It is not possible to rely only on the interp result. A list of indices has to be built as a return value to undo/redo because there can be several edits between two separators and all such edits have to report which range of text they changed. Note: this commit does not deal with refcounts, it is very likely wrong in that respect.

3 files changed, 43 insertions, 18 deletions

diff --git a/generic/tkText.c b/generic/tkText.c
index d101364..60e726f 100644
--- a/generic/tkText.c
+++ b/generic/tkText.c
@@ -395,8 +395,8 @@ static int		DumpSegment(TkText *textPtr, Tcl_Interp *interp,
 			    const char *key, const char *value,
 			    Tcl_Obj *command, const TkTextIndex *index,
 			    int what);
-static int		TextEditUndo(TkText *textPtr);
-static int		TextEditRedo(TkText *textPtr);
+static int		TextEditUndo(TkText *textPtr, Tcl_Obj *rangesObj);
+static int		TextEditRedo(TkText *textPtr, Tcl_Obj *rangesObj);
 static Tcl_Obj *	TextGetText(const TkText *textPtr,
 			    const TkTextIndex *index1,
 			    const TkTextIndex *index2, int visibleOnly);
@@ -5060,7 +5060,7 @@ DumpSegment(
  *	Undo the last change.
  *
  * Results:
- *	None.
+ *	The ranges of text that were changed by the undo operation.
  *
  * Side effects:
  *	Apart from manipulating the undo and redo stacks, the state of the
@@ -5071,7 +5071,8 @@ DumpSegment(
 
 static int
 TextEditUndo(
-    TkText *textPtr)		/* Overall information about text widget. */
+    TkText *textPtr,		/* Overall information about text widget. */
+    Tcl_Obj *rangesObj)         /* Ranges of text that were changed. */
 {
     int status;
 
@@ -5090,7 +5091,7 @@ TextEditUndo(
 	textPtr->sharedTextPtr->dirtyMode = TK_TEXT_DIRTY_UNDO;
     }
 
-    status = TkUndoRevert(textPtr->sharedTextPtr->undoStack);
+    status = TkUndoRevert(textPtr->sharedTextPtr->undoStack, rangesObj);
 
     if (textPtr->sharedTextPtr->dirtyMode != TK_TEXT_DIRTY_FIXED) {
 	textPtr->sharedTextPtr->dirtyMode = TK_TEXT_DIRTY_NORMAL;
@@ -5108,7 +5109,7 @@ TextEditUndo(
  *	Redo the last undone change.
  *
  * Results:
- *	None.
+ *	The ranges of text that were changed by the undo operation.
  *
  * Side effects:
  *	Apart from manipulating the undo and redo stacks, the state of the
@@ -5119,7 +5120,8 @@ TextEditUndo(
 
 static int
 TextEditRedo(
-    TkText *textPtr)		/* Overall information about text widget. */
+    TkText *textPtr,		/* Overall information about text widget. */
+    Tcl_Obj *rangesObj)         /* Ranges of text that were changed. */
 {
     int status;
 
@@ -5138,7 +5140,7 @@ TextEditRedo(
 	textPtr->sharedTextPtr->dirtyMode = TK_TEXT_DIRTY_REDO;
     }
 
-    status = TkUndoApply(textPtr->sharedTextPtr->undoStack);
+    status = TkUndoApply(textPtr->sharedTextPtr->undoStack, rangesObj);
 
     if (textPtr->sharedTextPtr->dirtyMode != TK_TEXT_DIRTY_FIXED) {
 	textPtr->sharedTextPtr->dirtyMode = TK_TEXT_DIRTY_NORMAL;
@@ -5174,6 +5176,7 @@ TextEditCmd(
     int index, setModified, oldModified;
     int canRedo = 0;
     int canUndo = 0;
+    Tcl_Obj *rangesObj = Tcl_NewObj();
 
