[orx-delegate-magic] Add more magic

orx-delegate-magic/src/commonMain/kotlin/difference/PropertyDifferencer.kt

@@ -0,0 +1,30 @@
+package difference
+
+import org.openrndr.Clock
+import kotlin.reflect.KProperty
+import kotlin.reflect.KProperty0
+
+class DoublePropertyDifferencer(
+    private val clock: Clock,
+    private val property: KProperty0<Double>,
+) {
+    private var lastValue: Double? = null
+    private var output: Double? = null
+    private var lastTime: Double? = null
+    operator fun getValue(any: Any?, property: KProperty<*>): Double {
+        if (lastTime != null) {
+            val dt = clock.seconds - lastTime!!
+            if (dt > 1E-10) {
+                output = this.property.get() - lastValue!!
+                lastValue = this.property.get()
+            }
+        } else {
+            lastValue = this.property.get()
+            output = lastValue!! - lastValue!!
+        }
+        lastTime = clock.seconds
+        return output ?: error("no value")
+    }
+}
+
+fun Clock.differencing(property: KProperty0<Double>) = DoublePropertyDifferencer(this, property)