diff --git a/cmake/qet_compilation_vars.cmake b/cmake/qet_compilation_vars.cmake
index 6f5cbd9b6..dfa30c109 100644
--- a/cmake/qet_compilation_vars.cmake
+++ b/cmake/qet_compilation_vars.cmake
@@ -899,6 +899,8 @@ set(QET_SRC_FILES
   ${QET_DIR}/sources/undocommand/groupitemscommand.h
   ${QET_DIR}/sources/undocommand/alignselectioncommand.cpp
   ${QET_DIR}/sources/undocommand/alignselectioncommand.h
+  ${QET_DIR}/sources/undocommand/mirrorselectioncommand.cpp
+  ${QET_DIR}/sources/undocommand/mirrorselectioncommand.h
   ${QET_DIR}/sources/undocommand/rotateselectioncommand.cpp
   ${QET_DIR}/sources/undocommand/rotateselectioncommand.h
   ${QET_DIR}/sources/undocommand/promoteshapecommand.cpp
diff --git a/misc/qet-mcp/qet_mcp.py b/misc/qet-mcp/qet_mcp.py
index d0aba37ea..f614ba98a 100755
--- a/misc/qet-mcp/qet_mcp.py
+++ b/misc/qet-mcp/qet_mcp.py
@@ -682,13 +682,18 @@ def tool_diff(before: str, after: str) -> dict:
         # the only thing a rotation changes, so without it a rotated symbol
         # reads as untouched.
         r["orientation"] = e.get("orientation", "0")
+        # A mirrored symbol carries mirror="horizontal", "vertical" or
+        # "both", about its own axes; a mirror changes nothing else unless
+        # the symbol's hotspot is off its centre.
+        r["mirror"] = e.get("mirror", "")
         a_el[r["uuid"] or f"{i}:{r['x']},{r['y']}:{r['name']}"] = r
     for i, e in _elements(_root(after)):
         r = _element_row(i, e)
         r["orientation"] = e.get("orientation", "0")
+        r["mirror"] = e.get("mirror", "")
         b_el[r["uuid"] or f"{i}:{r['x']},{r['y']}:{r['name']}"] = r
 
-    moved, rotated, relabelled, changed_info = [], [], [], []
+    moved, rotated, mirrored, relabelled, changed_info = [], [], [], [], []
     for k, a in a_el.items():
         b = b_el.get(k)
         if b is None:
@@ -696,6 +701,9 @@ def tool_diff(before: str, after: str) -> dict:
         if a["orientation"] != b["orientation"]:
             rotated.append({"uuid": k, "name": a["name"], "folio": a["folio"],
                             "orientation": [a["orientation"], b["orientation"]]})
+        if a["mirror"] != b["mirror"]:
+            mirrored.append({"uuid": k, "name": a["name"], "folio": a["folio"],
+                             "mirror": [a["mirror"], b["mirror"]]})
         if (a["x"], a["y"]) != (b["x"], b["y"]):
             moved.append({
                 "uuid": k, "name": a["name"], "folio": a["folio"],
@@ -764,6 +772,7 @@ def tool_diff(before: str, after: str) -> dict:
             "relabelled": relabelled[:50],
             "info_changed": changed_info[:50],
             "rotated": rotated[:50],
+            "mirrored": mirrored[:50],
         },
         "conductors": {
             "before": len(a_co), "after": len(b_co),
@@ -1401,6 +1410,8 @@ OPS = {
                                                  ("dx", "num"), ("dy", "num")]),
     "rotate_element":   ("rotateElement",       [("folio", "folio"), ("element", "elmt"),
                                                  ("angle", "num")]),
+    "mirror_element":   ("mirrorElement",       [("folio", "folio"), ("element", "elmt"),
+                                                 ("vertical", "bool")]),
     "set_label":        ("setElementLabel",     [("folio", "folio"), ("element", "elmt"),
                                                  ("label", "str")]),
     "set_info":         ("setElementInfo",      [("folio", "folio"), ("element", "elmt"),
diff --git a/misc/qet-mcp/test_qet_mcp.py b/misc/qet-mcp/test_qet_mcp.py
index 173cb034a..4582e19da 100644
--- a/misc/qet-mcp/test_qet_mcp.py
+++ b/misc/qet-mcp/test_qet_mcp.py
@@ -379,6 +379,7 @@ class EditValidation(unittest.TestCase):
             "set_position": el + [{"op": "set_position", "folio": "$f", "element": "$e", "x": 1, "y": 1}],
             "move_element": el + [{"op": "move_element", "folio": "$f", "element": "$e", "dx": 1, "dy": 1}],
             "rotate_element": el + [{"op": "rotate_element", "folio": "$f", "element": "$e", "angle": 90}],
+            "mirror_element": el + [{"op": "mirror_element", "folio": "$f", "element": "$e", "vertical": False}],
             "set_label": el + [{"op": "set_label", "folio": "$f", "element": "$e", "label": "K"}],
             "set_info": el + [{"op": "set_info", "folio": "$f", "element": "$e", "key": "k", "value": "v"}],
             "add_conductor": two + [{"op": "add_conductor", "folio": "$f", "from": "$e", "from_terminal": 0,
@@ -2065,13 +2066,13 @@ class DiffContracts(unittest.TestCase):
             "relabelled": [{"uuid": A, "name": "coil", "from": "K1", "to": "K2"}],
             "info_changed": [{"uuid": A, "name": "coil", "from": {"label": "K1", "comment": "c"},
                               "to": {"label": "K2", "comment": "d"}}],
-            "rotated": []})
+            "rotated": [], "mirrored": []})
 
     def test_an_unchanged_element_reports_nothing(self):
         p = self.qet(self.folio(self.el(self.A, 1, 2, "K1", "c")))
         e = m.tool_diff(p, p)["elements"]
         self.assertEqual((e["moved"], e["relabelled"], e["info_changed"], e["added"], e["removed"],
-                          e["rotated"]), ([], [], [], [], [], []))
+                          e["rotated"], e["mirrored"]), ([], [], [], [], [], [], []))
 
     def test_equal_angles_written_differently_are_the_same(self):
         self.assertEqual([m._angle(v) for v in ("-270", "90", "-90", "270", "360", "0", "450", "12.5", "", "x")],
@@ -2098,6 +2099,18 @@ class DiffContracts(unittest.TestCase):
         plain = self.qet(self.folio(self.el(self.A, 1, 2)))
         self.assertEqual(m.tool_diff(plain, rot(0))["elements"]["rotated"], [])
 
+    def test_a_mirror_is_reported(self):
+        """A mirror of a symbol changes its mirror attribute, which is absent
+        when the symbol is not mirrored."""
+        plain = self.qet(self.folio(self.el(self.A, 1, 2)))
+        mirrored = self.qet(self.folio(
+            self.el(self.A, 1, 2).replace('x="1"', 'mirror="horizontal" x="1"')))
+        d = m.tool_diff(plain, mirrored)
+        self.assertEqual(d["elements"]["mirrored"],
+                         [{"uuid": self.A, "name": "coil", "folio": 1, "mirror": ["", "horizontal"]}])
+        self.assertEqual((d["elements"]["moved"], d["elements"]["rotated"]), ([], []))
+        self.assertEqual(m.tool_diff(plain, plain)["elements"]["mirrored"], [])
+
     def test_conductors_section_exact(self):
         A, B, C = self.A, self.B, self.C
         els = self.el(A, 0, 0) + self.el(B, 0, 0) + self.el(C, 0, 0)
diff --git a/sources/dxfexport.cpp b/sources/dxfexport.cpp
index 397c6d30d..d61041d58 100644
--- a/sources/dxfexport.cpp
+++ b/sources/dxfexport.cpp
@@ -38,6 +38,7 @@
 #include "qetinformation.h"
 #include "textlines.h"
 
+#include <QFontMetricsF>
 #include <QGraphicsSimpleTextItem>
 #include <QSet>
 #include <cmath>
@@ -48,14 +49,22 @@ namespace {
 		Draw the drawing of @a elmt's definition: its static texts, lines,
 		rectangles, circles, polygons and arcs, and its terminals when
 		@a draw_terminals, as if it were placed at @a elem_pos_x,
-		@a elem_pos_y and turned @a rotation_angle degrees. Used for every
-		symbol drawn in full, and once per block for a block's content.
+		@a elem_pos_y and turned @a rotation_angle degrees, with @a elmt's
+		mirrors when @a mirrored. Used for every symbol drawn in full, and
+		once per block for a block's content.
 	*/
 	void drawSymbol(const QString &file_path, Element *elmt,
 					qreal elem_pos_x, qreal elem_pos_y,
-					double rotation_angle, bool draw_terminals)
+					double rotation_angle, bool draw_terminals,
+					bool mirrored = false)
 	{
 		using namespace DxfExport;
+			//The mirrors of an element are about its own axes, before it is
+			//rotated, see Element::setMirror()
+		const bool mirror_h = mirrored && elmt -> hasHorizontalMirror();
+		const bool mirror_v = mirrored && elmt -> hasVerticalMirror();
+		const qreal mirror_x = mirror_h ? -1 : 1;
+		const qreal mirror_y = mirror_v ? -1 : 1;
 		ElementPictureFactory::primitives primitives = ElementPictureFactory::instance()->getPrimitives(elmt->location());
 
 		Createdxf::layer = Layer::SymbolTexts;
@@ -65,8 +74,26 @@ namespace {
 			if (fontSize < 0)
 				fontSize = text->font().pixelSize();
 
-			qreal x = elem_pos_x + text->pos().x();
-			qreal y = elem_pos_y + text->pos().y();
+			QPointF text_pos = text->pos();
+			if (mirror_h || mirror_v)
+			{
+					//The text keeps reading normally: only its box is
+					//mirrored, about its own centre, as ElementPictureFactory
+					//draws it on the folio
+				QTransform box_transform;
+				box_transform.translate(text->pos().x(), text->pos().y());
+				box_transform.rotate(text->rotation());
+				const QFontMetricsF metrics(text->font());
+				const QRectF box(0, -metrics.ascent(),
+								 text->boundingRect().width(),
+								 text->boundingRect().height());
+				const QPointF centre = box_transform.mapRect(box).center();
+				text_pos += QPointF(centre.x() * (mirror_x - 1),
+									centre.y() * (mirror_y - 1));
+			}
+
+			qreal x = elem_pos_x + text_pos.x();
+			qreal y = elem_pos_y + text_pos.y();
 
 			qreal angle = text -> rotation() + rotation_angle;
 			qreal angler = angle * M_PI/180;
@@ -91,21 +118,21 @@ namespace {
 		Createdxf::layer = Layer::Symbols;
 		for (QLineF line : primitives.m_lines)
 		{
-			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle);
+			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle).scale(mirror_x, mirror_y);
 			QLineF l = t.map(line);
 			Createdxf::drawLine(file_path, l, 0);
 		}
 
 		for (QRectF rect : primitives.m_rectangles)
 		{
-			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle);
+			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle).scale(mirror_x, mirror_y);
 			QRectF r = t.mapRect(rect);
 			Createdxf::drawRectangle(file_path,r,0);
 		}
 
