tablet: add support for relative dials

Some tablets provide one or more rotary controls (see e.g. the Huion Inspiroy Dial 2) that provide delta information effectively equivalent to a mouse wheel. Expose those in the same way as the strip or ring controls, with the event matching the wl_pointer.axis_v120 approach.

Like a typical mouse wheel we do not expect there to be a source information, so this is left out of the interface.

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This are the two easy parts of !285 factored out, scrolling is a whole different beast.

Implementations:

• mutter!3724
• gtk!7242
• kwin!7348

ACKS:

• KDE (@zzag)
• GNOME (@jadahl)
• wlroots (@bl4ckb0ne)

Review:

• @jadahl

mentioned in merge request !285

added 12 commits

• 78662cab...e3c6a17a - 9 commits from branch wayland:main
• a78e82f2 - tablet: bump the tablet protocol version
• 34f50cfb - tablet: add a bustype event to the initial burst of tablet events
• 7865890c - tablet: add support for relative dials

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added 2 commits

• 73e8bfec - tablet: add a bustype event to the initial burst of tablet events
• a4767aa1 - tablet: add support for relative dials

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marked this merge request as ready

changed the description

added Needs acks Needs implementations Needs review labels

added 2 commits

• c496cd0f - tablet: add a bustype event to the initial burst of tablet events
• c1814899 - tablet: add support for relative dials

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added 1 commit

• 6154479a - tablet: add support for relative dials

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resolved all threads

ftr, both mutter and gtk now have a positive review so at least those two would be good to go.

Note that I'm adding preliminary support for this in KWin with https://invent.kde.org/plasma/kwin/-/merge_requests/3512, I haven't added support for this addition to the protocol yet but it would be trivial.

added 49 commits

• 6154479a...122a47a1 - 46 commits from branch wayland:main
• 9243d58b - tablet: bump the tablet protocol version
• e4d5414a - tablet: add a bustype event to the initial burst of tablet events
• 14bc4a73 - tablet: add support for relative dials

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Partial KWin implementation (only the bus type): https://invent.kde.org/plasma/kwin/-/merge_requests/6950

I also typed up a trivial Qt implementation, but it doesn't actually do anything with the information, so I'm not sure it counts

Full KWin implementation: https://invent.kde.org/plasma/kwin/-/merge_requests/7348