cleanup Buf struct

src/buffer.rs

@@ -1,13 +1,17 @@
 #[derive(Debug, Clone)]
 pub struct Buf {
-    pub width: usize,
-    pub height: usize,
+    width: usize,
+    height: usize,
     pub buf: Vec<f32>,
 }
 
 impl Buf {
-    pub const fn new(width: usize, height: usize, buf: Vec<f32>) -> Self {
-        Buf { width, height, buf }
+    pub fn new(width: usize, height: usize) -> Self {
+        Buf {
+            width,
+            height,
+            buf: vec![0.0; height * width],
+        }
     }
 
     // Truncate x and y and return a corresponding index into the data slice.