Added the tentative undo feature. This is useful for IMEs that want to display

and manipulate a character being composed, but may then commit or remove it
leaving no history in undo of the intermediate forms.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/CellBuffer.h b/src/CellBuffer.h
index f07b45983..5e4fc7c8c 100644
--- a/src/CellBuffer.h
+++ b/src/CellBuffer.h
@@ -95,6 +95,7 @@ class UndoHistory {
 	int currentAction;
 	int undoSequenceDepth;
 	int savePoint;
+	int tentativePoint;
 
 	void EnsureUndoRoom();
 
@@ -117,6 +118,12 @@ public:
 	void SetSavePoint();
 	bool IsSavePoint() const;
 
+	// Tentative actions are used for input composition so that it can be undone cleanly
+	void TentativeStart();
+	void TentativeCommit();
+	bool TentativeActive() const { return tentativePoint >= 0; }
+	int TentativeSteps();
+
 	/// To perform an undo, StartUndo is called to retrieve the number of steps, then UndoStep is
 	/// called that many times. Similarly for redo.
 	bool CanUndo() const;
@@ -193,6 +200,11 @@ public:
 	void SetSavePoint();
 	bool IsSavePoint() const;
 
+	void TentativeStart();
+	void TentativeCommit();
+	bool TentativeActive() const;
+	int TentativeSteps();
+
 	bool SetUndoCollection(bool collectUndo);
 	bool IsCollectingUndo() const;
 	void BeginUndoAction();