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.

15 files changed, 68 insertions, 46 deletions

diff --git a/source/blender/editors/armature/editarmature_undo.c b/source/blender/editors/armature/editarmature_undo.c
index c6d7d2eb869..337d1138b23 100644
--- a/source/blender/editors/armature/editarmature_undo.c
+++ b/source/blender/editors/armature/editarmature_undo.c
@@ -178,8 +178,11 @@ static bool armature_undosys_step_encode(struct bContext *C, struct Main *bmain,
   return true;
 }
 
-static void armature_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int UNUSED(dir), bool UNUSED(is_final))
+static void armature_undosys_step_decode(struct bContext *C,
+                                         struct Main *bmain,
+                                         UndoStep *us_p,
+                                         const eUndoStepDir UNUSED(dir),
+                                         bool UNUSED(is_final))
 {
   ArmatureUndoStep *us = (ArmatureUndoStep *)us_p;
 
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;
 
diff --git a/source/blender/editors/curve/editfont_undo.c b/source/blender/editors/curve/editfont_undo.c
index 8559234b62f..07f062e7a53 100644
--- a/source/blender/editors/curve/editfont_undo.c
+++ b/source/blender/editors/curve/editfont_undo.c
@@ -356,8 +356,11 @@ static bool font_undosys_step_encode(struct bContext *C, struct Main *bmain, Und
   return true;
 }
 
-static void font_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int UNUSED(dir), bool UNUSED(is_final))
+static void font_undosys_step_decode(struct bContext *C,
+                                     struct Main *bmain,
+                                     UndoStep *us_p,
+                                     const eUndoStepDir UNUSED(dir),
+                                     bool UNUSED(is_final))
 {
   /* TODO(campbell): undo_system: use low-level API to set mode. */
   ED_object_mode_set_ex(C, OB_MODE_EDIT, false, NULL);
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;
diff --git a/source/blender/editors/include/ED_gpencil.h b/source/blender/editors/include/ED_gpencil.h
index acaa6495ba9..0136d599e8a 100644
--- a/source/blender/editors/include/ED_gpencil.h
+++ b/source/blender/editors/include/ED_gpencil.h
@@ -62,6 +62,8 @@ struct bAnimContext;
 struct wmKeyConfig;
 struct wmOperator;
 
+enum eUndoStepDir;
+
 #define GPENCIL_MINIMUM_JOIN_DIST 20.0f
 
 /* Reproject stroke modes. */
@@ -213,7 +215,7 @@ bool ED_gpencil_anim_copybuf_paste(struct bAnimContext *ac, const short copy_mod
 
 /* ------------ Grease-Pencil Undo System ------------------ */
 int ED_gpencil_session_active(void);
-int ED_undo_gpencil_step(struct bContext *C, const int step);
+int ED_undo_gpencil_step(struct bContext *C, const enum eUndoStepDir step);
 
 /* ------------ Grease-Pencil Armature ------------------ */
 bool ED_gpencil_add_armature(const struct bContext *C,
diff --git a/source/blender/editors/lattice/editlattice_undo.c b/source/blender/editors/lattice/editlattice_undo.c
index 3a5734706f1..3ffbc3712fc 100644
--- a/source/blender/editors/lattice/editlattice_undo.c
+++ b/source/blender/editors/lattice/editlattice_undo.c
@@ -212,8 +212,11 @@ static bool lattice_undosys_step_encode(struct bContext *C, Main *bmain, UndoSte
   return true;
 }
 
-static void lattice_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int UNUSED(dir), bool UNUSED(is_final))
+static void lattice_undosys_step_decode(struct bContext *C,
+                                        struct Main *bmain,
+                                        UndoStep *us_p,
+                                        const eUndoStepDir UNUSED(dir),
+                                        bool UNUSED(is_final))
 {
   LatticeUndoStep *us = (LatticeUndoStep *)us_p;
 
diff --git a/source/blender/editors/mesh/editmesh_undo.c b/source/blender/editors/mesh/editmesh_undo.c
index 1cbbbccdfa9..83de760aaa0 100644
--- a/source/blender/editors/mesh/editmesh_undo.c
+++ b/source/blender/editors/mesh/editmesh_undo.c
@@ -744,8 +744,11 @@ static bool mesh_undosys_step_encode(struct bContext *C, struct Main *bmain, Und
   return true;
 }
 
