Bug 465299

Summary:	Add option to disable smooth/high-resolution scrolling in kcm_mouse
Product:	[Applications] systemsettings	Reporter:	David G. <david>
Component:	kcm_mouse	Assignee:	Plasma Bugs List <plasma-bugs>
Status:	RESOLVED DUPLICATE
Severity:	wishlist	CC:	david, john, nate, xnagytibor
Priority:	NOR
Version:	5.26.90
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description David G. 2023-02-05 03:02:10 UTC

SUMMARY
5.26.90 (5.27 beta) has added libinput 1.19 smooth/high-resolution scrolling to the Plasma Wayland session.

This is a welcome addition, however it cannot be configured, and it is an issue:
1: Users may dislike this feature.
2: in games (e.g. Minecraft, scrolling through items in the hotbar becomes unreliable due to scroll interpolation or Counter Strike: Global Offensive, where the same applies to the weapon selector)

There should be an option to easily disable this feature within kcm_mouse. libinput allows for configuring this feature, so it should be possible.

STEPS TO REPRODUCE
1. Start a Plasma Wayland session.
2. Open System Settings
3. Navigate to Input Devices > Mouse
4. Observe options
5. Navigate to Workspace Behavior > General Behavior
6. Observe options

OBSERVED RESULT
There is no option to disable smooth/high resolution scrolling, per mouse or system-wide.

EXPECTED RESULT
There should ideally be an option to disable smooth/high resolution scrolling, both per mouse and system-wide.

SOFTWARE/OS VERSIONS
Linux: Arch Linux vanilla kernel 6.1.9-arch1-1
KDE Plasma Version: 5.26.90
KDE Frameworks Version: 5.102.0
Qt Version: 5.15.8

ADDITIONAL INFORMATION
KDE Plasma Wayland session.

Comment 1 Nagy Tibor 2023-02-05 03:27:32 UTC

Also affects the X11 session on Neon.

This smooth scrolling change broke the following things for me:
- Scrolling over the volume slider in Elisa.
- Scrolling over the volume applet on the system tray.
- Scrolling over comboboxes started skipping over several items.

I had to add the following libinput local override to make scrolling usable again:

[Logitech M705 Marathon Mouse]
MatchVendor=0x046D
MatchName=Logitech M705
AttrEventCodeDisable=REL_WHEEL_HI_RES;

Comment 2 Nagy Tibor 2023-02-05 04:12:40 UTC

Some more details about how this broke my volume controls because I realized it might not be obvious:

With these high resolution scrolling changes one or two ratchet clicks of wheel rotation started going from 0% straight to 100% of volume. Previously with low-res scrolling this took 20 ratchet clicks. It also introduced constant scroll twitching that was suppressed before by low resolution scrolling.

Comment 3 David G. 2023-02-05 05:37:33 UTC

It appears the weird behavior of high resolution scrolling in games is a due to Bug 464776, which has been fixed in a commit (https://invent.kde.org/plasma/kwin/-/commit/9f494da9fa29fd2a8abd34e5bde95d531026301e) right after the beta was tagged.

Comment 4 David G. 2023-02-05 05:40:03 UTC

Actually, if I understand correctly, the fixed bug would also affect other clients that expect low resolution scrolling, like the volume sliders you mentioned.

Comment 5 John Brooks 2023-02-06 23:10:52 UTC

I think everything described here (scrolling in games, the volume control) is due to that fixed bug.

*** This bug has been marked as a duplicate of bug 464776 ***

Comment 6 Nate Graham 2023-02-06 23:12:50 UTC

I had a feeling too, but couldn't find it. Thanks, John!