Cinnamon: mouse acceleration slider changes mouse speed, not mouse acceleration

[TrickMe]

Linux Mint 19.2

Hey guys!

Did anyone realize yet that custom acceleration in mouse options actually effects the mouse speed / mouse sensitivity?
Custom sensitivity has no effect at all!

Is it just me or is there something mixed up?

[pyroxar]

How model of your mouse you use? Custom acceleration work for me very well.

[TrickMe]

How model of your mouse you use? Custom acceleration work for me very well.

I've tried different mice on multiple distributions.
Maybe you have the feeling that mouse acceleration is working for you, but actually mouse sensitivity is used to set the mouse speed, not mouse acceleration:
https://en.wikipedia.org/wiki/Computer_mouse
"The computer industry often measures mouse sensitivity in terms of counts per inch (CPI), commonly expressed as dots per inch (DPI)"

Mouse acceleration commonly should be used to increase the cursor speed according to the speed
the mouse is moved.
If you move the mouse quickly, the cursor should move further than if you move the mouse by the same amount slowly.
"Current software can change the speed of the cursor dynamically, taking into account the mouse's absolute speed..."

I've explained this issue to the libinput repository page yesterday, but my issue was deleted.

[TrickMe]

Here also a quick video that explains what mouse acceleration is supposed to do:
https://www.youtube.com/watch?v=SZCvUGY2DY0 from start to about 1:50

The acceleration implementation in CS:GO sucks, but there is a very simple, fast and easy way of implementing it correctly, I also posted an issue in the libinput repository, explaining the calculations:

accelerationFactor = pow(sqrt(rawInputFPx * rawInputFPx + rawInputFPy * rawInputFPy) * ( Sensitivity / time )), acceleration)

outputx = (rawInputFPx * sensitivity) * accelerationFactor
outputy = (rawInputFPy * sensitivity) * accelerationFactor

I know it's not code, but I'm not a programmer. I just did the math behind it.
For more (very extensive) detail (boundaries, typing, etc.), check the 9th comment in https://gitlab.freedesktop.org/libinput/libinput/issues/205

[damian101]

I also have the issue that the mouse sensitivity setting doesn't change anything (#8808), but changing the mouse acceleration works as expected. When the slider is on the far left, then no pointer acceleration is applied, and pointer acceleration gets increased when you move the slider to the right. @TrickMe, can you check if that's the case for you? If it is, then this issue should be closed.
The pointer will move faster when more acceleration is applied, but that doesn't mean that the slider changes the sensitivity, because changing sensitivity shouldn't change the pointer acceleration at all.

[TrickMe]

The pointer will move faster when more acceleration is applied...

But mouse acceleration is not supposed to make the pointer move faster, mouse sensitivity is.
That's my whole point!

I've made a demo to visually show the correct use of acceleration using my algorithm shown in my last post:

Accel_test2.zip
Just hold left mouse and drag the pointer around.
The sprite moves with applied acceleration and sensitivity.
It moves slower than the pointer when moved slowly, but faster than the pointer when moved fast, if acceleration is set > 0. Transition from slower to faster is seamless.
If sensitivity is 1 and acceleration is 0, the sprite will stick with the pointer.

press ESC to exit the demo.

edit:
updated to Accel_test version 2 with in app sensitivity and acceleration control.
please notice that the sensitivity slider is logarithmic. It's more practical and it doesn't need 0 anyway I think.
Have fun playing around with it everyone. Check it out!

[damian101]

@TrickMe I think I see what you mean, but the title is misleading. It makes it sound as if the acceleration slider would change mouse sensitivity (and nothing else) on your system.
Very nice demo btw.

[TrickMe]

@damian101 Thank you.
I've tested acceleration on Linux mint, Manjaro Xfce, KDE and Cinnamon edition with Logitech G 700 and Logitech G MX518.
It seems to me that the acceleration slider indeed just and only changes the mouse speed, aka sensitivity.
There is no acceleration taking place, no matter how far I drag the acceleration slider to the right.

[damian101]

@TrickMe Oh, seems like we misunderstood each other.
The mouse settings behaviour on your system is really weird. For all my systems it is like described in issue #8808. I also had a laptop where both sliders had no effect, but that was the exception.
All my laptops have a trackpoint, maybe that's the difference?

[TrickMe]

@damian101 As stated in the title, I'm referring to the mouse settings.
With the touchpad on my laptop, sensitivity does not work either, but that's a different issue with probably a different cause.

Libinput, the input library used with cinnamon, treats mice, touchpads and trackpoints differently and has it's own profile for each. Therefor, issues with one device type does not necessarily effect others.

[damian101]

@TrickMe Ok, I don't know much about libinput.
Just to make it clear: I'm also only talking about settings for the mouse.

[TrickMe]

@damian101 I changed the title to avoid confusion, but I'm still not clear what your attention is.
I have the feeling you are trying to tell me that the mouse acceleration slider of cinnamon changes the mouse acceleration, which is clearly not the case.
If the purpose of mouse acceleration is unclear to you, start my demo again, move the sliders and see what it's supposed to do.
I stick to the meaning of the title, because it points out the issue accurately.

If I misunderstood you, please line out clearly what you are trying to tell me, because I don't get it.

[damian101]

@TrickMe The acceleration slider correctly changes mouse/pointer acceleration on all my systems. I understand that this slider changes speed/sensitivity on your system instead.
I justed wanted to make sure in the beginning that you really mean speed/sensitivity by mouse speed, and not acceleration, because some desktop environments like GNOME actually name their mouse acceleration slider "Mouse Speed".