fix(pixel): clean up scroll depth implementation (SDK-136)

- Rename above_fold → aboveFold for consistency with all other
  autocapture event properties (camelCase convention)
- Remove dead aboveFold parameter from checkAndFire — it was always
  false after the dwell timer got its own inline path
- Remove deprecated window.pageYOffset fallback — all supported
  browsers (Chrome 80+) have window.scrollY

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: bkbooth

packages/audience/pixel/README.md

@@ -85,7 +85,7 @@ All events fire automatically with no instrumentation required.
 | `session_end` | Page unload (`visibilitychange` / `pagehide`) | `sessionId`, `duration` (seconds) |
 | `form_submitted` | HTML form submission | `formAction`, `formId`, `formName`, `fieldNames`. `emailHash` at `full` consent only. |
 | `link_clicked` | Outbound link click (external domains only) | `linkUrl`, `linkText`, `elementId`, `outbound: true` |
-| `scroll_depth` | Scroll milestone reached (25%, 50%, 75%, 90%, 100%) | `depth` (integer). On above-the-fold pages (no scroll possible), fires `depth: 100` with `above_fold: true` after a 2-second dwell. |
+| `scroll_depth` | Scroll milestone reached (25%, 50%, 75%, 90%, 100%) | `depth` (integer). On above-the-fold pages (no scroll possible), fires `depth: 100` with `aboveFold: true` after a 2-second dwell. |
 
 ### Disabling specific auto-capture
 

packages/audience/pixel/src/autocapture.test.ts

@@ -680,15 +680,15 @@ describe('autocapture', () => {
         expect(enqueue).toHaveBeenCalledTimes(5);
       });
 
-      it('does not include above_fold property on scrollable pages', () => {
+      it('does not include aboveFold property on scrollable pages', () => {
         setup({ scroll: true });
 
         (window as Record<string, unknown>).scrollY = 375;
         window.dispatchEvent(new Event('scroll'));
         flushRAF();
 
         expect(enqueue.mock.calls[0][1]).toEqual({ depth: 25 });
-        expect(enqueue.mock.calls[0][1]).not.toHaveProperty('above_fold');
+        expect(enqueue.mock.calls[0][1]).not.toHaveProperty('aboveFold');
       });
 
       it('does not fire at consent none', () => {
@@ -740,7 +740,7 @@ describe('autocapture', () => {
         jest.useRealTimers();
       });
 
-      it('fires scroll_depth 100 with above_fold after dwell time', () => {
+      it('fires scroll_depth 100 with aboveFold after dwell time', () => {
         setup({ scroll: true });
 
         // Should NOT fire immediately
@@ -751,7 +751,7 @@ describe('autocapture', () => {
 
         expect(enqueue).toHaveBeenCalledWith('scroll_depth', {
           depth: 100,
-          above_fold: true,
+          aboveFold: true,
         });
         expect(enqueue).toHaveBeenCalledTimes(1);
       });

packages/audience/pixel/src/autocapture.ts

@@ -71,7 +71,7 @@ function getScrollPercent(): number {
   const { scrollHeight, clientHeight } = document.documentElement;
   if (scrollHeight <= clientHeight) return 100;
   const scrollable = scrollHeight - clientHeight;
-  return Math.min(100, Math.round(((window.scrollY || window.pageYOffset) / scrollable) * 100));
+  return Math.min(100, Math.round((window.scrollY / scrollable) * 100));
 }
 
 /**
@@ -91,17 +91,15 @@ function setupScrollTracking(
   let rafId = 0;
   let dwellTimer: ReturnType<typeof setTimeout> | null = null;
 
-  const checkAndFire = (aboveFold: boolean): void => {
+  const checkAndFire = (): void => {
     if (!canTrack(getConsent())) return;
 
     const pct = getScrollPercent();
     for (let i = 0; i < SCROLL_MILESTONES.length; i++) {
       const milestone = SCROLL_MILESTONES[i];
       if (pct >= milestone && !fired.has(milestone)) {
         fired.add(milestone);
-        const properties: Record<string, unknown> = { depth: milestone };
-        if (aboveFold) properties.above_fold = true;
-        enqueue('scroll_depth', properties);
+        enqueue('scroll_depth', { depth: milestone });
       }
     }
   };
@@ -117,12 +115,12 @@ function setupScrollTracking(
       if (!canTrack(getConsent())) return;
       if (!fired.has(100)) {
         fired.add(100);
-        enqueue('scroll_depth', { depth: 100, above_fold: true });
+        enqueue('scroll_depth', { depth: 100, aboveFold: true });
       }
     }, ABOVE_FOLD_DWELL_MS);
   } else {
     // Check initial scroll position (e.g. anchor links, restored scroll).
-    checkAndFire(false);
+    checkAndFire();
   }
 
   // Scroll listener (handles both scrollable pages and pages that become
@@ -131,7 +129,7 @@ function setupScrollTracking(
     if (rafId) return; // Already scheduled
     rafId = requestAnimationFrame(() => {
       rafId = 0;
-      checkAndFire(false);
+      checkAndFire();
     });
   };