PyAPI: add undo redo handlers

Useful so Python can clean up before/after undo steps.

1 files changed, 37 insertions, 2 deletions

diff --git a/source/blender/editors/undo/ed_undo.c b/source/blender/editors/undo/ed_undo.c
index 5f5b7b330f9..b4268dac863 100644
--- a/source/blender/editors/undo/ed_undo.c
+++ b/source/blender/editors/undo/ed_undo.c
@@ -38,6 +38,8 @@
 #include "DNA_scene_types.h"
 
 #include "BLI_utildefines.h"
+#include "BLI_callbacks.h"
+#include "BLI_listbase.h"
 
 #include "BLT_translation.h"
 
@@ -119,17 +121,50 @@ static int ed_undo_step(bContext *C, int step, const char *undoname)
 		return ED_undo_gpencil_step(C, step, undoname);
 	}
 
+	UndoStep *step_data_from_name = NULL;
+	int step_for_callback = step;
+	if (undoname != NULL) {
+		step_data_from_name = BKE_undosys_step_find_by_name(wm->undo_stack, undoname);
+		if (step_data_from_name == NULL) {
+			return OPERATOR_CANCELLED;
+		}
+
+		/* TODO(campbell), could use simple optimization. */
+		BLI_assert(step_data_from_name != wm->undo_stack->step_active);
+		step_for_callback = (
+		        BLI_findindex(&wm->undo_stack->steps, step_data_from_name) <
+		        BLI_findindex(&wm->undo_stack->steps, wm->undo_stack->step_active)) ? 1 : -1;
+	}
+
+	/* App-Handlers (pre). */
+	{
+		/* Note: ignore grease pencil for now. */
+		Main *bmain = CTX_data_main(C);
+		wm->op_undo_depth++;
+		BLI_callback_exec(bmain, &scene->id, (step_for_callback > 0) ? BLI_CB_EVT_UNDO_PRE : BLI_CB_EVT_REDO_PRE);
+		wm->op_undo_depth--;
+	}
+
+
 	/* Undo System */
 	{
 		if (undoname) {
-			UndoStep *step_data = BKE_undosys_step_find_by_name(wm->undo_stack, undoname);
-			BKE_undosys_step_undo_with_data(wm->undo_stack, C, step_data);
+			BKE_undosys_step_undo_with_data(wm->undo_stack, C, step_data_from_name);
 		}
 		else {
 			BKE_undosys_step_undo_compat_only(wm->undo_stack, C, step);
 		}
 	}
 
+	/* App-Handlers (post). */
+	{
+		Main *bmain = CTX_data_main(C);
+		scene = CTX_data_scene(C);
+		wm->op_undo_depth++;
+		BLI_callback_exec(bmain, &scene->id, step_for_callback > 0 ? BLI_CB_EVT_UNDO_PRE : BLI_CB_EVT_REDO_PRE);
+		wm->op_undo_depth--;
+	}
+
 	WM_event_add_notifier(C, NC_WINDOW, NULL);
 	WM_event_add_notifier(C, NC_WM | ND_UNDO, NULL);