<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - Wobbly AlpsPS/2 ALPS DualPoint TouchPad" href="https://bugs.freedesktop.org/show_bug.cgi?id=104828#c18">Comment # 18</a> on <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - Wobbly AlpsPS/2 ALPS DualPoint TouchPad" href="https://bugs.freedesktop.org/show_bug.cgi?id=104828">bug 104828</a> from <a class="email" href="mailto:Hi-Angel@yandex.ru" title="Hi-Angel <Hi-Angel@yandex.ru>"> Hi-Angel</a> <pre>(In reply to Peter Hutterer from <a href="show_bug.cgi?id=104828#c17">comment #17</a>) > the algorighm is *really* simple right now - it sets a timer on the last > motion event. If the timer expires without further motion events (and no > finger up) we assume that there isn't any wobble. We don't even look at the > motion events themselves. > > For small wobbles setting the fuzz on the axis would be sufficient (kernel > takes care of that), but that also depends on the distance of the events. I > haven't found the time to analyse this yet, stuck with other things. I've looked at hysteresis algo (i.e. evdev_hysteresis function) — I like how it's being so simple and CPU-nonintensive and yet so efficient. I think it's better to write a separate function specifically to check the presence of wobbling, but I admit the solution is unclear. I just wanted to document some points I found before going to sleep. 1. The wobbling detection in abstract vacuum is indeed easy: after a finger is down for 100ms, record all movement along X axis, then divide sum of movement to the left by sum of movement to the right. If the absolute value less-than-or-equal to 2, it wobbles. 2. This function should only be used when the finger is still, because per my experiments making a straight line with such a touchpad shows no sign of wobbling. Detecting a still finger, given a random touchpad can filter out the wobbling or not, is a question. 3. Before deciding to disable hysteresis (because the function didn't detect wobbling), this function should be run multiple times. Otherwise it's possible that upon running the check there was the frame loss which this bug is all about, thus the function would misdetect like there's no wobbling. And it can happen again and again. Then, how much should the check be ran to be sure hysteresis can be safely disabled.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> </ul> </body> </html>