 		for (QRectF circle_rect : primitives.m_circles)
 		{
-			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle);
+			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle).scale(mirror_x, mirror_y);
 			QPointF c = t.map(QPointF(circle_rect.center().x(),circle_rect.center().y()));
 			Createdxf::drawCircle(file_path,c,circle_rect.width()/2,0);
 		}
@@ -114,7 +141,7 @@ namespace {
 		{
 			if (polygon.size() == 0)
 				continue;
-			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle);
+			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle).scale(mirror_x, mirror_y);
 			QPolygonF poly = t.map(polygon);
 			if(poly.isClosed())
 				Createdxf::drawPolygon(file_path,poly,0);
@@ -133,6 +160,18 @@ namespace {
 			qreal h = arc.at(3);
 			qreal startAngle = arc.at(4);
 			qreal spanAngle = arc .at(5);
+				//In a mirror the arc starts where it ended: an angle a
+				//becomes 180 - a in a horizontal one, -a in a vertical one
+			if (mirror_h)
+			{
+				x = elem_pos_x - arc.at(0) - w;
+				startAngle = 180 - startAngle - spanAngle;
+			}
+			if (mirror_v)
+			{
+				y = elem_pos_y - arc.at(1) - h;
+				startAngle = -startAngle - spanAngle;
+			}
 			QRectF r(x,y,w,h);
 			QPointF hotspot(elem_pos_x,elem_pos_y);
 			Createdxf::drawArcEllipse(file_path, r, startAngle, spanAngle, hotspot, rotation_angle, 0);
@@ -142,7 +181,7 @@ namespace {
 			// Draw terminals
 			QList<Terminal *> list_terminals = elmt->terminals();
 			QColor col("red");
-			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle);
+			QTransform t = QTransform().translate(elem_pos_x,elem_pos_y).rotate(rotation_angle).scale(mirror_x, mirror_y);
 			foreach(Terminal *tp, list_terminals) {
 				QPointF c = t.map(QPointF(tp->dock_elmt_.x(),tp->dock_elmt_.y()));
 				Createdxf::drawCircle(file_path,c,3.0,Createdxf::dxfColor(col));
@@ -345,7 +384,7 @@ void DxfExport::write(Diagram *diagram, int width, int height,
 		QSet<QString> used;
 		for (Element *elmt : std::as_const(list_elements)) {
 			const QString key = elmt -> location().toString();
-			if (block_names.contains(key)
+			if (elmt -> isMirrored() || block_names.contains(key)
 				|| drawsNothing(elmt, properties.draw_terminals))
 				continue;
 			QString file_name = elmt -> location().fileName();
@@ -363,6 +402,14 @@ void DxfExport::write(Diagram *diagram, int width, int height,
 			block_models << elmt;
 		}
 	}
+		//A mirrored symbol is drawn in full: an INSERT with a negative
+		//scale would mirror its texts too, which QElectroTech keeps
+		//readable
+	const auto blockOf = [&block_names](Element *elmt) {
+		return elmt -> isMirrored()
+				? QString()
+				: block_names.value(elmt -> location().toString());
+	};
 
 		//With dxf_attributes, a symbol's own texts (its label, its
 		//function...) become attributes of its INSERT, written where the
@@ -384,9 +431,7 @@ void DxfExport::write(Diagram *diagram, int width, int height,
 				break;
 			auto *deti = qgraphicsitem_cast<DynamicElementTextItem *>(dti);
 			Element *elmt = deti ? deti -> parentElement() : nullptr;
-			const QString block = elmt
-					? block_names.value(elmt -> location().toString())
-					: QString();
+			const QString block = elmt ? blockOf(elmt) : QString();
 			if (block.isEmpty())
 				continue;
 
@@ -445,7 +490,7 @@ void DxfExport::write(Diagram *diagram, int width, int height,
 			//repeated; the label formula is how the label is made, not
 			//part data.
 		for (Element *elmt : std::as_const(list_elements)) {
-			const QString block = block_names.value(elmt -> location().toString());
+			const QString block = blockOf(elmt);
 			if (block.isEmpty())
 				continue;
 			const DiagramContext information = elmt -> elementInformations();
@@ -525,10 +570,10 @@ void DxfExport::write(Diagram *diagram, int width, int height,
 		const qreal elem_pos_x = elmt -> pos().x();
 		const qreal elem_pos_y = elmt -> pos().y();
 
-		const QString block = block_names.value(elmt -> location().toString());
+		const QString block = blockOf(elmt);
 		if (block.isEmpty()) {
 			drawSymbol(file_path, elmt, elem_pos_x, elem_pos_y,
-					   rotation_angle, properties.draw_terminals);
+					   rotation_angle, properties.draw_terminals, true);
 		} else {
 			Createdxf::layer = Layer::Symbols;
 				//QElectroTech turns a symbol clockwise, DXF counter-clockwise
diff --git a/sources/factory/elementpicturefactory.cpp b/sources/factory/elementpicturefactory.cpp
index 2603d1bf5..d060f46d9 100644
--- a/sources/factory/elementpicturefactory.cpp
+++ b/sources/factory/elementpicturefactory.cpp
@@ -94,6 +94,40 @@ void ElementPictureFactory::getPictures(const ElementsLocation &location, QPictu
 	}
 }
 
+/**
+	@brief ElementPictureFactory::getMirroredPictures
+	Same as getPictures(), for an element mirrored on its folio
+	(Element::setMirror()). The drawing is the same; only the texts differ:
+	each one is drawn so that, once the element's mirror is applied, its box
+	lands mirrored but its letters still read normally.
+	@param location
+	@param horizontal : the element's left and right swap
+	@param vertical : the element's top and bottom swap
+	@param picture
+	@param low_picture
+*/
+void ElementPictureFactory::getMirroredPictures(const ElementsLocation &location,
+												bool horizontal,
+												bool vertical,
+												QPicture &picture,
+												QPicture &low_picture)
+{
+	if(!location.exist() || !(horizontal || vertical)) {
+		return;
+	}
+
+	const QPair<QUuid, int> key(cacheKey(location),
+								(horizontal ? 1 : 0) | (vertical ? 2 : 0));
+
+	if(!m_mirrored_pictures_H.contains(key)
+	   && !build(location, nullptr, nullptr,
+				 QTransform::fromScale(horizontal ? -1 : 1, vertical ? -1 : 1))) {
+		return;
+	}
+	picture = m_mirrored_pictures_H.value(key);
+	low_picture = m_mirrored_low_pictures_H.value(key);
+}
+
 /**
 	@brief ElementPictureFactory::dropCache
 	Forget the cached drawing of the element at @p location, so the next
@@ -113,6 +147,10 @@ void ElementPictureFactory::dropCache(const ElementsLocation &location)
 	const QUuid uuid = cacheKey(location);
 	m_pictures_H.remove(uuid);
 	m_low_pictures_H.remove(uuid);
+	for (int mirror = 1 ; mirror <= 3 ; ++mirror) {
+		m_mirrored_pictures_H.remove(qMakePair(uuid, mirror));
+		m_mirrored_low_pictures_H.remove(qMakePair(uuid, mirror));
+	}
 	m_pixmap_H.remove(uuid);
 		//The text items belong to the cache; nothing else holds them.
 	qDeleteAll(m_primitives_H.take(uuid).m_texts);
@@ -217,11 +255,16 @@ ElementPictureFactory::~ElementPictureFactory()
 	this function draw on it and don't store it.
 	if null, this function create a QPicture for normal and low zoom,
 	draw on it and store it in m_pictures_H and m_low_pictures_H
+	(m_mirrored_pictures_H and m_mirrored_low_pictures_H if @p mirror
+	is not the identity)
+	@param mirror : the mirror of an element to draw the drawing for, see
+	getMirroredPictures()
 	@return
 */
 bool ElementPictureFactory::build(const ElementsLocation &location,
 				  QPicture *picture,
-				  QPicture *low_picture)
+				  QPicture *low_picture,
+				  const QTransform &mirror)
 {
 	QDomElement dom = location.xml();
 
