libwacom_has_eraser tells us if this non-eraser tool has an
associated eraser (same serial, different tool id)
libwacom_is_eraser tells us if the current tool is an eraser device.
Now that we always have the stylus for the tool in proximity (see the
previous commit), switch this back to the has_eraser function and
rename it in the process so it's more obviously not the seemingly
obvious interpretation.
This reverts commit 9bd0b94527.
Pens with an integrated eraser share the serial number with the
corresponding pen but differ in the tool ID. libwacom provides a
"paired_id" mapping to look up one from the other.
If the user brings the eraser into proximity the very first time the
tool is seen, the eraser's tool ID is stored in the keyfile instead of
the associated stylus id. This leads to otherwise wrong behavior since
erasers share the serial number with the stylus but don't have any
buttons, don't have any erasers themselves, etc.
Fix this by looking up a matching stylus when we see an eraser. This
effectively filters our CcWacomTool to always be the pen, which is an
inadvertent assumption anyway.
The overwhelmingly vast majority of users will never see anything else
than a "Standard" (i.e. pen-shaped) stylus. And there's a mismatch
between e.g. the Pro Pen 3 being labeled as "Standard stylus" when users
spent money on getting a Pro pen.
Let's drop the "Standard" prefix, it adds nothing in this context.
We generally use tool ID 0 if the ID is actually unknown, libwacom however
assigns 0xfffff to such device. Make it sure we find the "Generic Pen"
stylus description in that case.
Wacom's new "Pro Pen 3D" stylus is declared as a new stylus type within
libwacom: WSTYLUS_3D. Now that the Wacom panel supports arbitrary three-
button styli, we can add specific support for this new stylus type to
suppress the warning message that is generated.
https://bugzilla.gnome.org/show_bug.cgi?id=790028
Similar to CcWacomDevice vs GsdWacomDevice, CcWacomTool is meant to
replace the GsdWacomStylus object. There is a substantial difference
between these two objects, CcWacomTool offers constructor methods,
it expects the caller to maintain lifetime otherwise. while
GsdWacomStylus objects creation was rather fixed (GsdWacomDevice
created all possible styli on initialization). This latter model
doesn't help us use all the possibilities wrt wayland configurability.
