Mouse speed questions: GNOME, Xorg, oh my...

Adam Williamson awilliam at
Thu May 2 19:26:54 UTC 2013

On Thu, 2013-05-02 at 11:34 -0700, Adam Williamson wrote:

> How is this ConstantDeceleration default set? It doesn't seem to be a
> universal value; the mouse on my desktop, for instance, has it set to
> 1.0. So is it set by the driver? By the server? Is it dependent on the
> ID of the device? (which would seem problematic, as the same touchpad
> will behave 'differently' with different resolution displays, one
> assumes). The ID of the system it's in? What?

With a bit of research, it looks like Constant Deceleration 2.5 is just
a universal default for synaptics; my old laptop has the same value, and

synaptics "Constant Deceleration" 2.5

produces a bunch of hits (other values don't). I think actually the
synaptics driver defaults its 'MinSpeed' value to 2.5, and then
translates that to "Constant Deceleration" of 2.5 (this is what the X
log indicates).

I'm suspecting the fact that Dell produced the XPS 13 with a 1366x768
display, then revved it with a 1920x1080 display but without changing
anything else, may have something to do with this. Possibly they tweaked
the touchpad with the initial hardware rev, then didn't change its
settings when bumping the display resolution. 

1920/1366 = 1.406
2.5/1.6 = 1.56

reasonably close...

A few posters in an Ubuntu forum thread - - complain
about the same issue.
Adam Williamson
Fedora QA Community Monkey
IRC: adamw | Twitter: AdamW_Fedora | adamwfedora

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