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/blenloader/intern/readfile.h b/source/blender/blenloader/intern/readfile.h
index 86f05eda7b7..e007d42b283 100644
--- a/source/blender/blenloader/intern/readfile.h
+++ b/source/blender/blenloader/intern/readfile.h
@@ -91,7 +91,7 @@ typedef struct FileData {
   struct MemFile *memfile;
   /** Whether we are undoing (< 0) or redoing (> 0), used to choose which 'unchanged' flag to use
    * to detect unchanged data from memfile. */
-  short undo_direction;
+  int undo_direction; /* eUndoStepDir */
 
   /** Variables needed for reading from file. */
   gzFile gzfiledes;