[virtualizer] Size changes should not result in item updates

[vursen]

Description

Follow-up to #7205

Currently, virtualizer size changes trigger an update for every visible item in the viewport and sometimes even for those that are outside. This update is unnecessary because the change of the list size cannot affect the content of the list items.

Expected outcome

The updateElement function should not be invoked on size change.

Minimal reproducible example

<script type="module" src="./common.js"></script>
<script type="module">
  import { Virtualizer } from '@vaadin/component-base/src/virtualizer.js';

  const scrollTarget = document.querySelector('#scroll-target');
  const scrollContainer = document.querySelector('#scroll-container');

  const virtualizer = new Virtualizer({
    createElements: (count) => [...Array(count)].map(() => document.createElement('div')),
    updateElement: (el, index) => {
      console.warn('updateElement', index);
      el.style.left = '0';
      el.style.right = '0';
      el.style.display = 'flex';
      el.style.alignItems = 'center';
      el.style.background = index % 2 === 0 ? '#DCDCDC' : '#C0C0C0';
      el.style.height = '30';
      el.style.padding = '0 10px';
      el.textContent = `Item ${index}`;
    },
    scrollTarget,
    scrollContainer,
  });

  virtualizer.size = 100000;

  const decreaseSizeButton = document.querySelector('.decrease-size');
  decreaseSizeButton.addEventListener('click', () => {
    virtualizer.size = 50000;
  });

  const increaseSizeButton = document.querySelector('.increase-size');
  increaseSizeButton.addEventListener('click', () => {
    virtualizer.size = 150000;
  });
</script>

<button class="decrease-size">Decrease size</button>

<button class="increase-size">Increase size</button>

<div style="height: 400px;" id="scroll-target">
  <div id="scroll-container"></div>
</div>

Steps to reproduce

1. Scroll the list a bit down
2. Click "Increase size" and see updateElement messages in the console log.
3. Click "Decrease size" and see updateElement messages in the console log.

Environment

Vaadin version(s): 24.4
OS:

Browsers

No response

[vursen]

The update appears to be associated with the scroll restoration in the size setter.