ScrollView positioning when adding new elements on top of contents

As per short chat with @mortoray in Slack: I would want to be able to “keep the scrollview where it was” when adding new elements on top of its current contents.

Think of it how you pull-to-reload to load earlier messages in mobile apps, such as Slack, Messenger and others.

The contents of the ScrollView get populated at the top, but the scrollposition is set so that the “old” contents do not move (visually) when the “new” contents are added on top.

I’ve made an extra issue to cover this use-case and linked it to a group of ScrollView related features. I’m hoping to get around to working on these soon.