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Peter Hutterer authored
Touchpads are limited by a fixed sampling rate (usually 80Hz). Some finger changes may happen too fast for this sampling rate, resulting in two distinct event sequences: * finger 1 up and finger 2 down in the same EV_SYN frame. Synaptics sees one finger down before and after and the changed coordinates * finger 1 up and finger 2 down _between_ two EV_SYN frames. Synaptics sees one touchpoint move from f1 position to f2 position. That move causes a large cursor jump. The former could be solved (with difficulty) by adding fake EV_SYN handling after releasing touchpoints but that won't fix the latter case. So as a solution for now limit the finger movement to 20mm per event. Tests on a T440 and an x220 showed that this is just above what a reasonable finger movement would trigger. If a movement is greater than that limit, reset it to 0/0. On devices without resolution, use 0.25 of the touchpad's diagonal instead. Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
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