** Changed in: linux (Ubuntu) Assignee: (unassigned) => Clinton (cssprain)
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1264426 Title: Appletouch driver moves cursor in steps Status in “linux” package in Ubuntu: Confirmed Bug description: When using the appletouch driver on a Macbook 3,1, the cursor moves in noticeable 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 noticeable. 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]); Another change that seems to help is using more than one previous cursor sample when averaging out the movement towards the desired new cursor position: Original: x = (dev->x_old * 3 + x) >> 2; y = (dev->y_old * 3 + y) >> 2; New: x = (dev->x_older + dev->x_old * 2 + x) >> 2; y = (dev->y_older + dev->y_old * 2 + y) >> 2; Put together, these changes make the stepping as close to imperceptible as can be reasonably expected given the hardware. 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1264426/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp