[Vm-dev] Disagreement on sign of mouse wheels

Tom Beckmann tomjonabc at gmail.com
Tue Dec 31 07:26:29 UTC 2019

Hi Nicolas,

on my ubuntu, running with the synaptics touchpad driver and "natural
scrolling" enabled, I get the same default behavior as you describe. You
can double check that this is the expected behavior by finding a page in
your browser that overflows horizontally and checking whether it also moves
right as your fingers move right. I typically mod the horizontal axis via
`xinput set-prop` to get consistent behavior on both axes. The libinput
driver (an alternative to synaptics that is used by default on wayland to
my knowledge) appears to send negative to the bottom-right on both axes by
So, if your browser on linux behaves the same, you should likely just keep
the signs unchanged and leave it to the user to make this behavior
consistent/adapt it to their liking, as it is an OS preference.

What you might also be interested in, I started integrating xinput2 into
the OSVM:
This enables "pixel perfect" scrolling events and multitouch on linux. In
the branch I took the liberty to define a new event type for touch events
(ignoring the existing work for iOS that appeared to opt for a generic
complex event type). It is still a work-in-progress, as xinput2 requires
handling devicechanged events on the application side and some other things
like modifier masks changed, which I haven't taken the time to look into
yet. And of course, the design for touch events would need to be discussed
to get the most future proof and cross-platform-compatible version.


On Mon, Dec 30, 2019 at 9:26 PM Nicolas Cellier <
nicolas.cellier.aka.nice at gmail.com> wrote:

> Hi all,
> there is still an issue with horizontal mouse wheels with latest VM, and
> (Smalltalk sendMouseWheelEvents: true)
> When I sweep the trackpad from bottom to top (with two fingers on
> MacBook), I get  negative yDelta on the 3 OS, OSX, linux, Windows, all good.
> When I sweep the trackpad from right to left (with two finders on Mac) , I
> get:
> - negative xDelta on OSX
> - positive xDelta on linux and Windows
> I don't know whether it's due to Parallels VM, or same on native
> windows/linux... Could someone confirm?
> If so, I don't know which sign to change, what would you expect?
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