improve touchscreen scrolling on carousel

src/components/tech-stack-carousel/tech-stack-carousel.ts

@@ -26,9 +26,12 @@ export class TechStackCarousel implements AfterViewInit, OnDestroy {
   private currentAutoScrollSpeedPxPerSecond = 0;
   private targetAutoScrollSpeedPxPerSecond = 0;
   private isPausePendingStop = false;
+  private isTouchInteracting = false;
+  private isProgrammaticScrollUpdate = false;
   private readonly autoScrollSpeedPxPerSecond = 72;
   private readonly speedRampDurationMs = 420;
   private readonly speedStopThresholdPxPerSecond = 0.5;
+  private readonly touchScrollResumeDelayMs = 1200;
   isAutoScrolling = false;
   showLeftFade = false;
   showRightFade = false;
@@ -89,9 +92,34 @@ export class TechStackCarousel implements AfterViewInit, OnDestroy {
   }
 
   onCarouselScroll(): void {
+    if (this.isProgrammaticScrollUpdate) {
+      this.isProgrammaticScrollUpdate = false;
+      this.updateFadeState();
+      return;
+    }
+
+    // Keep autoscroll from fighting touch/momentum scrolling on mobile.
+    this.pauseAutoScrollImmediately();
+    this.scheduleResume(this.touchScrollResumeDelayMs);
     this.updateFadeState();
   }
 
+  onTouchStart(): void {
+    this.isTouchInteracting = true;
+    this.clearScheduledResume();
+    this.pauseAutoScrollImmediately();
+  }
+
+  onTouchEnd(): void {
+    this.isTouchInteracting = false;
+    this.scheduleResume(this.touchScrollResumeDelayMs);
+  }
+
+  onTouchCancel(): void {
+    this.isTouchInteracting = false;
+    this.scheduleResume(this.touchScrollResumeDelayMs);
+  }
+
   onHoverStart(): void {
     this.pauseAutoScroll();
     this.clearScheduledResume();
@@ -118,6 +146,11 @@ export class TechStackCarousel implements AfterViewInit, OnDestroy {
   }
 
   resumeAutoScroll(): void {
+    if (this.isTouchInteracting) {
+      this.scheduleResume(this.touchScrollResumeDelayMs);
+      return;
+    }
+
     this.isPausePendingStop = false;
     this.targetAutoScrollSpeedPxPerSecond = this.autoScrollSpeedPxPerSecond;
     this.syncAutoScrollState();
@@ -242,6 +275,7 @@ export class TechStackCarousel implements AfterViewInit, OnDestroy {
     // Normalize only when moving past the duplicated track boundary to avoid abrupt remaps on quick re-entry.
     this.virtualScrollLeft = nextVirtualScrollLeft >= loopWidth ? nextVirtualScrollLeft - loopWidth : nextVirtualScrollLeft;
 
+    this.isProgrammaticScrollUpdate = true;
     carousel.scrollLeft = this.virtualScrollLeft;
   }
 
@@ -277,5 +311,20 @@ export class TechStackCarousel implements AfterViewInit, OnDestroy {
       this.targetAutoScrollSpeedPxPerSecond > this.speedStopThresholdPxPerSecond ||
       this.currentAutoScrollSpeedPxPerSecond > this.speedStopThresholdPxPerSecond;
   }
+
+  private pauseAutoScrollImmediately(): void {
+    this.clearScheduledResume();
+
+    if (this.autoScrollFrameId !== null) {
+      cancelAnimationFrame(this.autoScrollFrameId);
+      this.autoScrollFrameId = null;
+    }
+
+    this.isPausePendingStop = false;
+    this.currentAutoScrollSpeedPxPerSecond = 0;
+    this.targetAutoScrollSpeedPxPerSecond = 0;
+    this.lastAutoScrollTime = 0;
+    this.syncAutoScrollState();
+  }
 }