ptr], SassTag
     attach_function :sass_value_is_null, [:sass_value_ptr], :bool

lib/sassc/script/color.rb

@@ -4,7 +4,7 @@ module SassC
   module Script
     class Color < ::Sass::Script::Value::Color
       def to_native
-        Native::make_string(to_s)
+        Native::make_color(red, green, blue, alpha)
       end
     end
   end

test/functions_test.rb

@@ -53,6 +53,18 @@ def test_function_with_no_return_value
       EOS
     end
 
+    def test_function_that_returns_a_color
+      engine = Engine.new(<<-SCSS)
+div {
+  background: returns-a-color(); }
+      SCSS
+
+      assert_equal <<-EXPECTED_SCSS, engine.render
+div {
+  background: black; }
+      EXPECTED_SCSS
+    end
+
     def test_function_with_optional_arguments
       engine = Engine.new("div {url: optional_arguments('first'); url: optional_arguments('second', 'qux')}")
       assert_equal <<-EOS, engine.render
@@ -137,6 +149,10 @@ def nice_color_argument(color)
         return Script::String.new(color.to_s, :string)
       end
 
+      def returns_a_color()
+        return Script::Color.new(red: 0, green: 0, blue: 0)
+      end
+
       module Compass
         def stylesheet_path(path)
           Script::String.new("/css/#{path.value}", :identifier)