focus line pushed

[shaozi]

When a user's cursor is on a line, say line 100, and another user insert lines before that, the user's view will be pushed down. Normally this is not an issue, but when the other user insert a lot of lines, the first user's focused line will be pushed out of the bottom of the view.

It should maintain the view to make sure the focused line for each user does not jump / shift. By adjust the scroll position of the view. So no matter what other user editing, each user will not see jump of lines.

[DerMolly]

Maybe we should implement it so, that by default you follow your own cursor (see #281)