@@ -281,6 +324,8 @@ bool ElementPictureFactory::build(const ElementsLocation &location,
 	tmp.setCosmetic(true);
 	low_painter.setPen(tmp);
 
+	m_build_mirror = mirror;
+
 	//scroll of the Children of the Definition: Parts of the Drawing
 	// Extract PLC master data for rendering plc_table parts
 	QDomElement plc_master_data;
@@ -333,9 +378,24 @@ bool ElementPictureFactory::build(const ElementsLocation &location,
 		//End of the drawing
 	painter.end();
 	low_painter.end();
+	m_build_mirror = QTransform();
 	qDeleteAll(low_primitives.m_texts);
 
 	const auto uuid_ = cacheKey(location);
+	if (!mirror.isIdentity()) {
+			//The primitives are those of the drawing without mirror,
+			//already kept by the build of that one
+		qDeleteAll(primitives_.m_texts);
+		const QPair<QUuid, int> key(uuid_, (mirror.m11() < 0 ? 1 : 0)
+											| (mirror.m22() < 0 ? 2 : 0));
+		if (!picture) {
+			m_mirrored_pictures_H.insert(key, pic);
+		}
+		if (!low_picture) {
+			m_mirrored_low_pictures_H.insert(key, low_pic);
+		}
+		return true;
+	}
 	if (!picture) {
 		m_pictures_H.insert(uuid_, pic);
 		m_primitives_H.insert(uuid_, primitives_);
@@ -616,8 +676,6 @@ void ElementPictureFactory::parseText(const QDomElement &dom, QPainter &painter,
 	text_document.setPlainText(dom.attribute("text"));
 
 	painter.setTransform(QTransform(), false);
-	painter.translate(dom.attribute("x").toDouble(), dom.attribute("y").toDouble());
-	painter.rotate(dom.attribute("rotation", "0").toDouble());
 
 	/*
 		Moves the QPainter's coordinate system to render in the right place;
@@ -651,7 +709,25 @@ void ElementPictureFactory::parseText(const QDomElement &dom, QPainter &painter,
 		}
 	}
 
-	painter.translate(qpainter_offset);
+	QTransform text_transform;
+	text_transform.translate(dom.attribute("x").toDouble(), dom.attribute("y").toDouble());
+	text_transform.rotate(dom.attribute("rotation", "0").toDouble());
+	text_transform.translate(qpainter_offset.x(), qpainter_offset.y());
+
+	if (!m_build_mirror.isIdentity())
+	{
+			//The element is mirrored about its own axes when it is drawn.
+			//Mirror the text the same way first, about the centre of its
+			//box: the two mirrors cancel on the letters, which read
+			//normally, and the box still ends up where the element's
+			//mirror puts it.
+		const QRectF box(QPointF(0, 0), text_document.size());
+		const QPointF centre = text_transform.mapRect(box).center();
+		painter.setTransform(QTransform::fromTranslate(-centre.x(), -centre.y())
+							 * m_build_mirror
+							 * QTransform::fromTranslate(centre.x(), centre.y()));
+	}
+	painter.setTransform(text_transform, true);
 
 		// force the palette used to render the QTextDocument
 	QAbstractTextDocumentLayout::PaintContext ctx;
diff --git a/sources/factory/elementpicturefactory.h b/sources/factory/elementpicturefactory.h
index d1f2c307a..298442c3e 100644
--- a/sources/factory/elementpicturefactory.h
+++ b/sources/factory/elementpicturefactory.h
@@ -21,6 +21,8 @@
 #include <QMutex>
 #include <QSharedPointer>
 #include <QHash>
+#include <QPair>
+#include <QTransform>
 
 class ElementsLocation;
 class QPicture;
@@ -83,6 +85,8 @@ class ElementPictureFactory
 		}
 
 		void getPictures(const ElementsLocation &location, QPicture &picture, QPicture &low_picture);
+		void getMirroredPictures(const ElementsLocation &location, bool horizontal, bool vertical,
+								 QPicture &picture, QPicture &low_picture);
 		QPixmap pixmap(const ElementsLocation &location);
 		ElementPictureFactory::primitives getPrimitives(const ElementsLocation &location);
 		void dropCache(const ElementsLocation &location);
@@ -94,7 +98,8 @@ class ElementPictureFactory
 		~ElementPictureFactory();
 
 		static QUuid cacheKey(const ElementsLocation &location);
-		bool build(const ElementsLocation &location, QPicture *picture=nullptr, QPicture *low_picture=nullptr);
+		bool build(const ElementsLocation &location, QPicture *picture=nullptr, QPicture *low_picture=nullptr,
+				   const QTransform &mirror=QTransform());
 		void parseElement(const QDomElement &dom, QPainter &painter, primitives &prim) const;
 		void parseLine   (const QDomElement &dom, QPainter &painter, primitives &prim) const;
 		void parseRect   (const QDomElement &dom, QPainter &painter, primitives &prim) const;
@@ -108,6 +113,12 @@ class ElementPictureFactory
 		
