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_mouse	Assignee:	Plasma Bugs List <plasma-bugs>
Status:	RESOLVED FIXED
Severity:	normal	CC:	fanzhuyifan, natalie_clarius, nate
Priority:	NOR	Keywords:	junior-jobs, usability
Version:	6.0.1
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:	https://invent.kde.org/plasma/plasma-desktop/-/commit/b155f77b207f00c85e8344e6832ca8852001cf2c	Version Fixed In:	6.1

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