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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - wl_fixed is not precise enough for high dpi mice"
href="https://bugs.freedesktop.org/show_bug.cgi?id=85715">85715</a>
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<th>Summary</th>
<td>wl_fixed is not precise enough for high dpi mice
</td>
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<th>Product</th>
<td>Wayland
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
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<th>Component</th>
<td>weston
</td>
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<th>Assignee</th>
<td>wayland-bugs@lists.freedesktop.org
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<th>Reporter</th>
<td>derekf@osg.samsung.com
</td>
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<p>
<div>
<pre>(Related to <a class="bz_bug_link
bz_status_NEW "
title="NEW - Improve pointer acceleration for high-resolution mice"
href="show_bug.cgi?id=85632">bug 85632</a>)
I have a mouse here (a Razer Abyssus) with a 3500DPI sensor.
There is discussion about having libinput normalize mouse input to a 400dpi
standard - some patches have landed in libinput, but there isn't yet a way to
change from the default 400dpi setting.
Once that works, this 3500 dpi mouse will have its deltas multiplied by
400/3500 before being fed to the pointer acceleration filter. On the other end
of the accel filter this slow motion becomes even slower, and the deltas end up
below the threshold for wl_fixed. It's entirely possible to slowly move your
mouse along indefinitely without any motion occurring.
I have confirmed that this is not just really slow motion (that will eventually
accumulate to on screen movement) - motion is being rounded to zero during the
wl_fixed_to_double() conversion in weston's libinput-device.c
To reproduce:
Get a ridiculous mouse. The more blue LEDs the better. (3000+ DPI can show the
problem easily, 2000 will do in a pinch)
Use libinput master branch and change device->dpi = DEFAULT_MOUSE_DPI; in
src/evdev.c to whatever is appropriate</pre>
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