macOS: follow system preference for natural trackpad scroll direction

And remove Blender preference, which was expected to be set to match the system
preference for correct behavior. Instead just handle this automatically.

Differential Revision: https://developer.blender.org/D9402

4 files changed, 42 insertions, 0 deletions

diff --git a/source/blender/windowmanager/WM_api.h b/source/blender/windowmanager/WM_api.h
index b81ef14f21c..fd0b99fb9ae 100644
--- a/source/blender/windowmanager/WM_api.h
+++ b/source/blender/windowmanager/WM_api.h
@@ -857,6 +857,9 @@ void WM_event_ndof_to_quat(const struct wmNDOFMotionData *ndof, float q[4]);
 float WM_event_tablet_data(const struct wmEvent *event, int *pen_flip, float tilt[2]);
 bool WM_event_is_tablet(const struct wmEvent *event);
 
+int WM_event_absolute_delta_x(const struct wmEvent *event);
+int WM_event_absolute_delta_y(const struct wmEvent *event);
+
 #ifdef WITH_INPUT_IME
 bool WM_event_is_ime_switch(const struct wmEvent *event);
 #endif
diff --git a/source/blender/windowmanager/WM_types.h b/source/blender/windowmanager/WM_types.h
index a8d24205268..7fa2851cbf3 100644
--- a/source/blender/windowmanager/WM_types.h
+++ b/source/blender/windowmanager/WM_types.h
@@ -595,6 +595,10 @@ typedef struct wmEvent {
   /** Ascii, unicode, mouse coords, angles, vectors, dragdrop info. */
   void *customdata;
 
+  /* True if the operating system inverted the delta x/y values and resulting
+   * prev x/y values, for natural scroll direction. For absolute scroll direction,
+   * the delta must be negated again. */
+  char is_direction_inverted;
 } wmEvent;
 
 /**
diff --git a/source/blender/windowmanager/intern/wm_event_query.c b/source/blender/windowmanager/intern/wm_event_query.c
index db80296bdb8..a996796104b 100644
--- a/source/blender/windowmanager/intern/wm_event_query.c
+++ b/source/blender/windowmanager/intern/wm_event_query.c
@@ -423,6 +423,38 @@ bool WM_event_is_tablet(const struct wmEvent *event)
 /** \} */
 
 /* -------------------------------------------------------------------- */
+/** \name Event Scroll's Absolute Deltas
+ *
+ * User may change the scroll behavior, and the deltas are automatically inverted.
+ * These functions return the absolute direction, swipe up/right gives positive values.
+ *
+ * \{ */
+
+int WM_event_absolute_delta_x(const struct wmEvent *event)
+{
+  int dx = event->x - event->prevx;
+
+  if (!event->is_direction_inverted) {
+    dx = -dx;
+  }
+
+  return dx;
+}
+
+int WM_event_absolute_delta_y(const struct wmEvent *event)
+{
+  int dy = event->y - event->prevy;
+
+  if (!event->is_direction_inverted) {
+    dy = -dy;
+  }
+
+  return dy;
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
 /** \name Event IME Input Access
  * \{ */
 
diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index 071951abda3..bf970aa2034 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -4397,6 +4397,9 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, void
       event.prevx = event.x - pd->deltaX;
       event.prevy = event.y - (-pd->deltaY);
 
+      /* The direction is inverted from the device due to system preferences. */
+      event.is_direction_inverted = pd->isDirectionInverted;
+
       wm_event_add(win, &event);
       break;
     }