 		QHash<QUuid, QPicture> m_pictures_H;
 		QHash<QUuid, QPicture> m_low_pictures_H;
+			/// Drawings for mirrored elements, by element and mirror
+			/// (horizontal, vertical, both), see getMirroredPictures()
+		QHash<QPair<QUuid, int>, QPicture> m_mirrored_pictures_H;
+		QHash<QPair<QUuid, int>, QPicture> m_mirrored_low_pictures_H;
+			/// The mirror build() draws for, read by parseText()
+		QTransform m_build_mirror;
 		QHash<QUuid, QPixmap> m_pixmap_H;
 		QHash<QUuid, primitives> m_primitives_H;
 		static ElementPictureFactory* m_factory;
diff --git a/sources/qetdiagrameditor.cpp b/sources/qetdiagrameditor.cpp
index 5e72f57c2..2dee574ba 100644
--- a/sources/qetdiagrameditor.cpp
+++ b/sources/qetdiagrameditor.cpp
@@ -78,6 +78,7 @@
 #include "utils/qetutils.h"
 #include "undocommand/groupitemscommand.h"
 #include "undocommand/alignselectioncommand.h"
+#include "undocommand/mirrorselectioncommand.h"
 #include "undocommand/rotateselectioncommand.h"
 #include "undocommand/rotatetextscommand.h"
 #include "diagram.h"
@@ -982,6 +983,8 @@ void QETDiagramEditor::setUpActions()
 	m_rotate_selection     = m_selection_actions_group.addAction( QET::Icons::TransformRotate,   tr("Pivoter")                   );
 	m_rotate_group_selection = m_selection_actions_group.addAction( QET::Icons::TransformRotate, tr("Pivoter le groupe")         );
 	m_rotate_texts         = m_selection_actions_group.addAction( QET::Icons::ObjectRotateRight, tr("Orienter les textes")       );
+	m_mirror_horizontal    = m_selection_actions_group.addAction( QET::Icons::ImageFlipHorizontal, tr("Miroir horizontal")       );
+	m_mirror_vertical      = m_selection_actions_group.addAction( QET::Icons::ImageFlipVertical,   tr("Miroir vertical")         );
 	m_find_element         = m_selection_actions_group.addAction( QET::Icons::ZoomDraw,          tr("Retrouver dans le panel")   );
 	m_edit_selection       = m_selection_actions_group.addAction( QET::Icons::ElementEdit,       tr("Éditer l'item sélectionné") );
 	m_group_selected_texts = m_selection_actions_group.addAction( QET::Icons::textGroup,         tr("Grouper les textes sélectionnés"));
@@ -992,6 +995,9 @@ void QETDiagramEditor::setUpActions()
 	ShortcutManager::instance().registerAction(m_rotate_selection, "diagrameditor.rotate_selection", tr("Éditeur de schémas"), Qt::Key_Space);
 	ShortcutManager::instance().registerAction(m_rotate_group_selection, "diagrameditor.rotate_group_selection", tr("Éditeur de schémas"), Qt::SHIFT | Qt::Key_Space);
 	ShortcutManager::instance().registerAction(m_rotate_texts, "diagrameditor.rotate_texts", tr("Éditeur de schémas"), Qt::CTRL | Qt::Key_Space);
+		//M and F, the keys of the same two actions in the element editor
+	ShortcutManager::instance().registerAction(m_mirror_horizontal, "diagrameditor.mirror_horizontal", tr("Éditeur de schémas"), Qt::Key_M);
+	ShortcutManager::instance().registerAction(m_mirror_vertical, "diagrameditor.mirror_vertical", tr("Éditeur de schémas"), Qt::Key_F);
 	ShortcutManager::instance().registerAction(m_find_element, "diagrameditor.find_element", tr("Éditeur de schémas"), QKeySequence());
 	ShortcutManager::instance().registerAction(m_group_selected_texts, "diagrameditor.group_selected_texts", tr("Éditeur de schémas"), QKeySequence());
 	ShortcutManager::instance().registerAction(m_edit_selection, "diagrameditor.edit_selection", tr("Éditeur de schémas"), Qt::CTRL | Qt::Key_E);
@@ -1085,12 +1091,16 @@ void QETDiagramEditor::setUpActions()
 	m_rotate_selection->setStatusTip( tr("Pivote les éléments et textes sélectionnés", "status bar tip"));
 	m_rotate_group_selection->setStatusTip( tr("Pivote la sélection comme un groupe autour de son centre, au lieu de chaque élément sur place", "status bar tip"));
 	m_rotate_texts    ->setStatusTip( tr("Pivote les textes sélectionnés à un angle précis", "status bar tip"));
+	m_mirror_horizontal->setStatusTip( tr("Retourne les éléments sélectionnés de gauche à droite", "status bar tip"));
+	m_mirror_vertical ->setStatusTip( tr("Retourne les éléments sélectionnés de haut en bas", "status bar tip"));
 	m_find_element    ->setStatusTip( tr("Retrouve l'élément sélectionné dans le panel", "status bar tip"));
 
 	m_delete_selection    ->setData("delete_selection");
 	m_rotate_selection    ->setData("rotate_selection");
 	m_rotate_group_selection->setData("rotate_group_selection");
 	m_rotate_texts        ->setData("rotate_selected_text");
+	m_mirror_horizontal   ->setData("mirror_horizontal");
+	m_mirror_vertical     ->setData("mirror_vertical");
 	m_find_element        ->setData("find_selected_element");
 	m_edit_selection      ->setData("edit_selected_element");
 	m_group_selected_texts->setData("group_selected_texts");
@@ -2384,6 +2394,16 @@ void QETDiagramEditor::selectionGroupTriggered(QAction *action)
 		if(c->isValid())
 			diagram->undoStack().push(c);
 	}
+	else if (value == "mirror_horizontal" || value == "mirror_vertical")
+	{
+		auto *c = new MirrorSelectionCommand(
+					diagram,
+					value == "mirror_horizontal" ? Qt::Horizontal : Qt::Vertical);
+		if (c->isValid())
+			diagram->undoStack().push(c);
+		else
+			delete c;
+	}
 	else if (value == "rotate_group_selection")
 	{
 		RotateSelectionCommand *c = new RotateSelectionCommand(diagram, 90, nullptr, true);
@@ -2621,6 +2641,8 @@ void QETDiagramEditor::slot_updateComplexActions()
 			    << m_delete_selection
 			    << m_rotate_selection
 			    << m_rotate_group_selection
+			    << m_mirror_horizontal
+			    << m_mirror_vertical
 			    << m_edit_selection
 			    << m_group_selected_texts
 			    << m_group_selection
@@ -2644,6 +2666,8 @@ void QETDiagramEditor::slot_updateComplexActions()
 	// number of selected elements
 	int selected_elements_count = dc.count(DiagramContent::Elements);
 	m_find_element->setEnabled(selected_elements_count == 1);
+	m_mirror_horizontal->setEnabled(!ro && selected_elements_count);
+	m_mirror_vertical->setEnabled(!ro && selected_elements_count);
 
