Undo: unified undo system w/ linear history

- Use a single undo history for all operations.
- UndoType's are registered and poll the context to check if they
  should be used when performing an undo push.
- Mode switching is used to ensure the state is correct before
  undo data is restored.
- Some undo types accumulate changes (image & text editing)
  others store the state multiple times (with de-duplication).
  This is supported by checking UndoStack.mode `ACCUMULATE` / `STORE`.
- Each undo step stores ID datablocks they use with utilities to help
  manage restoring correct ID's.
  Needed since global undo is now mixed with other modes undo.
- Currently performs each undo step when going up/down history
  Previously this wasn't done, making history fail in some cases.
  This can be optimized to skip some combinations of undo steps.

grease-pencil is an exception which has not been updated
since it integrates undo into the draw-session.

See D3113

1 files changed, 6 insertions, 4 deletions

diff --git a/source/blender/editors/sculpt_paint/paint_intern.h b/source/blender/editors/sculpt_paint/paint_intern.h
index 52be4be4c0d..63a12b3c145 100644
--- a/source/blender/editors/sculpt_paint/paint_intern.h
+++ b/source/blender/editors/sculpt_paint/paint_intern.h
@@ -55,6 +55,7 @@ struct wmOperator;
 struct wmOperatorType;
 struct wmWindowManager;
 struct DMCoNo;
+struct UndoStep;
 enum ePaintMode;
 
 /* paint_stroke.c */
@@ -221,15 +222,20 @@ void PAINT_OT_add_simple_uvs(struct wmOperatorType *ot);
 
 /* paint_image_undo.c */
 void *image_undo_find_tile(
+        ListBase *undo_tiles,
         struct Image *ima, struct ImBuf *ibuf, int x_tile, int y_tile,
         unsigned short **mask, bool validate);
 void *image_undo_push_tile(
+        ListBase *undo_tiles,
         struct Image *ima, struct ImBuf *ibuf, struct ImBuf **tmpibuf, int x_tile, int y_tile,
         unsigned short **, bool **valid, bool proj, bool find_prev);
 void image_undo_remove_masks(void);
 void image_undo_init_locks(void);
 void image_undo_end_locks(void);
 
+struct ListBase *ED_image_undosys_step_get_tiles(struct UndoStep *us_p);
+struct ListBase *ED_image_undo_get_tiles(void);
+
 /* sculpt_uv.c */
 int uv_sculpt_poll(struct bContext *C);
 int uv_sculpt_keymap_poll(struct bContext *C);
@@ -304,10 +310,6 @@ typedef enum {
 void set_brush_rc_props(struct PointerRNA *ptr, const char *paint, const char *prop, const char *secondary_prop,
                         RCFlags flags);
 
-/* paint_undo.c */
-struct ListBase *undo_paint_push_get_list(int type);
-void undo_paint_push_count_alloc(int type, int size);
-
 /* paint_hide.c */
 
 typedef enum {