ubuntu-x-swat team mailing list archive

[Chase Douglas <chase.douglas@xxxxxxxxxxxxx>]

** Description changed:

- Binary package hint: xserver-xorg-input-evdev
+ SRU Justification:
+ ==================
+ In previous releases of xserver-xorg-input-evdev there was an option to invert and/or swap axes. This allowed for simple screen rotation support. In the latest version of the module in Ubuntu, this option has been deprecated in favor of the server-side input coordinate transformation matrix support. See https://wiki.ubuntu.com/X/InputCoordinateTransformation for details. Unfortunately, the XInput 2.1 changes caused the input coordinate transformation matrix support to cause erratic pointer behavior. Without a fix, users cannot reliably use a rotated touchscreen.
+ 
+ The fix involves maintaining and using the proper previous states of the
+ X and Y event coordinates when performing the input coordinate
+ transformation. If one coordinate is updated but not the other, the
+ other's previous untransformed coordinate must be used to compute the
+ correct new transformed coordinates. Then, the new transformed
+ coordinates must be compared to the previous transformed coordinates to
+ see if they should be reported to the client. Unchanged values are not
+ reported in some XI 1.x and 2.x events. The current X server conflates
+ the previous untransformed and previous transformed values and ends up
+ calculating the new transformed values incorrectly.
+ 
+ To reproduce, use xinput to set a new coordinate transformation matrix
+ with a rotation. For example, use a 90 degree turn by setting the input
+ coordinate transformation matrix to 0 -1 1 1 0 0 0 0 1. See the above
+ wiki page for details on how to set the matrix. Then, try to touch the
+ touchscreen and move the cursor. The cursor will jump arround
+ erratically when moving in pure horizontal or pure vertical motions.
+ 
+ The risk of regression is minimal because the only time the fix will
+ cause a change is when the transformation matrix has been modified from
+ the identity matrix to a matrix including some amount of rotation. The
+ patch was also tested in the xorg-edgers ppa for a few weeks before it
+ was even uploaded to Oneiric.
+ 
+ Original Bug Report:
+ ====================
  
  When using something like `xinput set-float-prop $INPUTDEV "Coordinate
  Transformation Matrix" 0.0 -1.0 1.0 1.0 0.0 0.0 0.0 0.0 1.0` to match
  the coordinates of a touchscreen/tablet to a rotated (transformed)
  screen, the cursor moves around erratically.
  
  From the original report of david-dklevine (https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-evdev/+bug/742567/comments/32):
  when a horizontal or vertical drag is performed the cursor jumps wildly - it appears to jump between what it should be according to the coordinate transformation and what it would be if x=0 and y=1 (that is if the second line of the matrix was the identity). With a diagonal drag or a touch the cursor appears where it should be.
  
  In addition to the Cando Multi Touch Panel reported at
  https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-
  evdev/+bug/742567/comments/32, it also affects me with a AsusTek, Inc.
  MultiTouch(TTI) (on Asus EeePC T101MT)
  
  lsb_release -rd
  Description:	Ubuntu 11.04
  Release:	11.04
  
  $ apt-cache policy xserver-xorg-input-evdev
  xserver-xorg-input-evdev:
-   Installed: 1:2.6.0-1ubuntu12
-   Candidate: 1:2.6.0-1ubuntu12
-   Version table:
-  *** 1:2.6.0-1ubuntu12 0
-         500 http://gd.tuwien.ac.at/opsys/linux/ubuntu/archive/ natty/main amd64 Packages
-         100 /var/lib/dpkg/status
+   Installed: 1:2.6.0-1ubuntu12
+   Candidate: 1:2.6.0-1ubuntu12
+   Version table:
+  *** 1:2.6.0-1ubuntu12 0
+         500 http://gd.tuwien.ac.at/opsys/linux/ubuntu/archive/ natty/main amd64 Packages
+         100 /var/lib/dpkg/status

** Patch added: "503_fix_masked_transformed_valuators.patch"
   https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/774938/+attachment/2131372/+files/503_fix_masked_transformed_valuators.patch

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https://bugs.launchpad.net/bugs/774938

Title:
  Erratic cursor movement when using "Coordinate Transformation Matrix"