Bug 420842

Summary: Scrolling with browse tool sticks at first after inertial scrolling implemented
Product: [Applications] okular Reporter: Michael D <nortexoid>
Component: generalAssignee: Okular developers <okular-devel>
Severity: minor CC: aacid, jsardid, keziolio123, nate, oliver.sander
Priority: NOR Keywords: regression
Version: 1.9.80   
Target Milestone: ---   
Platform: Manjaro   
OS: Linux   
Latest Commit: Version Fixed In: 1.11.2

Description Michael D 2020-05-01 08:16:07 UTC
Inertial scrolling was just implmented in okular, which is awesome. However, scrolling with the browse (hand) tool (by left-clicking the document and pulling it down or up) now sticks for a good number of pixels before it starts moving, which causes it to jump for the first part of the scroll and is jarring for the user.
Comment 1 Michael D 2020-05-01 08:17:10 UTC
This is most noticeable, by the way, the more slowly you drag scroll the document.
Comment 2 David Hurka 2020-05-01 10:22:43 UTC
I recognized that when I was playing arround with my new trackpoint, but couldn’t verify the link to smooth scrolling. 

I assume you recently updated Okular, and recognized that you got smooth scrolling and this bug the same time.

When smooth scrolling will be reimplemented, we should test this.
Comment 3 Michael D 2020-05-01 10:40:24 UTC
Yes, I recently updated okular knowing that smooth scrolling was implemented and noticed immediately after the sticky drag scroll, since I view a lot of pdfs daily and my preferred scroll method is using the browse tool (since it's smoother than using the mouse wheel).
Comment 4 Keziolio 2020-05-03 21:02:46 UTC
This is a QScroller feature almost for sure.

It's one of the configuration parameters that Qt documentation explicitly says to keep to the "platform optimized" values.


You feel it's too severe?

(btw, try it in your phone, it does the same)
Comment 5 Michael D 2020-05-03 21:27:51 UTC
It's not noticeable on Android because the scroll doesn't jump. It feels too severe to me and doesn't even exist using touch input in okular, as far as I can tell.
Comment 6 Nate Graham 2020-05-04 21:46:47 UTC
Can confirm. There seems to be a small initial threshold before the grab actually moves the document, at which point it jumps. Either the threshold or the jump should be removed.
Comment 7 Bug Janitor Service 2020-09-15 12:13:51 UTC
A possibly relevant merge request was started @ https://invent.kde.org/graphics/okular/-/merge_requests/272
Comment 8 Oliver Sander 2020-09-15 15:50:33 UTC
Git commit a5be0149ec627fbc086e5b26cbbe7be13cde49b8 by Oliver Sander, on behalf of Kezi Olio.
Committed on 15/09/2020 at 12:11.
Pushed by ngraham into branch 'release/20.08'.

Restore mouse drag scrolling, so it starts immediately

QScroller uses a minimum drag distance before drag scrolling starts by default.
This sets the minimum distance to 0.0, to restore the original behavior of the Browse tool.

M  +1    -0    ui/pageview.cpp

Comment 9 Michael D 2020-09-15 15:54:29 UTC
Thanks for the fix!