Bug 354482 - scrolling quickly with the mouse wheel jumps and can even scroll backwards
Summary: scrolling quickly with the mouse wheel jumps and can even scroll backwards
Status: RESOLVED MOVED
Alias: None
Product: kate
Classification: Applications
Component: application (show other bugs)
Version: 5.0.0
Platform: Fedora RPMs Linux
: NOR normal
Target Milestone: ---
Assignee: KWrite Developers
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2015-10-28 04:14 UTC by jozxyqk
Modified: 2016-09-07 19:18 UTC (History)
10 users (show)

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Description jozxyqk 2015-10-28 04:14:05 UTC 
Scrolling can be quite jumpy. The faster you scroll, the more likely it is that the scroll goes in the wrong direction. Seems to happen more consistently while the window is not in focus.


Reproducible: Sometimes

Steps to Reproduce:
1. open any document long enough that it can be scrolled
2. change the focus to another window
3. spin the mouse wheel quite fast, as though you're headed at least a page away and not just a line or two
Comment 1 Martin Klapetek 2015-10-28 15:29:25 UTC 
Seen that as well. This is only with mouse scrolling though, I cannot reproduce with touchpad.
Comment 2 Iryna 2015-11-11 13:33:55 UTC 
Continuously getting this problem on VirtualBox machine with Ubuntu 15.04 (x64) and Kate 5.0.0 installed.
Comment 3 Denis Akimkin 2016-01-28 16:45:32 UTC 
The problem seems to be not only Kate-specific. For example, I was able to reproduce that in Dolphin when scrolling through a dir with a lot of entries.

There's a Qt5 bug (https://bugreports.qt.io/browse/QTBUG-46461) describing somewhat similar behaviour, but I'm not sure whether it's really related to this bug. The test case from Qt bug seems to produce wrong angle delta regardless to whether window is in focus or not.
Comment 4 Tsu Jan 2016-02-02 23:20:31 UTC 
I encountered this erratic and annoying behavior since Qt-5.3. In https://bugreports.qt.io/browse/QTBUG-38274, they say it's fixed but it isn't. As far as I know, the problem is in the first QWheelEvent after the enter event.

I think a clean Qt bug report is needed. Otherwise, it might not be fixed soon.
Comment 5 Tsu Jan 2016-02-02 23:28:34 UTC 
I forgot to confirm what Denis said: this is a Qt5 bug and not specific to Kate or KDE. However, it is specific to Linux.
Comment 6 Bob Wya 2016-03-18 15:57:25 UTC 
Unlike KDE-4 I've got to remember to give Qt 5 applications explicit mouse focus before scrolling in them...

I don't see what's hard about reproducing this Qt 5 bug... It occurs every time that I mouse over a scrollable region, in a Qt 5 application, and I don't give that Window explicit focus (by giving it a LHS mouse button event)!! It's really annoying... :-(
Comment 7 Christian 2016-04-26 09:58:58 UTC 
I'm observing a similar behaviour. I have to mention that I'm running Ubuntu in VirtualBox. However my problem does not appear in any other application like for example Firefox.

Scrolling with the mouse wheel is very laggy/jumpy and only works at all if the mouse is not moved at all. No such problem can be observed when using the touchpad.

Same problem in KWrite by the way and similar but less severe also in gedit but not at all (everything 100% smooth, no matter how hard you shake the mouse) in Firefox.
Comment 8 Aurelijus 2016-06-17 18:08:59 UTC 
Still around on Kubuntu 16.04 with backported KDE 5.6 (same was true with 5.5).
Comment 9 Tsu Jan 2016-06-17 18:34:18 UTC 
I'm almost sure that this bug is about https://bugreports.qt.io/browse/QTBUG-49294
Comment 10 Buovjaga 2016-07-10 11:23:32 UTC 
Status should obviously be confirmed by now, so changing. What would be a better product for this?
Comment 11 Christoph Cullmann 2016-09-07 19:18:24 UTC 
I think the Qt Bugtracker is ok for that, I close this as moved, please comment there, as it needs to be fixed in Qt.