Linux tmux: scrolling distance with the mouse wheel

[ownia]

I'm using tmux with mouse mode enabled, and noticed that the scroll distance differs before and after tmux is activated. I tried mouse-scroll-multiplier, but it affects the global configuration instead of just taking effect on tmux. I want to reduce the scroll speed of tmux without affecting ghostty, is there a good solution for this issue?

	Ghostty	Ghostty with tmux	Ghostty (mouse-scroll-multiplier=1)	Ghostty with tmux (mouse-scroll-multiplier=1)
pane scroll	3 lines per tick	first is 10, then 15 lines per tick	1 lines per tick	5 lines per tick
vim scroll	9 lines per tick	9 lines per tick	3 lines per tick	3 lines per tick
less --mouse	3 lines per tick	3 lines per tick	1 lines per tick	1 lines per tick

tmux conf has:

set -g mouse on

vimrc has:

set mouse=a
set ttymouse=sgr

[ownia]

I think I've found the root cause. It's probably due to the precision scroll and SGR Mouse (DECSET 1006). I'll consider submitting a fix later.

[pgattic]

I am experiencing a similar issue in Neovim with both a standard Dell mouse and my laptop's touchpad. Ghostty's scrolling behavior (on Linux at least) is different from Kitty, Alacritty, and Foot.

Lines scrolled per wheel tick:

Terminal program	Ghostty (default)	Ghostty with mouse-scroll-multiplier = 1	Kitty	Alacritty	Foot
None/shell (pane scroll)	3	1	5*	3	3
Neovim	9	3	3	3	3
Neovim with vim.opt.mousescroll = "ver:1,hor:1"	3	1	1	1	1

• After setting wheel_scroll_multiplier 3.0 in my kitty config (it uses 5.0 as the default), Kitty yields the exact same line scrolling behavior as the other terminals in this test.

Also, modifying the "scroll multiplier" option in the other terminal emulators does not affect Neovim's scroll speed, while it does in Ghostty.

Just going by the data here, it seems to me that Ghostty might be sending additional scroll interrupts corresponding to the number in mouse-scroll-multiplier to TUI apps, while the correct behavior is to only send one per wheel tick, and let the TUI app handle scroll distance itself.

All testing done on NixOS with nixos-unstable, in a Wayland environment.