When enabling a second screen, say horizontally next to the primary screen, horizontal touchpad speed increases proportionally to the increase in horizontal resolution. I assume the same happens when enabling multiple screens in a vertical configuration. So, it seems that touchpad speed is relative to the total screen layout size in each axis. This is quite irritating. It would be more reasonable to define speed in absolute terms (pixels/sec) rather than relative terms (% x/y resolution / sec), thereby keeping speed in both axes constant, regardless of the addition/removal of extra screens.
I've noticed this on my Thinkpad W510 running Maverick amd64, the latest nvidia binary blob, utouch 1.1, synaptics-dkms 1.0.0, and xserver-xorg-input-synaptics 1.2.2-2ubuntu5
Note that external mice don't exhibit this problem. This might be why this situation isn't encountered often: when plugged into an external monitor, the user is more likely to also plug in an external mouse rather than rely on the touchpad.
This was brought up by Ricardo Caldeira at https://bugs.launchpad.net/xorg-driver-synaptics/+bug/308191/comments/187, and Duncan McGreggor replied at https://bugs.launchpad.net/xorg-driver-synaptics/+bug/308191/comments/189.
Created attachment 40284
Xorg.0.log
I've installed Ubuntu 10.10 on two netbooks, one Acer D250 and one Samsung nf310.
Both have a problem with the synaptics driver. The horizontal acceleration is greater than the vertical, hence the pointer is not very precise and it's very annoying.
This can be solved by tweaking the config:
On the samsung I use:
Option "VertResolution" "135"
Option "HorizResolution" "100"
And on the Acer:
Option "VertResolution" "1"
Option "HorizResolution" "1"
But the driver should be able to auto identify this, especially since windows gets it right.
The driver seems to have problems loading as there is stuff like this in the Xorg.0.log on both machines:
[ 495.943] (EE) Query no Synaptics: 6003C8
[ 495.943] (--) SynPS/2 Synaptics TouchPad: no supported touchpad found
[ 495.943] (EE) SynPS/2 Synaptics TouchPad Unable to query/initialize Synaptics hardware.
[ 495.944] (EE) PreInit returned NULL for "SynPS/2 Synaptics TouchPad"
But the touchpad works anyway and it's possible to use touchpad features like tapping and scrolling.
The Xserver is version 1.9.0 and synaptics is version 1.3.99 from git but 1.2.2 that came with ubuntu had this problem too. I've attatched the Xorg.0.log from the samsung (the one from the acer is similar). The log is taken when my tweaks are disabled.