switch to using a generic rect

src/main.rs

@@ -23,9 +23,7 @@ struct Model {
     engine: PhysicsEngine,
 }
 
-fn random_vec(_app: &App) -> nalgebra::Vector2<f32> {
-    let boundary = _app.window_rect();
-
+fn random_vec_in_rect(boundary: &Rect) -> nalgebra::Vector2<f32> {
     let x = random_range(-100., 100.);
     let y = random_range(-150., boundary.top());
 
@@ -36,13 +34,15 @@ fn fill_particles(app: &App, colliders: &mut ColliderSet, bodies: &mut RigidBody
     // Keeping track of already placed balls to avoid overlap
     // Need to look into a way to do this with rapier directly
     let mut positions: Vec<nalgebra::Vector2<f32>> = Vec::new();
+    let boundary = &app.window_rect();
+
     for _ in 0..PARTICLE_COUNT {
-        let mut xy = random_vec(app);
+        let mut xy = random_vec_in_rect(boundary);
         while !positions
             .iter()
             .all(|pos| pos.metric_distance(&xy) > PARTICLE_SIZE * 2.)
         {
-            xy = random_vec(app)
+            xy = random_vec_in_rect(boundary)
         }
         positions.push(xy);