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, 4 insertions, 3 deletions

diff --git a/source/blender/editors/gpencil/gpencil_undo.c b/source/blender/editors/gpencil/gpencil_undo.c
index e545a3365e9..4e172104ce7 100644
--- a/source/blender/editors/gpencil/gpencil_undo.c
+++ b/source/blender/editors/gpencil/gpencil_undo.c
@@ -36,6 +36,7 @@
 #include "BKE_blender_undo.h"
 #include "BKE_context.h"
 #include "BKE_gpencil.h"
+#include "BKE_undo_system.h"
 
 #include "ED_gpencil.h"
 
@@ -61,19 +62,19 @@ int ED_gpencil_session_active(void)
   return (BLI_listbase_is_empty(&undo_nodes) == false);
 }
 
-int ED_undo_gpencil_step(bContext *C, const int step)
+int ED_undo_gpencil_step(bContext *C, const eUndoStepDir step)
 {
   bGPdata **gpd_ptr = NULL, *new_gpd = NULL;
 
   gpd_ptr = ED_gpencil_data_get_pointers(C, NULL);
 
-  if (step == -1) { /* undo */
+  if (step == STEP_UNDO) {
     if (cur_node->prev) {
       cur_node = cur_node->prev;
       new_gpd = cur_node->gpd;
     }
   }
-  else if (step == 1) {
+  else if (step == STEP_REDO) {
     if (cur_node->next) {
       cur_node = cur_node->next;
       new_gpd = cur_node->gpd;