MouseScrollUp/MouseScrollDown — mouse wheel events for TUI apps that can target specific co-ordinates

[mikecsmith]

Hi — I recently built a TUI tool using BubbleTea (thanks!) that uses MouseModeCellMotion to scroll content when the mouse wheel is over a given panel.

I used vhs to record some demos but found that ScrollUp/ScrollDown don't provide a way to target a specific position on screen, so I couldn't scroll a particular panel in my TUI and couldn't get the scrolling smooth enough via 1 line scrolling key press events.

I've taken a stab at fixing this by dispatching synthetic WheelEvents on the xterm screen element with cell-based coordinates, so apps listening for SGR mouse input receive the scroll. The proposed syntax is:

MouseScrollDown 5 @100,20   # 5 scroll events at column 100, row 20
MouseScrollUp 3              # coordinates default to center if omitted

Scroll behaviour is configurable via two new settings:

Set MouseScrollLines 3       # lines per scroll event (default: 1)
Set MouseScrollDelay 100ms   # delay between repeats (default: 30ms)

Before I open a PR, I wanted to check:

• Are you open to this feature in general?
• Would you prefer the current approach (separate MouseScrollUp/MouseScrollDown commands), or would it be cleaner to fold this into the existing ScrollUp/ScrollDown — e.g. by sending mouse wheel events when @col,row coordinates are provided and falling back to viewport scrolling when they're not?

Happy to adjust the approach based on your preference.

Thanks,
Mike

Diff of implementation: mikecsmith@4e5e302

Video showing it in action:

scroll-variant-d.mp4