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Date:   Sat, 4 Nov 2023 07:46:48 +0700
From:   Bagas Sanjaya <bagasdotme@gmail.com>
To:     Illia Ostapyshyn <ostapyshyn@sra.uni-hannover.de>, jkosina@suse.cz
Cc:     benjamin.tissoires@redhat.com, davidrevoy@protonmail.com,
        jason.gerecke@wacom.com, jose.exposito89@gmail.com,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        nils@nilsfuhler.de, peter.hutterer@who-t.net, ping.cheng@wacom.com
Subject: Re: Requesting your attention and expertise regarding a
 Tablet/Kernel issue
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References: <nycvar.YFH.7.76.2311012033290.29220@cbobk.fhfr.pm>
 <20231103200524.53930-1-ostapyshyn@sra.uni-hannover.de>
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On Fri, Nov 03, 2023 at 09:05:25PM +0100, Illia Ostapyshyn wrote:
> Hello David, Hello Jiri,
>=20
> The XP-Pen hardware reports the Eraser usage for the upper stylus button.
> Generally, styli report Invert usages when erasing, as described in [1].
> XP-Pen digitizers, however, tend to omit them.
>=20
> The generic driver maps the Eraser usage to BTN_TOUCH and the Invert
> usage to BTN_TOOL_RUBBER.  Pens conforming to [1] send the Invert usage
> first (switching the tool to BTN_TOOL_RUBBER) followed by Eraser, which
> appears in userspace as a BTN_TOUCH event with the rubber tool set.
>=20
> Due to an oversight, devices not reporting Invert had the BTN_TOOL_RUBBER
> event masked.  This has caused the kernel to send only BTN_TOUCH events
> without the tool switch when erasing.
>=20
> The situation got worse with refactoring done in 87562fcd1342.  An eraser
> without Invert caused the hidinput_hid_event state machine to get stuck
> with BTN_TOOL_RUBBER internally (due to it being masked).  For the
> userspace, this looked as if the pen was never hovering again, rendering
> it unusable until the next reset.  276e14e6c3 fixes this by adding
> support for digitizers that do not report Invert usages when erasing.
>=20
> ---
>=20
> David, we are sorry that our patch broke your workflow.  However,
> forwarding hardware events *as-is* to the userspace has always been the
> intended behavior, with a kernel bug preventing it so far.  You can still
> remap the eraser button to a right click using xsetwacom:
>=20
> xsetwacom set "UGTABLET 24 inch PenDisplay eraser" "Button" "1" "3"
>=20
> Replace the device name with the corresponding *eraser* device from
> "xsetwacom list devices".  You can also do this with "xinput set-button-m=
ap",
> which works for libinput as well.  We have tested this with several
> XP-Pen devices, including Artist 24.
>=20
> [1] https://learn.microsoft.com/en-us/windows-hardware/design/component-g=
uidelines/windows-pen-states

Thanks for the explanation!

--=20
An old man doll... just what I always wanted! - Clara

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