Put ArmedNotches back in the wheel module

Trimming the dialog helper out of the copied module took the stray-notch guard
with it, because the two sit next to each other in the file the other apps
carry, and the module stopped compiling. It is the part that makes the first
notch after a pause do nothing, so the wheel cannot be nudged by a thumb
resting on it.

Author: gi-os

examples/LightNYCSubway/src/main/kotlin/com/thelightphone/subway/hw/Wheel.kt

@@ -140,6 +140,46 @@ fun WheelScroll(state: ScrollableState, active: Boolean = true) {
     }
 }
 
+/**
+ * Notches, minus the stray ones. See [ARM_NOTCHES].
+ *
+ * Armed state lives in the effect rather than in composition state: it is a property of the
+ * turn in progress, and a recomposition mid-turn should not disarm the wheel.
+ */
+@Composable
+private fun ArmedNotches(active: Boolean, onNotch: (Int) -> Unit) {
+    val handler by rememberUpdatedState(onNotch)
+    val bus = LocalWheelBus.current ?: return
+    LaunchedEffect(bus, active) {
+        if (!active) return@LaunchedEffect
+        var armed = false
+        var held = 0
+        var count = 0
+        var last = 0L
+        bus.notches.collect { notches ->
+            val now = System.nanoTime() / 1_000_000
+            if (now - last > IDLE_MS) {
+                armed = false
+                held = 0
+                count = 0
+            }
+            last = now
+            if (armed) {
+                handler(notches)
+                return@collect
+            }
+            held += notches
+            count++
+            if (count >= ARM_NOTCHES) {
+                armed = true
+                // Release what the guard was holding, so nothing deliberate is lost.
+                if (held != 0) handler(held) else handler(notches.sign)
+                held = 0
+            }
+        }
+    }
+}
+
 /**
  * Distance still owed to the scroller.
  *