Add totalSize props to VirtualScroller to support lazy loading

[nclemeur]

[x] feature request 

It would be good to have a totalSize props (or similar) on the virtual loader that can be used to calculate the lazy loading parameters. Currently, the length of the items is used for that purpose (in the getLast method) but this is not really adapted when using lazily loaded data.

[loancarre]

hello, it would be nice to have this

[AlaaL]

This is very important feature, I want to use lazy load to load new chunk of data every time i reach the end of scroller, and i cannot do that without loading the entire data at first in the items so the virtual scroller can know how many items there are to load.
It kina break the concept of lay loading.

[BenJackGill]

Lazy loading wont let me scroll down until it "lazy loads" the full data set. It just keeps flashing the first items in the array. Only when the list is fully loaded does it actually scroll down.

I assume it's because of this problem.

Has anyone found a workaround for this? This issue was raised in 2021 so it it seems they're not giving this issue priority

[BenJackGill]

Current workaround: Do not use the loading prop. Just use lazy and the matching @lazy-load emit.

If using the loading prop there will be the problem that we can't scroll down until the full list is loaded. Without that prop it almost works.

The only problem now is that if a user quickly scrolls to the very bottom then the loading to stop right there. It's like they 'catch the bottom' and it will only continue loading more if they scroll back up a little more to release it and let it know there are more items to load.

[github-actions]

Due to PrimeTek's demanding roadmap for PrimeVue and the limited bandwidth of the core team, this issue is available for anyone to work on. Make sure to reference this issue in your pull request. ✨ Thank you for your contribution! ✨