     static const char *const editOptionStrings[] = {
 	"canundo", "canredo", "modified", "redo", "reset", "separator",
@@ -5257,11 +5260,13 @@ TextEditCmd(
 	    return TCL_ERROR;
 	}
 	canUndo = TkUndoCanUndo(textPtr->sharedTextPtr->undoStack);
-        if (TextEditRedo(textPtr)) {
+        if (TextEditRedo(textPtr, rangesObj)) {
 	    Tcl_SetObjResult(interp, Tcl_NewStringObj("nothing to redo", -1));
 	    Tcl_SetErrorCode(interp, "TK", "TEXT", "NO_REDO", NULL);
 	    return TCL_ERROR;
-	}
+        } else {
+            Tcl_SetObjResult(interp, rangesObj);
+        }
         canRedo = TkUndoCanRedo(textPtr->sharedTextPtr->undoStack);
         if (!canUndo || !canRedo) {
             GenerateUndoStackEvent(textPtr);
@@ -5292,11 +5297,13 @@ TextEditCmd(
 	    return TCL_ERROR;
 	}
         canRedo = TkUndoCanRedo(textPtr->sharedTextPtr->undoStack);
-	if (TextEditUndo(textPtr)) {
+	if (TextEditUndo(textPtr, rangesObj)) {
 	    Tcl_SetObjResult(interp, Tcl_NewStringObj("nothing to undo", -1));
 	    Tcl_SetErrorCode(interp, "TK", "TEXT", "NO_UNDO", NULL);
 	    return TCL_ERROR;
-	}
+        } else {
+            Tcl_SetObjResult(interp, rangesObj);
+        }
         canUndo = TkUndoCanUndo(textPtr->sharedTextPtr->undoStack);
         if (!canRedo || !canUndo) {
             GenerateUndoStackEvent(textPtr);
diff --git a/generic/tkUndo.c b/generic/tkUndo.c
index c66905d..f364326 100644
--- a/generic/tkUndo.c
+++ b/generic/tkUndo.c
@@ -556,7 +556,8 @@ TkUndoInsertUndoSeparator(
  *	Undo a compound action on the stack.
  *
  * Results:
- *	A Tcl status code
+ *	A Tcl status code. Also, the passed Tcl_(List)Obj is appended by the
+ *	interp results from evaluation of each element of the undo stack.
  *
  * Side effects:
  *	None.
@@ -566,7 +567,8 @@ TkUndoInsertUndoSeparator(
 
 int
 TkUndoRevert(
-    TkUndoRedoStack *stack)
+    TkUndoRedoStack *stack,
+    Tcl_Obj *retObj)
 {
     TkUndoAtom *elem;
 
@@ -598,6 +600,13 @@ TkUndoRevert(
 
 	EvaluateActionList(stack->interp, elem->revert);
 
+        /*
+         * The interp result is appended to the returned object for each
+         * element of the undo stack (not for each sub-atom).
+         */
+
+        Tcl_ListObjAppendList(NULL, retObj, Tcl_GetObjResult(stack->interp));
+
 	TkUndoPushStack(&stack->redoStack, elem);
 	elem = TkUndoPopStack(&stack->undoStack);
     }
@@ -619,7 +628,8 @@ TkUndoRevert(
  *	Redo a compound action on the stack.
  *
  * Results:
- *	A Tcl status code
+ *	A Tcl status code. Also, the passed Tcl_(List)Obj is appended by the
+ *	interp results from evaluation of each element of the redo stack.
  *
  * Side effects:
  *	None.
@@ -629,7 +639,8 @@ TkUndoRevert(
 
 int
 TkUndoApply(
-    TkUndoRedoStack *stack)
+    TkUndoRedoStack *stack,
+    Tcl_Obj *retObj)
 {
     TkUndoAtom *elem;
 
@@ -660,6 +671,13 @@ TkUndoApply(
 
 	EvaluateActionList(stack->interp, elem->apply);
 
+        /*
+         * The interp result is appended to the returned object for each
+         * element of the redo stack (not for each sub-atom).
+         */
+
+        Tcl_ListObjAppendList(NULL, retObj, Tcl_GetObjResult(stack->interp));
+
 	TkUndoPushStack(&stack->undoStack, elem);
 	elem = TkUndoPopStack(&stack->redoStack);
     }
diff --git a/generic/tkUndo.h b/generic/tkUndo.h
index 490ede9..505e0f0 100644
--- a/generic/tkUndo.h
+++ b/generic/tkUndo.h
@@ -109,7 +109,7 @@ MODULE_SCOPE TkUndoSubAtom *TkUndoMakeSubAtom(TkUndoProc *funcPtr,
 			    TkUndoSubAtom *subAtomList);
 MODULE_SCOPE void	TkUndoPushAction(TkUndoRedoStack *stack,
 			    TkUndoSubAtom *apply, TkUndoSubAtom *revert);
-MODULE_SCOPE int	TkUndoRevert(TkUndoRedoStack *stack);
-MODULE_SCOPE int	TkUndoApply(TkUndoRedoStack *stack);
+MODULE_SCOPE int	TkUndoRevert(TkUndoRedoStack *stack, Tcl_Obj *retObj);
+MODULE_SCOPE int	TkUndoApply(TkUndoRedoStack *stack, Tcl_Obj *retObj);
 
 #endif /* _TKUNDO */