Virtual Scrolling stalls when scrolling via keyboard with large set of complex data

[s73obrien]

Bug, feature request, or proposal: Bug

What is the expected behavior?

When scrolling down the list by holding down the up or down arrow key, the list should scroll smoothly all the way down to the end

What is the current behavior?

When scrolling down the list by holding down the up or down arrow key, at random times and seemingly random circumstances, the scrolling behavior stalls. I believe the focus is being lost on the list for whatever reason as, if you click on the list and press the arrow key, scrolling resumes as normal.

What are the steps to reproduce?

StackBlitz here. Click on the list and press and hold the down arrow key. It may take a couple attempts, but eventually it should stall.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Reproduced in Chrome 71.0.3578.98 and IE 11. Could not reproduce in Firefox 64.0.

Package	Version
@angular/animations	7.2.0
@angular/cdk	7.2.1
@angular/common	7.2.0
@angular/compiler	7.2.0
@angular/core	7.2.0
@angular/forms	7.2.0
@angular/http	7.2.0
@angular/material	7.2.1
@angular/platform-browser	7.2.0
@angular/platform-browser-dynamic	7.2.0
@angular/router	7.2.0
core-js	2.6.1
rxjs	6.3.3
rxjs-compat	6.3.3
zone.js	0.8.26

Is there anything else we should know?

Resource-bound maybe?

[mmalerba]

I am able to reproduce this. It seems like maybe the element that was clicked on originally is destroyed and then the scrolling stalls. Clicking inside the viewport again will make it work again

[KimAlexander]

Any ideas or workaround ?

[afluegge]

Having the same problem. Any progress on this?

Reproduced in Chrome 80.0.3987.122 (Official Build) (64-bit)

Package	Version
@angular/animations	7.2.16
@angular/cdk	7.3.7
@angular/common	7.2.16
@angular/compiler	7.2.16
@angular/core	7.2.16
@angular/forms	7.2.16
@angular/material	7.3.7
@angular/platform-browser	7.2.16
@angular/platform-browser-dynamic	7.2.16
@angular/router	7.2.16
core-js	2.6.5
rxjs	6.5.3
rxjs-compat	6.4.0
zone.js	0.8.29

[s73obrien]

I ended up rewriting a part of the virtual scrolling lib into what I was working on at the time. I don't remember which changes I made exactly, but they are in this directory -> s73obrien/ngx-hex-input/projects/ngx-hex-input/src/lib/scrolling

[renkei]

Workround for me: Don't click into the viewport, e.g. a table. Instead, click on the scrollbar. As long as the scrollbar has focus you can use down/page down and up/page up without issues.