Synaptics Palm Detection patch

debug_palm.diff

diff -aur xf86-input-synaptics-1.8.0/src/synaptics.c xf86-input-synaptics-1.8.0.new/src/synaptics.c
--- xf86-input-synaptics-1.8.0/src/synaptics.c	2014-05-12 21:17:46.000000000 -0400
+++ xf86-input-synaptics-1.8.0.new/src/synaptics.c	2014-05-30 14:49:39.123104990 -0400
@@ -1793,28 +1793,19 @@
 
     /* palm detection */
 
-    if ((hw->z > para->palm_min_z) && (hw->fingerWidth > para->palm_min_width))
+    if ((hw->z > para->palm_min_z))
         return FS_BLOCKED;
 
-    if (hw->x == 0 || priv->finger_state == FS_UNTOUCHED)
-        priv->avg_width = 0;
-    else
-        priv->avg_width += (hw->fingerWidth - priv->avg_width + 1) / 2;
-
     if (finger != FS_UNTOUCHED && priv->finger_state == FS_UNTOUCHED) {
-        int safe_width = MAX(hw->fingerWidth, priv->avg_width);
-
         if (hw->numFingers > 1 ||       /* more than one finger -> not a palm */
-            ((safe_width < 6) && (priv->prev_z < para->finger_high)) || /* thin finger, distinct touch -> not a palm */
-            ((safe_width < 7) && (priv->prev_z < para->finger_high / 2))) {     /* thin finger, distinct touch -> not a palm */
+            (priv->prev_z < para->finger_high) || /* thin finger, distinct touch -> not a palm */
+            (priv->prev_z < para->finger_high / 2)) {     /* thin finger, distinct touch -> not a palm */
             /* leave finger value as is */
         }
         else if (hw->z > priv->prev_z + 1)      /* z not stable, may be a palm */
             finger = FS_UNTOUCHED;
         else if (hw->z < priv->prev_z - 5)      /* z not stable, may be a palm */
             finger = FS_UNTOUCHED;
-        else if (hw->fingerWidth > para->palm_min_width)        /* finger width too large -> probably palm */
-            finger = FS_UNTOUCHED;
     }
     priv->prev_z = hw->z;
 

PKGBUILD

# $Id: PKGBUILD 213056 2014-05-18 13:44:18Z andyrtr $
# Maintainer: Jan de Groot <[email protected]>
# Contributor: Tobias Powalowski  <[email protected]>
# Contributor: Thomas Bächler <[email protected]>
# Contributor: Alexander Baldeck <[email protected]>

pkgname=xf86-input-synaptics
pkgver=1.8.0
pkgrel=2
pkgdesc="Synaptics driver for notebook touchpads"
arch=('i686' 'x86_64')
license=('custom')
url="http://xorg.freedesktop.org/"
depends=('libxtst' 'mtdev' 'libevdev')
makedepends=('xorg-server-devel' 'X-ABI-XINPUT_VERSION=20' 'libxi' 'libx11' 'resourceproto' 'scrnsaverproto')
conflicts=('xorg-server<1.15.0' 'X-ABI-XINPUT_VERSION<20' 'X-ABI-XINPUT_VERSION>=21')
replaces=('synaptics')
provides=('synaptics')
conflicts=('synaptics')
groups=('xorg-drivers' 'xorg')
backup=('etc/X11/xorg.conf.d/50-synaptics.conf')
source=(http://xorg.freedesktop.org/releases/individual/driver/${pkgname}-${pkgver}.tar.bz2
        add_tapbuttons.diff
		debug_palm.diff)
sha256sums=('9bf27632aaa6c5e62621ca9c2ca00f9b309c85b039ee33cd592b189fc872c37a'
            '5298d3e871db3768b34cf8516d3f53f9291202e2ea5de3300256e1cd9119a1ec'
            'bc7ea1967a31c4fe5ebdfec7154eeba88c2fac93915f15e37094e4e20bf5fac7')

build() {
  cd ${pkgname}-${pkgver}
  
  # * upstream disabled tapping by default if a physical left button is present - see FS#33282
  # * enable MatchDevicePath directive by default - FS#33291
  patch -Np1 -i ${srcdir}/add_tapbuttons.diff
  # palm detection debugging
  patch -p1 -i ${srcdir}/debug_palm.diff
  
  ./configure --prefix=/usr
  make
}

package() {
  cd ${pkgname}-${pkgver}
  make DESTDIR="${pkgdir}" install
  install -m755 -d "${pkgdir}/etc/X11/xorg.conf.d"
  install -m644 conf/50-synaptics.conf "${pkgdir}/etc/X11/xorg.conf.d/"
  install -m755 -d "${pkgdir}/usr/share/licenses/${pkgname}"
  install -m644 COPYING "${pkgdir}/usr/share/licenses/${pkgname}/"

  rm -rf "${pkgdir}/usr/share/X11"
}

Thanks for this patch! This issue was driving me nuts and basically made my brand new laptop unusable. You have made it enjoyable to use again!

Question from a noob, how do I apply this patch on Ubuntu? I cannot find how to build the PKGBUILD. Thanks!
(Apologies for commenting on an old thread, but being dissatisfied with libinput, I wanted to give this one a try.)