Add polygon method to dsl

Testing and documentation too.

Closes #67

lib/squib/api/shapes.rb

@@ -199,5 +199,30 @@ module Squib
       end
     end
 
+    # Draw a regular polygon at the given x,y
+    # @example
+    #   polygon x: 10, y: 10, n: 5, angle: Math::PI / 4, radius: 50,
+    #           fill_color: :green, stroke_color: :burgundy, :stroke_width: 3
+    #
+    # @option opts range [Enumerable, :all] (:all) the range of cards over which this will be rendered. See {file:README.md#Specifying_Ranges Specifying Ranges}
+    # @option opts x [Fixnum] (0) the x-coordinate of the center. Supports Unit Conversion, see {file:README.md#Units Units}.
+    # @option opts y [Fixnum] (0) the y-coordinate of the center. Supports Unit Conversion, see {file:README.md#Units Units}.
+    # @option opts n [Integer] (5) the number of points on the star
+    # @option opts angle [Fixnum] (0) the angle at which to rotate
+    # @option opts stroke_color [String] (:black) the color with which to stroke the line. See {file:README.md#Specifying_Colors___Gradients Specifying Colors & Gradients}.
+    # @option opts stroke_width [Decimal] (2.0) the width of the outside stroke. Supports Unit Conversion, see {file:README.md#Units Units}.
+    # @option opts fill_color [String] ('#0000') the color with which to fill the triangle. See {file:README.md#Specifying_Colors___Gradients Specifying Colors & Gradients}
+    # @option opts layout [String, Symbol] (nil) entry in the layout to use as defaults for this command. See {file:README.md#Custom_Layouts Custom Layouts}
+    # @return [nil] intended to be void
+    # @api public
+    def polygon(opts = {})
+      opts = needs(opts, [:range, :x, :y, :n, :circle_radius, :angle, :layout, :fill_color, :stroke_color, :stroke_width])
+      opts[:range].each do |i|
+        @cards[i].polygon(opts[:x][i], opts[:y][i], opts[:n][i], opts[:angle][i], opts[:radius][i],
+                        opts[:fill_color][i], opts[:stroke_color][i],
+                        opts[:stroke_width][i])
+      end
+    end
+
   end
 end

lib/squib/graphics/shapes.rb

@@ -109,13 +109,34 @@ module Squib
         cc.translate(x, y)
         cc.rotate(angle)
         cc.translate(-x, -y)
-        cc.move_to(x + outer_radius, y) #i = 0, so 
+        cc.move_to(x + outer_radius, y) #i = 0, so cos(0)=1 and sin(0)=0
         theta = Math::PI / n.to_f # i.e. (2*pi) / (2*n)
         0.upto(2 * n) do |i|
             radius = i.even? ? outer_radius : inner_radius
             cc.line_to(x + radius * Math::cos(i * theta),
                        y + radius * Math::sin(i * theta))
         end
+        cc.close_path
+        cc.set_source_squibcolor(stroke_color)
+        cc.set_line_width(stroke_width)
+        cc.fill_preserve
+        cc.set_source_squibcolor(fill_color)
+        cc.stroke
+      end
+    end
+
+    def polygon(x, y, n, angle, radius, fill_color, stroke_color, stroke_width)
+      use_cairo do |cc|
+        cc.translate(x, y)
+        cc.rotate(angle)
+        cc.translate(-x, -y)
+        cc.move_to(x + radius, y) # i = 0, so cos(0)=1 and sin(0)=0
+        theta = (2 * Math::PI) / n.to_f
+        0.upto(n) do |i|
+            cc.line_to(x + radius * Math::cos(i * theta),
+                       y + radius * Math::sin(i * theta))
+        end
+        cc.close_path
         cc.set_source_squibcolor(stroke_color)
         cc.set_line_width(stroke_width)
         cc.fill_preserve