From 19c1bc16cbc6725463890382365203824b7fd353 Mon Sep 17 00:00:00 2001
From: Liam DeBeasi <liamdebeasi@users.noreply.github.com>
Date: Wed, 13 Mar 2024 15:57:30 -0400
Subject: [PATCH] fix(datetime): wheel picker shows consistently in overlays
 (#29147)

Issue number: resolves #26234

---------

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issue. -->

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

We use an IntersectionObserver to know when each picker column is
visible so we can properly scroll the active option in each column into
view. The IO callback passes an array of entries. Up until this PR, we
have always grabbed the first entry in the array. The problem is that
browsers will sometimes group multiple events into a single array. This
means it's possible to have an event with `isIntersecting: false` and
then another event with `isIntersecting: true` in the same callback.
Since we always grabbed the first event we did not account for the
instances where events were coalesced.

This resulted in column options sometimes not scrolling into view when
presented via an overlay.

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- Picker column now grabs the last event in the entries array. This
represents the most recent threshold change.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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  2. Update the BREAKING.md file with the breaking change.
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## Other information

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screenshots of how the component looks before and after the change. -->

Dev build: `7.7.5-dev.11710347256.1954cae9`
---
 .../picker-column-internal/picker-column-internal.tsx       | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/core/src/components/picker-column-internal/picker-column-internal.tsx b/core/src/components/picker-column-internal/picker-column-internal.tsx
index 73b8dd34356..401c67c95af 100644
--- a/core/src/components/picker-column-internal/picker-column-internal.tsx
+++ b/core/src/components/picker-column-internal/picker-column-internal.tsx
@@ -92,7 +92,11 @@ export class PickerColumnInternal implements ComponentInterface {
    */
   componentWillLoad() {
     const visibleCallback = (entries: IntersectionObserverEntry[]) => {
-      const ev = entries[0];
+      /**
+       * Browsers will sometimes group multiple IO events into a single callback.
+       * As a result, we want to grab the last/most recent event in case there are multiple events.
+       */
+      const ev = entries[entries.length - 1];
 
       if (ev.isIntersecting) {
         const { activeItem, el } = this;