How to align the messages in StreamMessageListView on top?

[zzunebye]

I would like messages to appear from the top of the screen when the height of the existing messages combined with header is less than the allowed area of the StreamMessageListView.

By default, the new messages in the new chatroom appears from the bottom.

I've tried setting initialAlignment parameter to 1.0, which actually achieves what I desire, but when the user send a new message, the alignment is reset to the position where initialAlignment: 0.0 would make.

What we desire to have:

After sending new message:

Thank you for your help in advance!