Implement lightning flashes

harrogate/src/halloween_2020.rs

@@ -1,27 +1,57 @@
 //! orange-and-purple with "lightning" flashes
 use super::delay;
 use house::{Harrogate, PORCH_BACK_LEN, PORCH_FRONT_LEN};
-use lights::{rgb::Rgb, HardwareRgb, Lights};
+use lights::{murmurf, rgb::Rgb, HardwareRgb, Lights};
 
 const BLACK: Rgb = Rgb(0, 0, 0);
+const LIGHTNING: Rgb = Rgb(255, 255, 220);
+
 const ORANGE: Rgb = Rgb(255, 150, 0);
 const PURPLE: Rgb = Rgb(100, 0, 128);
 
+// tenth of a second
+const TIC: u32 = 4_800_000;
+
 #[allow(dead_code)]
 #[inline(always)]
 pub fn run(lights: &mut impl Lights<Pixel = HardwareRgb>) -> ! {
-    let front_pattern = [PURPLE, ORANGE].iter().cycle().cloned();
-
-    let back_buffer = [BLACK; PORCH_BACK_LEN];
-
-    loop {
+    let mut rng = 0xB00u32;
+    let mut back_buffer = [BLACK; PORCH_BACK_LEN];
 
+    let mut draw = |back_buffer: &[Rgb]| {
+        let front_pattern = [PURPLE, ORANGE].iter().cycle().cloned();
         Harrogate {
-            porch_front: front_pattern.clone().take(PORCH_FRONT_LEN),
-            porch_back: back_buffer.iter().cloned()
+            porch_front: front_pattern.take(PORCH_FRONT_LEN),
+            porch_back: back_buffer.iter().cloned(),
         }
         .render_to(lights);
+    };
 
-        delay(12_000_000);
+    loop {
+        // clear
+        back_buffer.iter_mut().for_each(|pix| *pix = BLACK);
+        draw(&back_buffer);
+
+        // delay 4-20 seconds
+        delay(TIC * (murmurf(&mut rng) % 160 + 40));
+
+        // flash 1
+        flash(&mut rng, &mut back_buffer);
+        draw(&back_buffer);
+        delay(TIC);
+
+        // flash 2
+        flash(&mut rng, &mut back_buffer);
+        draw(&back_buffer);
+        delay(TIC * 2);
     }
 }
+
+fn flash(rng: &mut u32, back_buffer: &mut [Rgb]) {
+    let start = murmurf(rng) as usize % (PORCH_BACK_LEN - 20);
+    let len = murmurf(rng) as usize % 20 + murmurf(rng) as usize % 20 + 10;
+    let end = (start + len).min(PORCH_BACK_LEN);
+    back_buffer.as_mut()[start..end]
+        .iter_mut()
+        .for_each(|pix| *pix = LIGHTNING);
+}