[okular] [Bug 420492] 20.04.0 significantly slows down mouse scrolling with a "hyperscroll" mouse or a touchpad driver that sends mouse wheel scroll events when configured for greater speed

[roger truong]

https://bugs.kde.org/show_bug.cgi?id=420492

--- Comment #13 from roger truong <dragonrmartin at gmail.com> ---
After looking through the rest of pageview.cpp, I think I narrowed down the
problem to the auto limit_value function. 

https://invent.kde.org/kde/okular/-/blob/master/ui/pageview.cpp#L5369
https://invent.kde.org/kde/okular/-/blob/master/ui/pageview.cpp#L5400


(In reply to Keziolio from comment #10)
> Regarding the original bug, the behaviour of the scroll events is programmed
> to be literally the same as it was before, probably QScroller::scrollTo
> behaves in a suboptimal way if it's flooded with events, I'll see if
> something comes to mind

Changing the value for nSteps to 2000 from 200 brought back the scrolling from
previous versions. It seems that the regression may be in animation speed
rather than scrolling if none of the code has changed.

It also brought up another bug in the animations with the Contents view. When
continuously scrolling, the headings don't advance as they did in 1.9.x. It
jumps to whatever heading the current page is on once scrolling has stopped.
I'm unsure if this qualifies for a separate bug report, as the synchronous
nature of the animations lead me to believe these bugs may be related. The
effect can be seen in Contents pane of the videos attached in the OP as well.

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