working

build.rs

@@ -5,10 +5,16 @@ use image::{GenericImageView, ImageReader};
 
 // Example custom build script.
 fn main() {
-    println!("cargo::rerun-if-changed=assets/*");
     println!("cargo::rerun-if-changed=build.rs");
 
-    let img = ImageReader::open("src/assets/cat.png")
+    handle_image("cat");
+    handle_image("meow");
+}
+
+fn handle_image(name: &str) {
+    println!("cargo::rerun-if-changed=src/assets/{name}.png");
+
+    let img = ImageReader::open(format!("src/assets/{name}.png"))
         .unwrap()
         .decode()
         .unwrap();
@@ -33,6 +39,6 @@ fn main() {
 
     let out_dir = env::var("OUT_DIR").unwrap();
 
-    let mut f = File::create(Path::new(&out_dir).join("cat.bin")).unwrap();
+    let mut f = File::create(Path::new(&out_dir).join(format!("{name}.bin"))).unwrap();
     f.write_all(&out.as_raw_slice()).unwrap();
 }

src/lib.rs

 use bitvec::{order::Msb0, view::BitView};
 
-const WIDTH: usize = 96;
-//const HEIGHT: usize = 38;
+const WIDTH: i32 = 96;
+const HEIGHT: i32 = 38;
 
 #[no_mangle]
 pub extern "C" fn next_frame(frame: u16, ptr: *mut u8) -> u8 {
@@ -12,19 +12,40 @@ pub extern "C" fn next_frame(frame: u16, ptr: *mut u8) -> u8 {
     }
 
     let cat = include_bytes!(concat!(env!("OUT_DIR"), "/cat.bin")).view_bits::<Msb0>();
+    let meow = include_bytes!(concat!(env!("OUT_DIR"), "/meow.bin")).view_bits::<Msb0>();
+
+    let thres = WIDTH / 4;
+
+    let dx = (frame as i32 * 4 - thres).min(thres);
 
     for x in 0..96 {
         for y in 0..38 {
             let out_idx = index(x, y);
-            let in_idx = index((x - frame as usize * 4) % WIDTH, y);
+            let in_idx = index(x - dx, y);
 
             out.set(out_idx, cat[in_idx]);
         }
     }
 
+    if dx == thres && frame / 7 % 2 == 0 {
+        // make meow flash on and off every 4 frames for the remaining time
+
+        for x in 0..96 {
+            for y in 0..38 {
+                let idx = index(x, y);
+
+                out.set(idx, meow[idx] || out[idx]);
+            }
+        }
+    }
+
     0
 }
 
-fn index(x: usize, y: usize) -> usize {
-    x + y * WIDTH
+fn index(x: i32, y: i32) -> usize {
+    if x < 0 || y < 0 || x >= WIDTH || y >= HEIGHT {
+        return 0;
+    }
+
+    x as usize + y as usize * WIDTH as usize
 }