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, 1 insertions, 1 deletions

diff --git a/source/blender/editors/physics/particle_edit_undo.c b/source/blender/editors/physics/particle_edit_undo.c
index 77b8d410d81..5d2e0e5b6ef 100644
--- a/source/blender/editors/physics/particle_edit_undo.c
+++ b/source/blender/editors/physics/particle_edit_undo.c
@@ -247,7 +247,7 @@ static bool particle_undosys_step_encode(struct bContext *C,
 static void particle_undosys_step_decode(struct bContext *C,
                                          struct Main *UNUSED(bmain),
                                          UndoStep *us_p,
-                                         int UNUSED(dir),
+                                         const eUndoStepDir UNUSED(dir),
                                          bool UNUSED(is_final))
 {
   Depsgraph *depsgraph = CTX_data_depsgraph_pointer(C);