maybe fix

src/engine.rs

@@ -144,7 +144,7 @@ impl Game {
         })
     }
 
-    pub fn run(mut self) {
+    pub fn run<F: Fn(&mut Context) -> ()>(mut self, f: F) {
         'running: loop {
             for event in self.event_pump.poll_iter() {
                 match event {
@@ -156,6 +156,9 @@ impl Game {
                     _ => {}
                 }
             }
+            self.canvas.set_draw_color(Color::RGB(60, 180, 180));
+            self.canvas.clear();
+            f(&mut self.context());
             self.canvas.present();
         }
         self.canvas.present();

src/main.rs

@@ -12,7 +12,7 @@ impl<'a> Component for Player<'a> {}
 struct PlayerRenderer;
 
 impl System for PlayerRenderer {
-    fn on_add(&self, ctx: &mut engine::Context) {}
+    fn on_add(&self, _ctx: &mut engine::Context) {}
 
     fn on_update(&self, _ctx: &mut engine::Context) {}
 }
@@ -24,10 +24,10 @@ fn main() {
         let mut context = game.context();
         context.add_system(Box::new(PlayerRenderer));
         context.spawn(vec![Box::new(Player { sprite: None })]);
+    }
 
+    game.run(|context| {
         let sprite = context.load_sprite("textures/player.png").unwrap();
         context.draw_sprite(&sprite, 16, 16).unwrap();
-    }
-
-    game.run();
+    });
 }