nits

src/buffer.rs

@@ -11,7 +11,7 @@ impl Buf {
     }
 
     // Truncate x and y and return a corresponding index into the data slice.
-    fn index(&self, x: f32, y: f32) -> usize {
+    const fn index(&self, x: f32, y: f32) -> usize {
         // x/y can come in negative, hence we shift them by width/height.
         let i = (x + self.width as f32) as usize & (self.width - 1);
         let j = (y + self.height as f32) as usize & (self.height - 1);