Bug 430532

Summary:	Vertical scrolling broken for input devices with horizontal scrolling component (e.g. touchpad, trackpoint)
Product:	[Applications] dolphin	Reporter:	mantapeppe
Component:	view-engine: general	Assignee:	Dolphin Bug Assignee <dolphin-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	kfm-devel, nate, nxtv2.0
Priority:	NOR	Keywords:	regression
Version:	20.11.80
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:	https://invent.kde.org/system/dolphin/commit/303740c68af83f45be1bdea56a250397a83efa6a	Version Fixed In:	20.12.1
Attachments:	Compare angleDelta().x() and angleDelta().y() to determine scroll direction

Description mantapeppe 2020-12-18 10:25:55 UTC

Scrolling in a vertical direction with a touchpad is stuttery and doesn't maintain scroll inertia unless the movement is perfectly vertical. The bug is not present when using Dolphin 20.08.3; on my Arch install the issue appeared on version 20.12.0, but a build of version 20.11.80 from git contains the bug as well.

Steps to reproduce:
1. Install any Dolphin version >= 20.11.80 on a laptop
2. Open a directory with a long list of files
3. Scroll using the touchpad/trackpoint

Expected result: smooth scrolling that maintains inertia

Observed result: scrolling stops as soon as scrolling movement is not perfectly vertical


Additional information:
I believe the bug might be similar in nature to a Konsole bug reported a few months ago as the expected and observed behaviour are pretty much the same; the bug in question is

https://bugs.kde.org/show_bug.cgi?id=425765

Comment 1 Nate Graham 2020-12-18 17:38:18 UTC

Works for me with my trackpad. Are you using libinput or synaptics drivers?

Comment 2 mantapeppe 2020-12-18 18:06:23 UTC

Synaptics, but I'll try to check using libinput as well.

Comment 3 mantapeppe 2020-12-19 19:19:27 UTC

Scrolling using libinput works as expected, although scroll inertia is not preserved (I used the default libinput config so it might be because of that)

Comment 4 Nate Graham 2020-12-19 19:21:37 UTC

Sounds like it's a bug in the Synaptics drivers.

Unfortunately scroll inertia is not built into Libinput. Its developer believes, not unreasonably, that this is a feature the toolkit should handle, as doing it in the driver causes some unfixable bugs in apps. And sadly Qt is not great about supporting it in its scrollviews.

Comment 5 mantapeppe 2020-12-22 22:01:29 UTC

Created attachment 134272 [details]
Compare angleDelta().x() and angleDelta().y() to determine scroll direction

(In reply to Nate Graham from comment #4)
> Sounds like it's a bug in the Synaptics drivers.

Turns out it actually was a Dolphin bug... It's exactly the same as the Konsole one: assuming that a scroll event with and angleDelta().x() != 0 is definitely not a vertical scroll.

Applying this patch fixes the issue

Comment 6 mantapeppe 2020-12-22 22:35:29 UTC

Sent a merge request to the repo, guess I'll change the status of this bug to "fixed"

Merge request: https://invent.kde.org/system/dolphin/-/merge_requests/149

Comment 7 Nate Graham 2020-12-22 22:40:54 UTC

Not fixed until the merge request is merged. :)

Thanks for submitting it!

Comment 8 mantapeppe 2020-12-23 18:39:37 UTC

Git commit 303740c68af83f45be1bdea56a250397a83efa6a by Eduard Manta.
Committed on 23/12/2020 at 16:17.
Pushed by ngraham into branch 'release/20.12'.

Fix vertical scroll with horizontal component not being recognized properly

a scroll that includes an horizontal component != 0 might still be a vertical scroll

M  +2    -2    src/kitemviews/kitemlistcontainer.cpp

https://invent.kde.org/system/dolphin/commit/303740c68af83f45be1bdea56a250397a83efa6a

Comment 9 Nate Graham 2021-01-12 17:04:02 UTC

*** Bug 431410 has been marked as a duplicate of this bug. ***

Comment 10 Nate Graham 2021-01-12 17:23:50 UTC

*** Bug 431410 has been marked as a duplicate of this bug. ***