Created attachment 110368 [details] Desmonstrative screen recording When scrolling in okular, it normally goes well. However, the only (annoying) exception is that when I scroll using my touchpad, sometimes okular jumps "randomly" first and then it scrolls normalls from where it has jumped to. After some observation and experienment, I have pinned down the situation where this happens and the behaviour: 0. It only happens when I'm using touchpad to scroll, and only in okular (as far as I have observed); 1. It only happens when my cursor moves from outside of okular application frame (e.g. move to title bar, or a kde panel, or another application) to inside of okular application frame; The toolbar is considered as "inside"; 2. The "randomly" jumping isn't really random: it is always "several lines" "down" (about half a page in most documents); 3. The jumping happens immediately (without annimation); 4. After the jump, okular scrolls normally at the position where it has jumped to. Sometimes, okular continues jumping even after the first jump and the cursor is not moved outside of okular. Closing okular can "solve" this problem. The attachment is a screen recording of this problem. Watch the cursor and the left "thumbnail" view in okular.
Side notes: 0. Clicking in okular first (after moving out and moving in) does not make any difference; 1. I'm using two-finger scrolling (and never set or tried "edge scrolling"); 2. I never use "native scrolling" ("reversed scrolling"); 3. I'm using xf86-input-mtrack (`xf86-input-mtrack-git` package in AUR) as the touchpad driver (but this doesn't seem to be the reason since the problem is not presented in other applications).
By the way, the problem has been there for at least months (but I don't remember the date when I first observe this problem).
I just did a few more tests, and this seems to be a Qt bug as other Qt applications also have this problem (but I didn't observe them because I seldem use touchpad on them) while gtk applications (e.g. chromium) don't. These bugs may all be about this: https://bugreports.qt.io/browse/QTBUG-40829?jql=text%20~%20%22scroll%20touchpad%22 https://bugreports.qt.io/browse/QTBUG-49294
Thanks for the update. Since you mention it's an upstream Qt issue, I'm closing this Okular-specific bug report.
I have be influenced by this bug too. I am running ubuntu 18.04 and the okular version is 1.4.3 When I try to use touchpad to scroll, okular can work well at most of time but sometimes it randomly jumps several lines (in most cases, it jumps half page). If I am scrolling upwards, it jumps upwards. Or it jumps downwards if I initially scrolling downwards. I find that the old version okular in ubuntu 16.04 is free of this bug. This bug seems to take time to be solved completely. Does anyone know how to avoid its influence currently since it is really annoy. I tried to downgrade my current okular to old version but it seems that I can not do that in ubuntu 18.04 and I have to go with the 1.4.3 version. If anyone knows how to solve it, please tell me. Really appreciated! I have reported it via ubuntu's launchpad website. https://bugs.launchpad.net/ubuntu/+source/okular/+bug/1808053
(In reply to GuHua from comment #3) > I just did a few more tests, and this seems to be a Qt bug as other Qt > applications also have this problem (but I didn't observe them because I > seldem use touchpad on them) while gtk applications (e.g. chromium) don't. > > These bugs may all be about this: > > https://bugreports.qt.io/browse/QTBUG- > 40829?jql=text%20~%20%22scroll%20touchpad%22 > https://bugreports.qt.io/browse/QTBUG-49294 Did you have a chance to solve this problem? Thanks.