 	//Actions that need items (elements, conductors, texts...) selected, to be enabled
 	bool copiable_items  = dc.hasCopiableItems();
diff --git a/sources/qetdiagrameditor.h b/sources/qetdiagrameditor.h
index 0cc42c171..ee6292a52 100644
--- a/sources/qetdiagrameditor.h
+++ b/sources/qetdiagrameditor.h
@@ -271,6 +271,8 @@ class QETDiagramEditor : public QETMainWindow
 		*m_rotate_selection,		///< Rotate selected elements and text items by 90 degrees
 		*m_rotate_group_selection = nullptr, ///< Rotate the selection as a whole around its shared center, instead of each item in place
 		*m_rotate_texts,		///< Direct selected text items to a specific angle
+		*m_mirror_horizontal = nullptr, ///< Mirror the selected elements, left and right swap (#1335)
+		*m_mirror_vertical = nullptr,   ///< Mirror the selected elements, top and bottom swap (#1335)
 		*m_find_element,		///< Find the selected element in the panel
 		*m_group_selected_texts = nullptr,
 		*m_group_selection = nullptr,   ///< Group the selected items (#1070)
diff --git a/sources/qetgraphicsitem/crossrefitem.cpp b/sources/qetgraphicsitem/crossrefitem.cpp
index 33b17c463..88184f30d 100644
--- a/sources/qetgraphicsitem/crossrefitem.cpp
+++ b/sources/qetgraphicsitem/crossrefitem.cpp
@@ -124,6 +124,7 @@ void CrossRefItem::setUpConnection()
 		m_update_connection << connect(m_element, &Element::xChanged, this, &CrossRefItem::autoPos);
 		m_update_connection << connect(m_element, &Element::yChanged, this, &CrossRefItem::autoPos);
 		m_update_connection << connect(m_element, &Element::rotationChanged, this, &CrossRefItem::autoPos);
+		m_update_connection << connect(m_element, &Element::mirrorChanged, this, &CrossRefItem::autoPos);
 		set=true;
 	}
 	// For PLC masters, always set up connections for update notifications
@@ -288,6 +289,7 @@ void CrossRefItem::updateLabel()
 		QList<QPointF> positions = m_element->plcTablePositions();
 		QPointF pos = positions.isEmpty() ? QPointF(0, 0) : positions.first();
 		setPos(pos);
+		m_element->keepReadable(this);
 
 		// Populate m_hovered_contacts_map using drawAsPlcTable on a
 		// dummy painter (m_update_map=true).
@@ -338,6 +340,7 @@ void CrossRefItem::autoPos()
 		stackAtBottom();
 	else
 		QGIUtility::centerToParentBottom(this);
+	m_element->keepReadable(this);
 }
 
 /**
@@ -409,9 +412,12 @@ void CrossRefItem::stackAtBottom()
 				moved = true;
 			}
 		}
+			//From pos(), not scenePos(): on a mirrored element scenePos()
+			//also holds the mirror that keeps the cross readable
 		if (self.rect.bottom() != bottom)
 			xref->setPos(xref->parentItem()->mapFromScene(
-				xref->scenePos() + QPointF(0, self.rect.bottom() - bottom)));
+				xref->parentItem()->mapToScene(xref->pos())
+				+ QPointF(0, self.rect.bottom() - bottom)));
 		placed << self;
 	}
 }
diff --git a/sources/qetgraphicsitem/element.cpp b/sources/qetgraphicsitem/element.cpp
index b003b1046..755898ee3 100644
--- a/sources/qetgraphicsitem/element.cpp
+++ b/sources/qetgraphicsitem/element.cpp
@@ -36,10 +36,12 @@
 #include "../ui/elementpropertieswidget.h"
 #include "../undocommand/changeelementinformationcommand.h"
 #include "../undocommand/setautonumcontextcommand.h"
+#include "crossrefitem.h"
 #include "dynamicelementtextitem.h"
 #include "elementtextitemgroup.h"
 #include "iostream"
 
+#include <QAbstractTextDocumentLayout>
 #include <QApplication>
 #include <QCollator>
 #include <QScreen>
@@ -161,6 +163,10 @@ Element::Element(
 	connect(this, &Element::rotationChanged, update_docked_conductors);
 	connect(this, &Element::xChanged, update_docked_conductors);
 	connect(this, &Element::yChanged, update_docked_conductors);
+	connect(this, &Element::mirrorChanged, update_docked_conductors);
+		//The mirror is about the element's own axis, so it follows the
+		//rotation, see applyMirrorTransform()
+	connect(this, &Element::rotationChanged, this, &Element::applyMirrorTransform);
 }
 
 /**
@@ -251,6 +257,152 @@ void Element::displayHelpLine(bool b)
 		t->drawHelpLine(b);
 }
 
