Public bug reported:
When using the appletouch driver on a Macbook 3,1, the cursor moves in
noticable horizontal or vertical 'steps'. This is particularly
noticeable when dragging a diagonal line. This can make the trackpad
very difficult to use, as it becomes hard to hone in on small objects,
particularly if the user has opted for a faster cursor. This issue is
also described in a forum thread:
http://ubuntuforums.org/showthread.php?t=813884&page=6
There is a workaround that involves modifying and recompiling
appletouch.c with a couple of changes. This is also detailed in bug
#1034132.
Original:
#define ATP_FUZZ 16
#define ATP_THRESHOLD 5
New:
#define ATP_FUZZ 0
#define ATP_THRESHOLD 2
This makes the trackpad much more usable, though slight stepping is
still noticable. I've found the modification below seems to provide a
small amount of additional smoothness:
Original:
pcum += (xy_sensors[i] - threshold) * i;
psum += (xy_sensors[i] - threshold);
New:
pcum += (xy_sensors[i]) * i;
psum += (xy_sensors[i]);
Regression testing will be necessary on the earlier (pre-geyser 4)
models to rule out the possibility that these changes would just be
trading better behavior for some models at the expense of others; if
that were the case, some conditional logic would be in order.
I expect this bug to hit a larger audience as owners of Macbooks too old
for OS X Mavericks begin to migrate to Linux.
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.12.0-7-generic 3.12.0-7.15
ProcVersionSignature: Ubuntu 3.12.0-7.15-generic 3.12.4
Uname: Linux 3.12.0-7-generic x86_64
ApportVersion: 2.12.7-0ubuntu3
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: ubuntu 2706 F.... pulseaudio
CasperVersion: 1.336ubuntu1
CurrentDesktop: Unity
CurrentDmesg:
[ 31.859199] sky2 0000:03:00.0 eth0: Link is up at 1000 Mbps, full duplex,
flow control both
[ 31.859229] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 299.816181] mce: [Hardware Error]: Machine check events logged
Date: Fri Dec 27 03:05:13 2013
IwConfig:
eth0 no wireless extensions.
lo no wireless extensions.
LiveMediaBuild: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20131226)
MachineType: Apple Inc. MacBook3,1
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi
file=/cdrom/preseed/username.seed boot=casper quiet splash --
RelatedPackageVersions:
linux-restricted-modules-3.12.0-7-generic N/A
linux-backports-modules-3.12.0-7-generic N/A
linux-firmware 1.117
RfKill:
0: hci0: Bluetooth
Soft blocked: no
Hard blocked: no
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/05/08
dmi.bios.vendor: Apple Inc.
dmi.bios.version: MB31.88Z.008E.B02.0803051832
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: Mac-F22788C8
dmi.board.vendor: Apple Inc.
dmi.board.version: PVT
dmi.chassis.asset.tag: Asset Tag#
dmi.chassis.type: 2
dmi.chassis.vendor: Apple Inc.
dmi.chassis.version: Mac-F22788C8
dmi.modalias:
dmi:bvnAppleInc.:bvrMB31.88Z.008E.B02.0803051832:bd03/05/08:svnAppleInc.:pnMacBook3,1:pvr1.0:rvnAppleInc.:rnMac-F22788C8:rvrPVT:cvnAppleInc.:ct2:cvrMac-F22788C8:
dmi.product.name: MacBook3,1
dmi.product.version: 1.0
dmi.sys.vendor: Apple Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Confirmed
** Tags: amd64 apport-bug precise quantal raring saucy trusty
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https://bugs.launchpad.net/bugs/1264426
Title:
Appletouch driver moves cursor in steps
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