Smooth scrolling

Simon Thum simon.thum at
Tue Apr 6 09:59:15 PDT 2010

Hi Max,

I've had a small look at your work. I've often had requests to do this
by users who assumed this would work the same way as pointer
acceleration, which unfortunately it doesn't. So I have a small comment
and a suggestion.

The comment first; from your rationale: "The new event would specify the
scrolled range in pixels or inch (needs to be decided!)..."

The problem I see is that it's really degrees or cycles on a wheel, or
some distance on more freaky devices (e.g. pad on mouse). Maybe it's
preferable to add some (user-overrideable) axis information which
toolkits may use to ultimately do something sensible.

Now for my suggestion: when things work fine (i.e. not now ;), you may
want to add acceleration to the scroll wheel. The ptrveloc.h header
contains the necessary methods to create an 'acceleration context', feed
it with the wheel data and map it over acceleration functions. I think
some windows drivers implement such a feature.

In case you're interested, just mail me.



Am 02.04.2010 20:12, schrieb Max Schwarz:
> Am Freitag 02 April 2010 19:46:55 schrieb Dima Ryazanov:
>> I would love this feature. I'm running Linux on a MacBook, and smooth
>> scrolling is the one feature I miss from OS X.
> Glad to hear someone else noticed it :-)
> I started a repository on github (
> and imported a few projects that might need to be changed.
> But after becoming more familiar with the architecture I realised
> the fix actually might be quite small. I've already modified xorg-input-evdev 
> to send exact relative wheel motions again, and report the resolution back to 
> No change to itself was required.
> The applications can identify the right valuator via XI2 and get the 
> resolution info.
> So what's missing is support in frameworks like GTK/Qt, and the change of the 
> synaptics input driver. The frameworks just need to detect the new valuator 
> via XI2, and listen to the valuator events instead of the old button presses 
> (which will still be sent out).
> As I'm just finishing another project of mine, I won't have time for pscroll 
> in the next two weeks, but after that at least a patch for firefox should be 
> ready, as that is the most annoying occurance of clicky-scrolling for me. 
> (firefox uses it's own scrolling system, not GTK's)
> Max
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