onScroll doesn't emit when user is scrolling

User scrolling is currently not emitted as an onScroll event. What’s the reason for this? Is this really intended? I’d like to monitor the scroll state of the terminal in order to notice when it’s scrolled all the way down, so I have to notice when the user is scrolling, which is not possible with the current behavior.

Details

• Browser and browser version: Firefox 84.0.1
• xterm.js version: 4.9.0

Steps to reproduce

1. attach event listener with terminal.onScroll()
2. scroll the terminal using the mouse

[Tyriar]

Looking over this change and re-reading the description, this seems more like a bug and I say we include it in a minor release. It looks like it might also fix an internal bug since this should clear when any user scroll happens:

https://github.com/schrej/xterm.js/blob/1925f1f442132919e109fdce21f6d30f8053c471/src/browser/Terminal.ts#L517-L517

I’ll leave the breaking change label to call it out in the release notes.

[daonb]

I need a onScrollBuffer, here’s my use case.

I’m developing a touchable terminal multiplexer where the user can use the cut gesture to split the pane. My app can split both right-to-left and top-to-bottom. When a user scrolls fast the latter is firing unintentionally.

To solve this I added code to disable vertical splitting for 2 seconds after the user scrolls. I’ve tried using onScroll in my code as according to the docs it does just what I need:

Adds an event listener for when a scroll occurs. The event value is the new position of the viewport.

The event doesn’t fire as expected and my panes keep splitting.