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Evdev is a 100% stateful protocol. The following represents three touches. Two touches begin and end at the same time at (500, 500) and (1000, 1000). The third touch begins after the first two end, and is at (500, 500). ABS_MT_SLOT 0 /* Set touch slot */ ABS_MT_TRACKING_ID 0 /* New touch with ID 0 in slot 0 */ ABS_MT_POSITION_X 500 /* Initial X position */ ABS_MT_POSITION_Y 500 /* Initial Y position */ ABS_MT_SLOT 1 /* Set touch slot */ ABS_MT_TRACKING_ID 1 /* New touch with ID 1 in slot 1 */ ABS_MT_POSITION_X 1000 /* Initial X position */ ABS_MT_POSITION_Y 1000 /* Initial Y position */ SYNC /* End of frame */ ABS_MT_SLOT 0 /* Go back to slot 0 */ ABS_MT_TRACKING_ID -1 /* Touch in slot 0 ended */ ABS_MT_SLOT 1 /* Go to slot 1 */ ABS_MT_TRACKING_ID -1 /* Touch in slot 1 ended */ SYNC /* End of frame */ ABS_MT_SLOT 0 /* Go back to slot 0 */ ABS_MT_TRACKING_ID 2 /* New touch in slot 0 with ID 2 */ SYNC /* End of frame */ ABS_MT_TRACKING_ID -1 /* Touch in last slot (0) ended */ SYNC /* End of frame */ Note that touch 2 has the same X and Y position as touch 0. This is implied because no new value was emitted for slot 0. In fact, Linux will not emit an event in the same slot with the same event type and code unless the value has changed. Thus, we can only assume that all the MT valuators have the same values as they were when they were last sent for the given slot. This change adds an array of valuator mask to hold all the last valuator values that came from evdev for each slot. When a new touch begins, all the last values are copied into it. This patch assumes initial axis values of 0 in each slot. Linux and mtdev do not provide a facility to query the current values of axes in each slot yet. This may cause spurious incorrect touch valuator values at the beginning of an X session, but there's nothing we can do about it right now. Signed-off-by: Chase Douglas <chase.douglas@canonical.com> Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
xf86-input-evdev - Generic Linux input driver for the Xorg X server
Please submit bugs & patches to the Xorg bugzilla:
https://bugs.freedesktop.org/enter_bug.cgi?product=xorg
All questions regarding this software should be directed at the
Xorg mailing list:
http://lists.freedesktop.org/mailman/listinfo/xorg
The master development code repository can be found at:
git://anongit.freedesktop.org/git/xorg/driver/xf86-input-evdev
http://cgit.freedesktop.org/xorg/driver/xf86-input-evdev
For more information on the git code manager, see:
http://wiki.x.org/wiki/GitPage