Bug 483093

Summary: Add warning that enabling “Press left and right buttons for middle-click” would increase input latency
Product: [Applications] systemsettings Reporter: justus <justus2510>
Component: kcm_mouseAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED FIXED    
Severity: normal CC: fanzhuyifan, natalie_clarius, nate
Priority: NOR Keywords: junior-jobs, usability
Version First Reported In: 6.0.1   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: https://invent.kde.org/plasma/plasma-desktop/-/commit/b155f77b207f00c85e8344e6832ca8852001cf2c Version Fixed/Implemented In: 6.1
Sentry Crash Report:

Description justus 2024-03-10 10:30:14 UTC 
SUMMARY
If the “Press left and right buttons for middle-click” option is enabled, a very noticeable amount of latency gets added to mouse clicks. I can't say exactly how much it is, but fiddling around with reaction speed tests gives me a difference of somewhere around 40-60ms. If this is not fixable, there should at least be a warning, since this can have a big impact, especially for games.

STEPS TO REPRODUCE
1. Enable “Press left and right buttons for middle-click” option.

OBSERVED RESULT
Latency added to mouse clicks.

EXPECTED RESULT
No change in latency.
Comment 1 fanzhuyifan 2024-03-10 22:56:39 UTC 
I think the delay is inevitable -- we need to wait a bit to see if we are getting clicks from both buttons and emit a middle click.

With that said, a warning that this increases latency would be nice.
Comment 2 Nate Graham 2024-03-11 20:43:55 UTC 
Definitely a good junior job, yeah!
Comment 3 Bug Janitor Service 2024-03-18 21:16:30 UTC 
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-desktop/-/merge_requests/2129
Comment 4 Nate Graham 2024-03-21 18:36:35 UTC 
Git commit b155f77b207f00c85e8344e6832ca8852001cf2c by Nate Graham, on behalf of Wladimir Leuschner.
Committed on 21/03/2024 at 18:36.
Pushed by ngraham into branch 'master'.

kcms/{mouse,touchpad} Mention that middle button emulation increases latency

Add a ContextualHelpButton to the middle mouse click emulation option that
informs the user that activating this option increases the click latency.
FIXED-IN: 6.1

M  +25   -17   kcms/mouse/kcm/libinput/main.qml
M  +25   -19   kcms/mouse/kcm/libinput/main_deviceless.qml
M  +30   -23   kcms/touchpad/kcm/libinput/touchpad.qml

https://invent.kde.org/plasma/plasma-desktop/-/commit/b155f77b207f00c85e8344e6832ca8852001cf2c