+/**
+	@brief Element::setHorizontalMirror
+	Mirror this element about its own vertical axis (its left and right
+	swap), or put it back. See setMirror().
+	@param mirror
+*/
+void Element::setHorizontalMirror(bool mirror)
+{
+	setMirror(mirror, m_vertical_mirror);
+}
+
+/**
+	@brief Element::setVerticalMirror
+	Mirror this element about its own horizontal axis (its top and bottom
+	swap), or put it back. See setMirror().
+	@param mirror
+*/
+void Element::setVerticalMirror(bool mirror)
+{
+	setMirror(m_horizontal_mirror, mirror);
+}
+
+/**
+	@brief Element::setMirror
+	The mirrors are about the element's own axes, through its hotspot, and
+	are applied before the rotation: a mirrored element still turns
+	clockwise with "Pivoter", and orientation() keeps its meaning. On the
+	folio, a mirror of a turned element is the other mirror of the element
+	itself, see MirrorSelectionCommand.
+	The texts of the element, its cross reference and the texts drawn in
+	its symbol are moved to their mirrored place but keep reading normally.
+	@param horizontal : the left and right of the element swap
+	@param vertical : the top and bottom of the element swap
+*/
+void Element::setMirror(bool horizontal, bool vertical)
+{
+	if (horizontal == m_horizontal_mirror && vertical == m_vertical_mirror)
+		return;
+
+	m_horizontal_mirror = horizontal;
+	m_vertical_mirror = vertical;
+
+	m_mirrored_picture = QPicture();
+	m_mirrored_low_zoom_picture = QPicture();
+	if (isMirrored())
+		ElementPictureFactory::instance()->getMirroredPictures(
+					m_location,
+					horizontal,
+					vertical,
+					m_mirrored_picture,
+					m_mirrored_low_zoom_picture);
+
+	applyMirrorTransform();
+	keepChildrenReadable();
+	update();
+	emit mirrorChanged();
+}
+
+/**
+	@brief Element::mirrorTransform
+	@return the mirrors of this element, about its own axes
+*/
+QTransform Element::mirrorTransform() const
+{
+	return QTransform::fromScale(m_horizontal_mirror ? -1 : 1,
+								 m_vertical_mirror ? -1 : 1);
+}
+
+/**
+	@brief Element::applyMirrorTransform
+	QGraphicsItem applies transform() after the rotation, so the mirrors of
+	the element's own axes (S, before rotating) are given here as the
+	mirrors about the rotated axes: R . S . R^-1, which is then applied
+	after R.
+*/
+void Element::applyMirrorTransform()
+{
+	if (!isMirrored())
+	{
+		if (!transform().isIdentity())
+			setTransform(QTransform());
+		return;
+	}
+
+		//QTransform's product applies its left operand first
+	setTransform(QTransform().rotate(-rotation())
+				 * mirrorTransform()
+				 * QTransform().rotate(rotation()));
+}
+
+/**
+	@brief Element::keepReadable
+	Keep @p child, a text, a group of texts or a cross reference of this
+	element, reading normally when this element is mirrored.
+	The child is mirrored a second time, the same way, about the centre of
+	its own box: the box keeps its place in the element, so it lands
+	mirrored with the element, but the two mirrors cancel on what is drawn
+	inside it.
+	Does nothing for an item that is not a direct child of this element.
+	@param child
+*/
+void Element::keepReadable(QGraphicsItem *child) const
+{
+	if (!child || child->parentItem() != this)
+		return;
+
+	if (!isMirrored())
+	{
+		if (!child->transform().isIdentity())
+			child->resetTransform();
+		return;
+	}
+
+		//The rotation part of the child's own transformation, which
+		//QGraphicsItem applies before transform()
+	const QPointF origin = child->transformOriginPoint();
+	QTransform rotation;
+	rotation.translate(origin.x(), origin.y());
+	rotation.rotate(child->rotation());
+	rotation.translate(-origin.x(), -origin.y());
+	const QPointF centre = rotation.mapRect(child->boundingRect()).center();
+
+	const QTransform mirror = QTransform::fromTranslate(-centre.x(), -centre.y())
+							  * mirrorTransform()
+							  * QTransform::fromTranslate(centre.x(), centre.y());
+	if (child->transform() != mirror)
+		child->setTransform(mirror);
+}
+
+/**
+	@brief Element::keepChildrenReadable
+	keepReadable() for every text, group of texts and cross reference
+	which is a direct child of this element.
+*/
+void Element::keepChildrenReadable() const
+{
+	const QList<QGraphicsItem *> children = childItems();
+	for (QGraphicsItem *child : children)
+	{
+		if (child->type() == DynamicElementTextItem::Type
+			|| child->type() == CrossRefItem::Type
+			|| dynamic_cast<ElementTextItemGroup *>(child))
+			keepReadable(child);
+	}
+}
+
 /**
 	@brief Element::paint
 	@param painter
@@ -275,13 +427,16 @@ void Element::paint(
 	QBrush brush;
 	painter->setPen(pen);
 	painter->setBrush(brush);
+	const QPicture &picture = isMirrored() ? m_mirrored_picture : m_picture;
+	const QPicture &low_zoom_picture = isMirrored() ? m_mirrored_low_zoom_picture
+												   : m_low_zoom_picture;
 	if (options && options->levelOfDetailFromTransform(painter->worldTransform()) < 0.5)
 	{
-		if (!m_low_zoom_picture.isNull())
-			painter->drawPicture(0, 0, m_low_zoom_picture);
+		if (!low_zoom_picture.isNull())
+			painter->drawPicture(0, 0, low_zoom_picture);
 	} else {
-		if (!m_picture.isNull())
-			painter->drawPicture(0, 0, m_picture);
+		if (!picture.isNull())
+			painter->drawPicture(0, 0, picture);
 	}
 
 	painter->restore(); //Restore the QPainter after use drawPicture
@@ -938,6 +1093,11 @@ bool Element::fromXml(QDomElement &e,
 	for(DynamicElementTextItem *deti : m_dynamic_text_list)
 		deti->m_block_alignment = false;
 
+		//Last, so that the texts and groups loaded above are kept readable
+	const QString mirror = e.attribute(QStringLiteral("mirror"));
+	setMirror(mirror == QLatin1String("horizontal") || mirror == QLatin1String("both"),
+			  mirror == QLatin1String("vertical") || mirror == QLatin1String("both"));
+
 	m_state = QET::GIOK;
 	return(true);
 }
@@ -987,6 +1147,13 @@ QDomElement Element::toXml(
 	element.setAttribute(QStringLiteral("y"), QString::number(pos().y()));
 	element.setAttribute(QStringLiteral("z"), QString::number(this->zValue()));
 	element.setAttribute(QStringLiteral("orientation"), QString::number(orientation()));
+		//Written only when set, so a project without a mirrored element
+		//saves exactly as before
+	if (isMirrored())
+		element.setAttribute(QStringLiteral("mirror"),
+							 !m_vertical_mirror ? QStringLiteral("horizontal")
+							 : !m_horizontal_mirror ? QStringLiteral("vertical")
+							 : QStringLiteral("both"));
 	element.setAttribute(QStringLiteral("is_movable"), bool(is_movable_));
 
