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, 2 insertions, 6 deletions

diff --git a/source/blender/editors/physics/particle_object.c b/source/blender/editors/physics/particle_object.c
index d85720f956c..63b84df9fce 100644
--- a/source/blender/editors/physics/particle_object.c
+++ b/source/blender/editors/physics/particle_object.c
@@ -911,10 +911,7 @@ static void copy_particle_edit(Scene *scene, Object *ob, ParticleSystem *psys, P
 	
 	edit->emitter_field = NULL;
 	edit->emitter_cosnos = NULL;
-	
-	BLI_listbase_clear(&edit->undo);
-	edit->curundo = NULL;
-	
+
 	edit->points = MEM_dupallocN(edit_from->points);
 	pa = psys->particles;
 	LOOP_POINTS {
@@ -943,8 +940,7 @@ static void copy_particle_edit(Scene *scene, Object *ob, ParticleSystem *psys, P
 	recalc_lengths(edit);
 	recalc_emitter_field(ob, psys);
 	PE_update_object(scene, ob, true);
-	
-	PTCacheUndo_clear(edit);
+
 	PE_undo_push(scene, "Original");
 }