-static void mesh_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int UNUSED(dir), bool UNUSED(is_final))
+static void mesh_undosys_step_decode(struct bContext *C,
+                                     struct Main *bmain,
+                                     UndoStep *us_p,
+                                     const eUndoStepDir UNUSED(dir),
+                                     bool UNUSED(is_final))
 {
   MeshUndoStep *us = (MeshUndoStep *)us_p;
 
diff --git a/source/blender/editors/metaball/editmball_undo.c b/source/blender/editors/metaball/editmball_undo.c
index cbc60bcc031..b817bc3a718 100644
--- a/source/blender/editors/metaball/editmball_undo.c
+++ b/source/blender/editors/metaball/editmball_undo.c
@@ -187,8 +187,11 @@ static bool mball_undosys_step_encode(struct bContext *C, struct Main *bmain, Un
   return true;
 }
 
-static void mball_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int UNUSED(dir), bool UNUSED(is_final))
+static void mball_undosys_step_decode(struct bContext *C,
+                                      struct Main *bmain,
+                                      UndoStep *us_p,
+                                      const eUndoStepDir UNUSED(dir),
+                                      bool UNUSED(is_final))
 {
   MBallUndoStep *us = (MBallUndoStep *)us_p;
 
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);
diff --git a/source/blender/editors/sculpt_paint/paint_curve_undo.c b/source/blender/editors/sculpt_paint/paint_curve_undo.c
index a8e22f66734..dbe522bf304 100644
--- a/source/blender/editors/sculpt_paint/paint_curve_undo.c
+++ b/source/blender/editors/sculpt_paint/paint_curve_undo.c
@@ -126,7 +126,7 @@ static bool paintcurve_undosys_step_encode(struct bContext *C,
 static void paintcurve_undosys_step_decode(struct bContext *UNUSED(C),
                                            struct Main *UNUSED(bmain),
                                            UndoStep *us_p,
-                                           int UNUSED(dir),
+                                           const eUndoStepDir UNUSED(dir),
                                            bool UNUSED(is_final))
 {
   PaintCurveUndoStep *us = (PaintCurveUndoStep *)us_p;
diff --git a/source/blender/editors/sculpt_paint/sculpt_undo.c b/source/blender/editors/sculpt_paint/sculpt_undo.c
index 938080b392d..ec103bd2b98 100644
--- a/source/blender/editors/sculpt_paint/sculpt_undo.c
+++ b/source/blender/editors/sculpt_paint/sculpt_undo.c
@@ -1527,9 +1527,14 @@ static void sculpt_undosys_step_decode_redo(struct bContext *C,
   }
 }
 
-static void sculpt_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int dir, bool UNUSED(is_final))
+static void sculpt_undosys_step_decode(struct bContext *C,
+                                       struct Main *bmain,
+                                       UndoStep *us_p,
+                                       const eUndoStepDir dir,
+                                       bool UNUSED(is_final))
 {
+  BLI_assert(dir != STEP_INVALID);
+
   Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
 
   /* Ensure sculpt mode. */
@@ -1568,10 +1573,10 @@ static void sculpt_undosys_step_decode(
   }
 
   SculptUndoStep *us = (SculptUndoStep *)us_p;
-  if (dir < 0) {
+  if (dir == STEP_UNDO) {
     sculpt_undosys_step_decode_undo(C, depsgraph, us);
   }
-  else {
+  else if (dir == STEP_REDO) {
     sculpt_undosys_step_decode_redo(C, depsgraph, us);
   }
 }
diff --git a/source/blender/editors/space_image/image_undo.c b/source/blender/editors/space_image/image_undo.c
index 1d5725033e0..391c68f4231 100644
--- a/source/blender/editors/space_image/image_undo.c
+++ b/source/blender/editors/space_image/image_undo.c
@@ -947,13 +947,15 @@ static void image_undosys_step_decode_redo(ImageUndoStep *us)
 }
 
 static void image_undosys_step_decode(
-    struct bContext *C, struct Main *bmain, UndoStep *us_p, int dir, bool is_final)
+    struct bContext *C, struct Main *bmain, UndoStep *us_p, const eUndoStepDir dir, bool is_final)
 {
+  BLI_assert(dir != STEP_INVALID);
+
   ImageUndoStep *us = (ImageUndoStep *)us_p;
-  if (dir < 0) {
+  if (dir == STEP_UNDO) {
     image_undosys_step_decode_undo(us, is_final);
   }
-  else {
+  else if (dir == STEP_REDO) {
     image_undosys_step_decode_redo(us);
   }
 
diff --git a/source/blender/editors/space_text/text_undo.c b/source/blender/editors/space_text/text_undo.c
index 61b786b2b13..f55db8c3cc9 100644
--- a/source/blender/editors/space_text/text_undo.c
+++ b/source/blender/editors/space_text/text_undo.c
@@ -196,14 +196,19 @@ static bool text_undosys_step_encode(struct bContext *C,
   return true;
 }
 
