Commands that fill a non-full buffer lock up the terminal for a couple of seconds

[Tyriar]

Perhaps we can prefill/warm up the buffer in a better way?

Steps to reproduce

1. Run yes

VS Code issue: microsoft/vscode#42234

[Tyriar]

Until the buffer is full, calls to syncScrollArea are triggering tonnes of refresh calls.

So it looks like this is related to the scroll bar changing (as in #132) which we avoid now when the buffer is full since the scrollbar does not change as the buffer size and scroll position don't change.

[Tyriar]

Here's what the non-full buffer syncScrollArea looks like zoomed in:

[Tyriar]

There's a recursive loop which eventually resolves as terminal data keeps coming in:

1. Terminal.write
2. Terminal scroll event
3. Viewport.syncScrollArea
4. Viewport.refresh
5. (repeats from 2)

[Tyriar]

Minimal repro: printf 'y%.0s\n' {1..1000}

[Tyriar]

It's only recursive because the lines keep changing, refresh should be rate limited.

[Tyriar]

Need to redo the PR as there was an issue and it was reverted (#463), the commit is on 444_rate_limit_viewport_refresh

[Tyriar]

This is still an issue and a fix would probably involve a custom scroll bar which I'm not sure we want to commit to just yet.

[Tyriar]

This is actually only a problem with the way that the attach addon works, as it continually reads in data before the data is parsed.