source/blender/windowmanager/WM_types.h

@@ -639,6 +639,8 @@ typedef struct wmTabletData {
   float x_tilt;
   /** as above. */
   float y_tilt;
+  /** range (-pi,pi), with stylus button to the left side being 0. */
+  float twist;
   /** Interpret mouse motion as absolute as typical for tablets. */
   char is_motion_absolute;
 } wmTabletData;

source/blender/windowmanager/intern/wm_event_system.cc

@@ -5138,6 +5138,7 @@ void wm_tablet_data_from_ghost(const GHOST_TabletData *tablet_data, wmTabletData
     wmtab->pressure = wm_pressure_curve(tablet_data->Pressure);
     wmtab->x_tilt = tablet_data->Xtilt;
     wmtab->y_tilt = tablet_data->Ytilt;
+    wmtab->twist = tablet_data->Twist;
     /* We could have a preference to support relative tablet motion (we can't detect that). */
     wmtab->is_motion_absolute = true;
     // printf("%s: using tablet %.5f\n", __func__, wmtab->pressure);