Add movement wrapping for cells

src/main.rs

@@ -42,7 +42,7 @@ fn main() {
     let canvas = Rc::new(RefCell::new(canvas));
 
     let main_loop = move || {
-
+        let mut moved = false;
         for event in ctx.borrow_mut().event_pump().unwrap().poll_iter() {
             match event {
                 Event::Quit { .. }
@@ -59,15 +59,19 @@ fn main() {
                     match key {
                         Keycode::Left => {
                             rect.borrow_mut().x -= 10;
+                            moved = true;
                         }
                         Keycode::Right => {
                             rect.borrow_mut().x += 10;
+                            moved = true;
                         }
                         Keycode::Up => {
                             rect.borrow_mut().y -= 10;
+                            moved = true;
                         }
                         Keycode::Down => {
                             rect.borrow_mut().y += 10;
+                            moved = true;
                         }
                         _ => {}
                     }
@@ -76,11 +80,27 @@ fn main() {
             }
         }
 
+        // Handle wrapping at the edges
+        if moved {
+            let mut rect = rect.borrow_mut();
+            let canvas_size = canvas.borrow().window().size();
+            if rect.x < 0 {
+                rect.x = canvas_size.0 as i32 - rect.width() as i32;
+            } else if rect.x >= 640 {
+                rect.x = 0;
+            }
+            if rect.y < 0 {
+                rect.y = canvas_size.1 as i32 - rect.height() as i32;
+            } else if rect.y >= canvas_size.1 as i32 {
+                rect.y = 0;
+            }
+        }
+
         let mut canvas = canvas.borrow_mut();
         canvas.set_draw_color(BLACK);
         canvas.clear();
         canvas.set_draw_color(WHITE);
-        canvas.fill_rect(rect.borrow().clone());
+        canvas.fill_rect(rect.borrow().clone()).expect("could not draw rectangle");
         canvas.present();
     };