Bug 504133 - Middle Button Scroll breaking expected mouse behaviour in apps
Summary: Middle Button Scroll breaking expected mouse behaviour in apps
Status: RESOLVED DUPLICATE of bug 504010
Alias: None
Product: plasmashell
Classification: Plasma
Component: general (other bugs)
Version First Reported In: 6.2.5
Platform: SteamOS Linux
: NOR normal
Target Milestone: 1.0
Assignee: Plasma Bugs List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-05-13 06:30 UTC by Karin Engström
Modified: 2025-05-13 15:31 UTC (History)
2 users (show)

See Also:
Latest Commit:
Version Fixed/Implemented In:
Sentry Crash Report:


Attachments
Smooth panning > setting enabled > slammed into the lowest zoom possible (1.58 MB, image/jpeg)
2025-05-13 06:30 UTC, Karin Engström
Details

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Description Karin Engström 2025-05-13 06:30:48 UTC
Created attachment 181235 [details]
Smooth panning > setting enabled > slammed into the lowest zoom possible

Hi! I searched for middle scroll and didn't see this issue come up.

I just updated to the opt-in for Steam Deck to access new Plasma 6 settings like this mouse option and am encountering technical issues with the implementation. The mouse behaviour on Linux is a concern for trying to get more into a non-Windows system (I don't see a usecase for the pasting, myself, as I like the clear control of CTRL-C CTRL-V & usually just end up pasting random nonsense strings into Discord by mistake previously).

KDE Plasma is a lucky and appealing first choice in that regard, as your design philosophy goes against the common hostility I've seen elsewhere from people used to using their computers a different way.
Thanks for working on implementing an option for this common preference outside long-time Linux users!

SUMMARY
The [Press middle button and move to scroll] setting introduced in Plasma 6 breaks navigating video games, as it overrides basic camera controls. This override of apps is universal, as can be seen in also replacing the click-scroll of Firefox (no directional box showing up in the clicked location anymore). Upon testing I see it also breaks panning around your workspace in apps such as GIMP. A general issue with the setting.

STEPS TO REPRODUCE
1. Middle-click and pan around normally.
2. Enable the setting in [Mouse & Touchpad]
3. The OS now overrides game controls and doesn't let you pan the camera at all.

OBSERVED RESULT
Instead of smoothly going along with your mouse movements as desired, it freezes up in place and frenetically zooms in and out on the exact spot your mouse was.

EXPECTED RESULT
Not overriding how the mouse is meant to be used in a given application. Without taking these into account the only remedy would be to open System Settings for the mouse every time you were to use a different application. Discord? Open it and enable. Game? Open it and disable. And so forth.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: SteamOS 3.7.6 Build: 20250510.100
KDE Plasma Version: 6.2.5
KDE Frameworks Version: 6.9.0
Qt Version: 6.8.1
Comment 1 Bug Janitor Service 2025-05-13 06:33:40 UTC
Thank you for the bug report!

However Plasma 6.2.5 is no longer eligible for support or maintenance from KDE; supported versions are 5.27. (LTS), and 6.3 (non-LTS) or newer. Please upgrade to a supported version as soon as your distribution makes it available to you. Plasma is a fast-moving project, and bugs in one version are often fixed in the next one.

If you need support for Plasma 6.2.5, please contact your distribution, who bears the responsibility of providing support for older releases that are no longer supported by KDE.

If you can reproduce the issue after upgrading to a supported version, feel free to re-open this bug report.
Comment 2 Karin Engström 2025-05-13 06:41:03 UTC
I don't see anything that would make me believe that versions past what SteamOS uses has fixed this? Will anyone see this post or is this just a bot autodeletion?
Comment 3 Karin Engström 2025-05-13 06:48:24 UTC
(For clarity, I did look through other patch notes and the references to scroll that came up were about Touch Controls. If it's improper to bring up regardless, I don't really see the point of the submission process having options for other versions.)
Comment 4 cwo 2025-05-13 08:27:02 UTC
Older versions are an option because I don't think bugzilla allows us to disable them entirely. Pre-6.3 versions are no longer supported by KDE at this point (except for 5.27, which is technically still the active LTS release, but practically has no further releases planned), so a bot closes them automatically. 

The on-button scrolling function is intended primarily for particular kinds of devices, mostly Thinkpad-style pointing sticks and possibly finger trackballs, where they're there to emulate a scroll wheel. This is an upstream libinput option, we're just allowing users to enable it as they see fit. It literally replaces pointer movements with scrolling events, and this is the point of the option. That this breaks middle-button dragging is documented and intended upstream behavior - it's there to trade middle-button dragging for scroll-wheel emulation, something  that users of some pointing devices (typically without a scroll wheel or other built-in scrolling function) are accustomed to.  For more information on this function, see here: https://wayland.freedesktop.org/libinput/doc/latest/scrolling.html#on-button-scrolling 

We should probably add some helper text that informs users of this tradeoff. I'll try to get it in before 6.4 string freeze this week.

There are two feature requests to allow toggling the function with a key binding (bug 504011), and on a per-app/window basis (bug 504010). I'm marking this as a duplicate of the second one, but from your description I guess what you really want is Windows-style auto-scrolling, which is tracked in bug 439610. Feel free to subscribe to that report if you're interested in this feature.

*** This bug has been marked as a duplicate of bug 504010 ***
Comment 5 Bug Janitor Service 2025-05-13 09:11:16 UTC
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-desktop/-/merge_requests/2994
Comment 6 cwo 2025-05-13 15:31:36 UTC
Git commit 5e0134f563476ddc5326f07f3ce056b16594cfca by Christoph Wolk.
Committed on 13/05/2025 at 15:31.
Pushed by cwo into branch 'master'.

kcms/mouse: add ContextualHelpButton for on-button scrolling

Since Plasma 6.2, we allow users to toggle the libinput on-button
scrolling option from the mouse kcm. This function is intended for
scroll-wheel emulation on devices that do not have one, such as pointing
sticks, although some users may enjoy it on other devices as well. Users
often come looking for something more akin to Windows' auto-scrolling
feature, which we do not support. This leads to confusion, as its
behavior is substantially different from the feature they are looking
for, and there are significant downsides for some applications to having
this enabled (as it disables all middle-click dragging functionality).

Let's add a helper button that makes clear (a) what the downside of
enabling this option is and (b) what it is primarily intended for, so
users don't think it's a botched implementation of auto-scroll.


Co-authored-by: Nate Graham <nate@kde.org>

M  +20   -11   kcms/mouse/ui/main.qml

https://invent.kde.org/plasma/plasma-desktop/-/commit/5e0134f563476ddc5326f07f3ce056b16594cfca