Feature/425/easing functions (#426)

* (#425) Scale result of easing function by base speed to make its contribution noticeable

* (#425) Introduce watch mode for development and add ts-node for use with Typescript snippets during debugging

* (#425) Add enhancement to changelog

Author: s1hofmann

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 All notable changes to this project will be documented in this file.
 
+## @next
+- Enhancement: Scale easing function result by base speed before applying [(#425)](https://github.com/nut-tree/nut.js/issues/425)
+
 ## 2.2.0
 - Maintenance: Limit CI runs to PRs, not every push
 - Maintenance: Upgrade node version to 16 for all CI runs

lib/mouse-movement.function.spec.ts

@@ -64,7 +64,7 @@ describe("MovementType", () => {
             const mouseSpeed = 1000;
             const easingFunction: EasingFunction = (p: number) => {
                 if (p < 0.5) {
-                    return -0.5 * mouseSpeed;
+                    return -0.5;
                 }
                 return 0;
             };

lib/mouse-movement.function.ts

@@ -7,19 +7,22 @@ export interface EasingFunction {
     (progressPercentage: number): number;
 }
 
-export const calculateStepDuration = (speedInPixelsPerSecond: number) => (1 / speedInPixelsPerSecond) * 1_000_000_000;
+const nanoSecondsPerSecond = 1_000_000_000;
+
+export const calculateStepDuration = (speedInPixelsPerSecond: number) => (1 / speedInPixelsPerSecond) * nanoSecondsPerSecond;
 
 export const calculateMovementTimesteps = (
     amountOfSteps: number,
     speedInPixelsPerSecond: number,
     easingFunction: EasingFunction = linear
 ): number[] => {
+    const isEasingFunction = typeof easingFunction === "function";
     return Array(amountOfSteps)
         .fill(speedInPixelsPerSecond)
         .map((speed: number, idx: number) => {
             let speedInPixels = speed;
-            if (typeof easingFunction === "function") {
-                speedInPixels += easingFunction(idx / amountOfSteps);
+            if (isEasingFunction) {
+                speedInPixels += easingFunction(idx / amountOfSteps) * speedInPixels;
             }
             const stepDuration = calculateStepDuration(speedInPixels);
             return (isFinite(stepDuration) && stepDuration > 0) ? stepDuration : 0;