refactoring sprite class

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    compass (0.11.beta.2.994cf53)
+    compass (0.11.beta.2.995a20c)
       chunky_png (~> 0.12.0)
       sass (>= 3.1.0.alpha.218)
 

lib/compass/sass_extensions/functions/sprites.rb

@@ -19,38 +19,32 @@ module Compass::SassExtensions::Functions::Sprites
     # collects image sizes and input parameters for each sprite
     def compute_image_metadata!
       @width = 0
+      init_images
+      compute_image_positions!
+      @height = @images.last.top + @images.last.height
+    end
     
+    def init_images
       @images = image_names.collect do |relative_file|
         image = Compass::SassExtensions::Sprites::Image.new(relative_file, options)
         @width = [ @width, image.width + image.offset ].max
         image
       end
+    end
     
+    def compute_image_positions!
       @images.each_with_index do |image, index|
-        if index == 0
-          image.top = 0
-        else
-          last_image = @images[index-1]
-          image.top = last_image.top + last_image.height + [image.spacing,  last_image.spacing].max
-        end
-        if image.position.unit_str == "%"
-          image.left = (@width - image.width) * (image.position.value / 100)
-        else
-          image.left = image.position.value
-        end
+        image.left = image.position.unit_str == "%" ? (@width - image.width) * (image.position.value / 100) : image.position.value
+        next if index == 0
+        last_image = @images[index-1]
+        image.top = last_image.top + last_image.height + [image.spacing,  last_image.spacing].max
       end
-      @height = @images.last.top + @images.last.height
     end
 
     def image_for(name)
       @images.detect { |img| img.name == name}
     end
 
-    # Calculate the size of the sprite
-    def size
-      [width, height]
-    end
-
     def require_png_library!
       begin
         require 'oily_png'

lib/compass/sass_extensions/sprites/base.rb

@@ -27,6 +27,11 @@ module Compass
           compute_image_metadata!
         end
 
+        # Calculate the size of the sprite
+        def size
+          [width, height]
+        end
+
         def sprite_names
           image_names.map{|f| Compass::Sprites.sprite_name(f) }
         end

lib/compass/sass_extensions/sprites/image.rb

@@ -9,6 +9,7 @@ module Compass
 
         def initialize(relative_file, options)
           @relative_file, @options = relative_file, options
+          @left = @top = 0
         end
 
         def file