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-rw-r--r--library/text.tcl13
1 files changed, 13 insertions, 0 deletions
diff --git a/library/text.tcl b/library/text.tcl
index f241abd..02a8939 100644
--- a/library/text.tcl
+++ b/library/text.tcl
@@ -1228,6 +1228,19 @@ proc ::tk::TextUndoRedoProcessMarks {w} {
# transform marks into indices
# the number of undo/redo marks is always even, each right mark
# completes a left mark to give a range
+ # this is true because:
+ # - undo/redo only deals with insertions and deletions of text
+ # - insertions may move marks but not delete them
+ # - when deleting text, marks located inside the deleted range
+ # are not erased but moved to the start of the deletion range
+ # . this is done in TkBTreeDeleteIndexRange ("This segment
+ # refuses to die...")
+ # . because MarkDeleteProc does nothing else than returning
+ # a value indicating that marks are not deleted by this
+ # deleteProc
+ # . mark deletion rather happen through [.text mark unset xxx]
+ # which was not used _up to this point of the code_ (it
+ # is a bit later just before exiting the present proc)
set nUndoMarks [llength $undoMarks]
set n [expr {$nUndoMarks / 2}]
set undoMarks [lsort -dictionary $undoMarks]