Implemented mouse config

[NeoTheFox]

Add two options:
mouse_mod - sets a linear acceleration for the emulated mouse
invert_scroll - inverts the scrolling direction for the emulated mouse

Hopefully it helps to make the pointer more consistent across multiple devices.

Previously discussed in #339

[feschber]

There is one more thing:

Since we are making changes to the configuration, we should think about the names a bit more.
I'd prefer these options to be under a different section and name them a bit differently like this:

# transformations applied to input events received from other devices
[event_post_processing]
mouse_sensitivity = 1.0
invert_scroll = true

This would later enable a similar section for event pre transformations (when being sent to other devices):

# transformations applied to input events sent to other devices
[event_pre_processing]
mouse_sensitivity = 1.0
# linear_acceleration_factor = 1.2
# scroll_sensitivity = 0.3
invert_scroll = false

Maybe you can come up with some better names, but I find mouse_mod a bit indescriptive and would prefer sensitivity here.

[feschber]

Maybe input_post_processing would be a better name.

[NeoTheFox]

Wouldn't a simple input suffice?

[feschber]

Not if we want to add pre processing later on

[NeoTheFox]

That's fair. Done and done.

[NeoTheFox]

A note on my formatter - my cargo version is
cargo 1.90.0 (840b83a10 2025-07-30) (Arch Linux rust 1:1.90.0-4.1)
If the linter is mandatory I implore you to consider adding a clear .rustfmt.toml to the repository, as my version sees no issues here and forces the problematic line into that format.

[feschber]

A note on my formatter - my cargo version is cargo 1.90.0 (840b83a10 2025-07-30) (Arch Linux rust 1:1.90.0-4.1) If the linter is mandatory I implore you to consider adding a clear .rustfmt.toml to the repository, as my version sees no issues here and forces the problematic line into that format.

I have the same version and it did complain about the formatting when running cargo fmt --check.

Would you mind opening a separate PR for the rust-fmt.toml (I'm not against that)

[feschber]

Ah one last thing: The input_post_processing section in the config should also be optional, not just the individual settings.

[feschber]

Oh (in case you are unaware): The dynamic updates to the sensitivity and scrolling inversion do not work. You are passing the values to the EmulationProxy but not from there to the actual input-emulation.

[feschber]

If you don't want to do it, I can fix it myself as well.

[NeoTheFox]

I'll probably only be able to get back to this on the weekends, so if it's a quick fix - up to you. I'll do it myself in a few days otherwise