link programs before getting uniform locations; add Widget#draw_rect; fix GL.draw_rect; store uniforms as GLint

runtime/lib/gl_program.rb

@@ -16,6 +16,7 @@ class GLProgram
         raise NotImplementedError.new("Other arguments not yet implemented")
       end
     end
+    link
     options.each do |option, value|
       case option
       when :uniforms
@@ -26,6 +27,5 @@ class GLProgram
         raise "Unknown option #{option.inspect}"
       end
     end
-    link
   end
 end

runtime/lib/widget.rb

@@ -30,4 +30,8 @@ module Widget
 
   def render_end
   end
+
+  def draw_rect(x, y, width, height, r, g, b, a)
+    GL.draw_rect(@x + x, @y + y, width, height, r, g, b, a)
+  end
 end