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<b><a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - Two-finger scrolling jumpy with Synaptics touchpad"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91135#c21">Comment # 21</a>
on <a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - Two-finger scrolling jumpy with Synaptics touchpad"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91135">bug 91135</a>
from <span class="vcard"><a class="email" href="mailto:peter.hutterer@who-t.net" title="Peter Hutterer <peter.hutterer@who-t.net>"> <span class="fn">Peter Hutterer</span></a>
</span></b>
<pre>oh, ffs, I hate these touchpads.
event at 0.968621 has a 6.23mm jump in the x axis
event at 2.340838 has a 8.68mm jump in the x axis
Those two account for the horizontal scroll jump you can see in this recording.
event at 2.487409 has a 8.34mm jump in the y axis
That's the vertical jump close to the end of the recording.
This is in the single-touch emulation, we already disabled true multi-finger
tracking for the semi-mt touchpads because it's unreliable.
it's a bit unclear why this is happening too. The events leading up to this:
2.292016: ↖↑ 3215/2774 | ↖↑ 3696/1269 |
2.316154: ↖↑ 3215/2728 | ↖↑ 3626/1269 |
2.340838: ↖↑ 3215/2721 | ↖← 3218/1269 |
2.365007: ↖↑ 3215/2715 | |
2.389629: ↖← 3215/2713 | |
2.415441: ↖← 3215/2711 | |
2.464192: ↖← 3215/2709 | |
2.487409: ↖↑ 3215/2678 | ↓↘ 3219/1778 |
2.512015: ↑↗ 3216/2658 | ↓↘ 3220/1778 |
2.536274: ↑↗ 3220/2658 | ↓↘ 3221/1778 |
which is a bit confusing because the way I read the kernel's
synaptics_report_semi_mt_data() slot 1 should be the bottom-right touchpoint
but that isn't the case here. but either way, the jump is visible in slot 1
and the single touch emulation tracks slot 1 for coordinates:
2.292016: *********** | ↖← 3696/1269 |
2.316154: *********** | ↙← 3626/1270 |
2.340838: *********** | ↙← 3218/1270 |
2.365007: *********** | |
2.389629: *********** | ↖← 3216/1269 |
2.415441: *********** | |
2.464192: *********** | |
2.487409: *********** | ↓↘ 3222/1778 |
2.512015: *********** | |
2.536274: *********** | →↗ 3224/1777 |
so in short: we don't have a warning about this, it's not caused by a finger
change and all we get is a sudden jump to some other position. which means we
have to find some other heuristics to detect those.</pre>
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