-static void text_undosys_step_decode(
-    struct bContext *C, struct Main *UNUSED(bmain), UndoStep *us_p, int dir, bool is_final)
+static void text_undosys_step_decode(struct bContext *C,
+                                     struct Main *UNUSED(bmain),
+                                     UndoStep *us_p,
+                                     const eUndoStepDir dir,
+                                     bool is_final)
 {
+  BLI_assert(dir != STEP_INVALID);
+
   TextUndoStep *us = (TextUndoStep *)us_p;
   Text *text = us->text_ref.ptr;
 
   TextState *state;
-  if ((us->states[0].buf_array_state != NULL) && (dir == -1) && !is_final) {
+  if ((us->states[0].buf_array_state != NULL) && (dir == STEP_UNDO) && !is_final) {
     state = &us->states[0];
   }
   else {
diff --git a/source/blender/editors/undo/ed_undo.c b/source/blender/editors/undo/ed_undo.c
index 0771d0254e8..baa178a6a94 100644
--- a/source/blender/editors/undo/ed_undo.c
+++ b/source/blender/editors/undo/ed_undo.c
@@ -70,15 +70,6 @@
 /** We only need this locally. */
 static CLG_LogRef LOG = {"ed.undo"};
 
-/**
- * \warning Values are used in #ED_undo_gpencil_step,
- * which should eventually be replaced with the undo-system.
- */
-enum eUndoStepDir {
-  STEP_REDO = 1,
-  STEP_UNDO = -1,
-};
-
 /* -------------------------------------------------------------------- */
 /** \name Generic Undo System Access
  *
@@ -276,7 +267,7 @@ static int ed_undo_step_direction(bContext *C, enum eUndoStepDir step, ReportLis
    * FIXME: However, it seems to never be used in current code (`ED_gpencil_session_active` seems
    * to always return false). */
   if (ED_gpencil_session_active()) {
-    return ED_undo_gpencil_step(C, (int)step);
+    return ED_undo_gpencil_step(C, step);
   }
 
   wmWindowManager *wm = CTX_wm_manager(C);
diff --git a/source/blender/editors/undo/memfile_undo.c b/source/blender/editors/undo/memfile_undo.c
index eea0f29d295..51859b6a555 100644
--- a/source/blender/editors/undo/memfile_undo.c
+++ b/source/blender/editors/undo/memfile_undo.c
@@ -145,19 +145,18 @@ static int memfile_undosys_step_id_reused_cb(LibraryIDLinkCallbackData *cb_data)
 static void memfile_undosys_step_decode(struct bContext *C,
                                         struct Main *bmain,
                                         UndoStep *us_p,
-                                        int undo_direction,
+                                        const eUndoStepDir undo_direction,
                                         bool UNUSED(is_final))
 {
-  BLI_assert(undo_direction != 0);
+  BLI_assert(undo_direction != STEP_INVALID);
 
   bool use_old_bmain_data = true;
 
   if (USER_EXPERIMENTAL_TEST(&U, use_undo_legacy)) {
     use_old_bmain_data = false;
   }
-  else if (undo_direction > 0) {
-    /* Redo case.
-     * The only time we should have to force a complete redo is when current step is tagged as a
+  else if (undo_direction == STEP_REDO) {
+    /* The only time we should have to force a complete redo is when current step is tagged as a
      * redo barrier.
      * If previous step was not a memfile one should not matter here, current data in old bmain
      * should still always be valid for unchanged data-blocks. */
@@ -165,9 +164,8 @@ static void memfile_undosys_step_decode(struct bContext *C,
       use_old_bmain_data = false;
     }
   }
-  else {
-    /* Undo case.
-     * Here we do not care whether current step is an undo barrier, since we are coming from
+  else if (undo_direction == STEP_UNDO) {
+    /* Here we do not care whether current step is an undo barrier, since we are coming from
      * 'the future' we can still re-use old data. However, if *next* undo step
      * (i.e. the one immediately in the future, the one we are coming from)
      * is a barrier, then we have to force a complete undo.