bug(cdk-virtual-scroll-viewport): Does not work with ngZoneRunCoalescing

[andershessellund]

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

cdk-virtual-scroll-viewport does not work with ngZoneRunCoalescing enabled. Some frames are rendered with incorrect content, causing visual "glitches".

Reproduction

Steps to reproduce:

1. Go to https://stackblitz.com/edit/cdk-virtual-scroll-bug-run-coalescing
2. Scroll . The bug is most apparent when scrolling slowly.

Expected Behavior

All rendered frames has correct content during scrolling.

Actual Behavior

Some frames are rendered with incorrect content, causing glitches.

Environment

• Angular: 14.2.6
• CDK/Material: 14.2.5
• Browser(s): Safari, Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): iOS, macOS

[stasberkov]

Guys, please fix this. It has bad visual effect. Our product (and any other) with this glitch looks very unprofessional.

[VitalyVoroshilov]

We also have user complaints (flicking) about big list virtual scrolling. Can you please advise?

[stasberkov]

This nasty visual glitch goes away if using custom scrolling strategy like this

export class CustomVirtualScrollStrategy extends FixedSizeVirtualScrollStrategy {
    constructor() {
        super(60, 250, 500);
    }

    override onContentScrolled(): void {
        setTimeout(() => super.onContentScrolled(), DEFAULT_SCROLL_TIME);
    }
}