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, 1 insertions, 0 deletions

diff --git a/source/blender/editors/space_text/CMakeLists.txt b/source/blender/editors/space_text/CMakeLists.txt
index 39b48f5b52c..91420a5d63a 100644
--- a/source/blender/editors/space_text/CMakeLists.txt
+++ b/source/blender/editors/space_text/CMakeLists.txt
@@ -48,6 +48,7 @@ set(SRC
 	text_format_py.c
 	text_header.c
 	text_ops.c
+	text_undo.c
 
 	text_format.h
 	text_intern.h