Cleanup/refactor: Undosys: Get rid of the magic values for undo direction.

Move `eUndoStepDir` to `BKE_undo_system.h` and use its values
everywhere.

Note that this also introduce the `STEP_INVALID` value in that enum.

Finally, kept the matching struct members in some lower-level readfile
code as an `int` to avoid having to include `BKE_undo_system.h` in a lot
of unrelated files.

1 files changed, 5 insertions, 2 deletions

diff --git a/source/blender/editors/curve/editcurve_undo.c b/source/blender/editors/curve/editcurve_undo.c
index 534d29c0cc7..681f387e83e 100644
--- a/source/blender/editors/curve/editcurve_undo.c
+++ b/source/blender/editors/curve/editcurve_undo.c
@@ -238,8 +238,11 @@ static bool curve_undosys_step_encode(struct bContext *C, struct Main *bmain, Un
   return true;
 }
 
-static void curve_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int UNUSED(dir), bool UNUSED(is_final))
+static void curve_undosys_step_decode(struct bContext *C,
+                                      struct Main *bmain,
+                                      UndoStep *us_p,
+                                      const eUndoStepDir UNUSED(dir),
+                                      bool UNUSED(is_final))
 {
   CurveUndoStep *us = (CurveUndoStep *)us_p;