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<base href="https://bugs.freedesktop.org/" />
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<th>Priority</th>
<td>medium
</td>
</tr>
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Touch points get out of sync with single touch devices; clients stop receiving events"
href="https://bugs.freedesktop.org/show_bug.cgi?id=69759">69759</a>
</td>
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<th>Assignee</th>
<td>wayland-bugs@lists.freedesktop.org
</td>
</tr>
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<th>Summary</th>
<td>Touch points get out of sync with single touch devices; clients stop receiving events
</td>
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<th>Severity</th>
<td>critical
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Reporter</th>
<td>ullysses.a.eoff@intel.com
</td>
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<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Component</th>
<td>weston
</td>
</tr>
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<th>Product</th>
<td>Wayland
</td>
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<pre>In corollary to <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Touch events dropped after multiple touchpoints hit at once"
href="show_bug.cgi?id=67563">Bug 67563</a>, I can trigger weston to stop processing touch events
with a single touch device. It's hard to trigger, but by rapidly tapping the
screen in random places, Weston eventually gets into a state where it stops
sending touch events to the clients.
After a little debugging, I found that input.c::notify_touch() gets invoked
with a value of WL_TOUCH_UP by evdev.c::evdev_process_key() twice in a row when
seat->num_tp==1 prior to the first WL_TOUCH_UP. This results in seat->num_tp
getting decremented too many times, hence halting client touch notifications.
In other words, the number of invocations of notify_touch(WL_TOUCH_DOWN) and
notify_touch(WL_TOUCH_UP) are not symmetric. Beyond this, I'm not sure what
triggers evdev_process_key() to handle two BTN_TOUCH 0 events in a row... since
evtest BTN_TOUCH 1 and BTN_TOUCH 0 events appear to be symmetric.
evtest logs are forthcoming.</pre>
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