Warn user when OUTLINE_IN/OUT is about to flatten the structure (#11178)

diff --git a/src/Text3.cpp b/src/Text3.cpp
index d077dde7d2e9d61520c32dcdb022cd50f0a39dfd..a45eb39b88bfe8aeef4004431c8733e288ac6446 100644 (file)
--- a/src/Text3.cpp
+++ b/src/Text3.cpp
@@ -560,6 +560,45 @@ static void outline(OutlineOp mode, Cursor & cur, Text * text)
                }
                case OutlineIn:
                case OutlineOut: {
+                       // We first iterate without actually doing something
+                       // in order to check whether the action flattens the structure.
+                       // If so, warn (#11178).
+                       ParagraphList::iterator cstart = start;
+                       bool strucchange = false;
+                       for (; cstart != finish; ++cstart) {
+                               toclevel = buf.text().getTocLevel(distance(bgn, cstart));
+                               if (toclevel == Layout::NOT_IN_TOC)
+                                       continue;
+       
+                               DocumentClass const & tc = buf.params().documentClass();
+                               int const newtoclevel =
+                                       (mode == OutlineIn ? toclevel + 1 : toclevel - 1);
+       
+                               bool found = false;
+                               for (auto const & lay : tc) {
+                                       if (lay.toclevel == newtoclevel
+                                           && lay.isNumHeadingLabelType()
+                                           && cstart->layout().isNumHeadingLabelType()) {
+                                               found = true;
+                                               break;
+                                       }
+                               }
+                               if (!found) {
+                                       strucchange = true;
+                                       break;
+                               }
+                       }
+                       if (strucchange
+                           && frontend::Alert::prompt(_("Action flattens document structure"),
+                                                      _("This action will cause some headings that have been "
+                                                        "on different level before to be on the same level "
+                                                        "since there is no more lower or higher heading level. "
+                                                        "Continue still?"),
+                                                      1, 1,
+                                                      _("&Yes, continue nonetheless"),
+                                                      _("&No, quit operation")) == 1)
+                               break;
+
                        pit_type const len = distance(start, finish);
                        buf.undo().recordUndo(cur, pit, pit + len - 1);
                        for (; start != finish; ++start) {