diff --git a/runtime/lib/widget.rb b/runtime/lib/widget.rb
index ac775c3..aebdd61 100644
--- a/runtime/lib/widget.rb
+++ b/runtime/lib/widget.rb
@@ -18,7 +18,7 @@ module Widget
   end
 
   def draw
-    if @x > 0 and @y > 0
+    if @width > 0 and @height > 0
       render_begin
       render
       children.each do |child|
diff --git a/src/Window.cc b/src/Window.cc
index 4ccdd28..b9c4501 100644
--- a/src/Window.cc
+++ b/src/Window.cc
@@ -82,6 +82,22 @@ static void Window_free(void * ptr)
     delete window;
 }
 
+static void resize()
+{
+    GLint viewport_size[2];
+    Window * window;
+    Data_Get_Struct(window_instance, Window, window);
+    SDL_GetWindowSize(window->sdl_window, &viewport_size[0], &viewport_size[1]);
+    glViewport(0, 0, viewport_size[0], viewport_size[1]);
+    rb_funcall(window_instance,
+               rb_intern("resize"),
+               4,
+               INT2FIX(0),
+               INT2FIX(0),
+               INT2FIX(viewport_size[0]),
+               INT2FIX(viewport_size[1]));
+}
+
 static VALUE Window_new(VALUE klass)
 {
     static bool one_created = false;
@@ -117,21 +133,18 @@ static VALUE Window_new(VALUE klass)
     one_created = true;
 
     VALUE rv = Data_Wrap_Struct(ruby_class, NULL, Window_free, window);
-    rb_obj_call_init(rv, 0, NULL);
     /* TODO: remove window_instance and map SDL_Window * to Window Ruby object
      * to support multiple windows. */
     window_instance = rv;
+    rb_obj_call_init(rv, 0, NULL);
+    resize();
 
     return rv;
 }
 
-static void resize()
+static void draw()
 {
-    GLint viewport_size[2];
-    Window * window;
-    Data_Get_Struct(window_instance, Window, window);
-    SDL_GetWindowSize(window->sdl_window, &viewport_size[0], &viewport_size[1]);
-    glViewport(0, 0, viewport_size[0], viewport_size[1]);
+    rb_funcall(window_instance, rb_intern("draw"), 0);
 }
 
 static VALUE Window_event_loop(VALUE klass)
@@ -152,11 +165,11 @@ static VALUE Window_event_loop(VALUE klass)
             switch (event.window.event)
             {
             case SDL_WINDOWEVENT_EXPOSED:
-//                draw();
+                draw();
                 break;
             case SDL_WINDOWEVENT_RESIZED:
                 resize();
-//                draw();
+                draw();
                 break;
             }
         }
@@ -165,9 +178,28 @@ static VALUE Window_event_loop(VALUE klass)
     return Qnil;
 }
 
+static VALUE Window_render(VALUE self)
+{
+    glClearColor (0.0, 0.0, 0.0, 0.0);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    return Qnil;
+}
+
+static VALUE Window_render_end(VALUE self)
+{
+    Window * window;
+    Data_Get_Struct(window_instance, Window, window);
+    SDL_GL_SwapWindow(window->sdl_window);
+
+    return Qnil;
+}
+
 void Window_Init(void)
 {
     ruby_class = rb_define_class("Window", rb_cObject);
     rb_define_singleton_method(ruby_class, "new", (VALUE(*)(...))Window_new, 0);
     rb_define_singleton_method(ruby_class, "event_loop", (VALUE(*)(...))Window_event_loop, 0);
+    rb_define_method(ruby_class, "render", (VALUE(*)(...))Window_render, 0);
+    rb_define_method(ruby_class, "render_end", (VALUE(*)(...))Window_render_end, 0);
 }