2026-04-18


Observations about how a Wacom Art Pen behaves by default in various painting applications.

Wacom's native driver:

Photoshop:
- twist clockwise, cursor rotates clockwise
- cursor doesn't update while painting, but twist continues to honor correct direction
- no apparent preference for direction inversion

Illustrator:
- twist clockwise, cursor remains stationary
- cursor doesn't update while painting, but twist continues to honor correct direction
- no apparent preference for direction inversion

Krita:
- twist clockwise, cursor rotates clockwise
- cursor updates while painting, with twist honoring correct direction
- no apparent preference for direction inversion

Rebelle:
- twist clockwise, cursor rotates counter-clockwise
- cursor updates while painting, with twist honoring reverse correct direction 
- correctable globally in app preferences


Mocktab custom driver (2026-04-18):


Photoshop:
- no rotation without driver's tilt-to-rotation hack
- twist clockwise, cursor rotates counter-clockwise
- hack enabled: cursor stationary while painting, with twist honoring reverse correct direction 

Krita:
- twist clockwise, cursor rotates counter-clockwise
- cursor updates while painting, with twist honoring reversed rotation direction


Rebelle:
- twist clockwise, cursor rotates counter-clockwise
- cursor updates while painting, with twist honoring reverse rotation direction 


Illustrator:
- twist clockwise, cursor remains stationary
- cursor doesn't update while painting, but twist honors reverse direction


Overall:
- Mocktab's Info pane features a rotation visualizer that rotates in the reverse direction as the pen's physical motion; probably OK if it represents the ground truth about what the driver is actually doing
- Using Mocktab's built-in toggles, all of these apps operate correctly
- UI theory: A good user interface requires no configuration at all.  If users have to change a setting, that means the interface design or its defaults are inadequate.


Fix (2026-04-18):

Root cause identified: the reversed behavior in all apps was caused by a decoder formula error,
not app-specific conventions. The formula `(rawRot + 900) / 5` produced the wrong direction for
macOS's kCGTabletEventRotation convention. Development had been calibrated against a Rebelle
instance with its built-in inversion already enabled, masking the bug.

Fix applied in IntuosV2Decoder (USB + BT paths): negated the formula so clockwise twist produces
clockwise output. The invertRotation toggle remains as an edge-case opt-out.

After fix: all apps work correctly with zero configuration. The Info pane visualizer now also
rotates clockwise on clockwise twist.