 	/* get the first id to use for the bounds of this element
@@ -1133,18 +1300,25 @@ QDomElement Element::toXml(
 */
 void Element::addDynamicTextItem(DynamicElementTextItem *deti)
 {
-	if (deti && !m_dynamic_text_list.contains(deti))
-	{
-		m_dynamic_text_list.append(deti);
-		deti->setParentItem(this);
-		emit textAdded(deti);
-	}
+	if (!deti || m_dynamic_text_list.contains(deti))
+		deti = new DynamicElementTextItem(this);
 	else
-	{
-		DynamicElementTextItem *text = new DynamicElementTextItem(this);
-		m_dynamic_text_list.append(text);
-		emit textAdded(text);
-	}
+		deti->setParentItem(this);
+
+	m_dynamic_text_list.append(deti);
+
+		//On a mirrored element, the mirror of the text depends on the size
+		//and the rotation of the text, see keepReadable()
+	connect(deti->document()->documentLayout(),
+			&QAbstractTextDocumentLayout::documentSizeChanged,
+			this, [this, deti]() {keepReadable(deti);});
+	connect(deti, &DynamicElementTextItem::rotationChanged,
+			this, [this, deti]() {keepReadable(deti);});
+	connect(deti, &DynamicElementTextItem::rotationPointCenterChanged,
+			this, [this, deti]() {keepReadable(deti);});
+	keepReadable(deti);
+
+	emit textAdded(deti);
 }
 
 /**
@@ -1156,10 +1330,18 @@ void Element::addDynamicTextItem(DynamicElementTextItem *deti)
 */
 void Element::removeDynamicTextItem(DynamicElementTextItem *deti)
 {
+		//Undo the connections and the mirror of addDynamicTextItem()
+	auto forget = [this, deti]() {
+		disconnect(deti->document()->documentLayout(), nullptr, this, nullptr);
+		disconnect(deti, nullptr, this, nullptr);
+		deti->resetTransform();
+	};
+
 	if (m_dynamic_text_list.contains(deti))
 	{
 		m_dynamic_text_list.removeOne(deti);
 		deti->setParentItem(nullptr);
+		forget();
 		emit textRemoved(deti);
 		return;
 	}
@@ -1171,6 +1353,7 @@ void Element::removeDynamicTextItem(DynamicElementTextItem *deti)
 			removeTextFromGroup(deti, group);
 			m_dynamic_text_list.removeOne(deti);
 			deti->setParentItem(nullptr);
+			forget();
 			emit textRemoved(deti);
 			return;
 		}
@@ -2003,6 +2186,13 @@ Element::ReloadPictureResult Element::reloadPicture()
 
 	m_picture = picture;
 	m_low_zoom_picture = low_zoom_picture;
+	if (isMirrored())
+		ElementPictureFactory::instance()->getMirroredPictures(
+					m_location,
+					m_horizontal_mirror,
+					m_vertical_mirror,
+					m_mirrored_picture,
+					m_mirrored_low_zoom_picture);
 	update();
 	return ReloadPictureResult::Reloaded;
 }
diff --git a/sources/qetgraphicsitem/element.h b/sources/qetgraphicsitem/element.h
index f4c82853f..e5b3d2295 100644
--- a/sources/qetgraphicsitem/element.h
+++ b/sources/qetgraphicsitem/element.h
@@ -46,6 +46,9 @@ class Element : public QetGraphicsItem
 	friend class DynamicElementTextItem;
 
 	Q_OBJECT
+	Q_PROPERTY(bool horizontalMirror READ hasHorizontalMirror WRITE setHorizontalMirror NOTIFY mirrorChanged)
+	Q_PROPERTY(bool verticalMirror READ hasVerticalMirror WRITE setVerticalMirror NOTIFY mirrorChanged)
+
 	public:
 			/**
 				@brief The kind enum
@@ -111,6 +114,7 @@ class Element : public QetGraphicsItem
 		void textRemovedFromGroup(
 				DynamicElementTextItem *text,
 				ElementTextItemGroup *group);
+		void mirrorChanged();
 
 	public slots:
 		void updateConductorTexts();
@@ -185,6 +189,13 @@ class Element : public QetGraphicsItem
 				int> &) const;
 		QUuid uuid() const;
 		int orientation() const;
+		bool hasHorizontalMirror() const {return m_horizontal_mirror;}
+		bool hasVerticalMirror() const {return m_vertical_mirror;}
+		bool isMirrored() const {return m_horizontal_mirror || m_vertical_mirror;}
+		void setHorizontalMirror(bool mirror);
+		void setVerticalMirror(bool mirror);
+		QTransform mirrorTransform() const;
+		void keepReadable(QGraphicsItem *child) const;
 
 			//METHODS related to texts
 		void addDynamicTextItem(DynamicElementTextItem *deti = nullptr);
@@ -296,10 +307,15 @@ class Element : public QetGraphicsItem
 	QList <Terminal *> m_terminals;
 	QPicture m_picture;
 	QPicture m_low_zoom_picture;
+	QPicture m_mirrored_picture;
+	QPicture m_mirrored_low_zoom_picture;
 	ElementData m_data;
 	QList<QPointF> m_plc_table_positions;  // Positions of plc_table parts in the element definition
 
 	void drawPlcTable(QPainter *painter);
+	void setMirror(bool horizontal, bool vertical);
+	void applyMirrorTransform();
+	void keepChildrenReadable() const;
 
 	public:
 		/// Positions where the PLC IO table is drawn (from the .elmt file).
@@ -310,6 +326,8 @@ class Element : public QetGraphicsItem
 		QSize   dimensions;
 		QPoint  hotspot_coord;
 		bool m_mouse_over = false;
+		bool m_horizontal_mirror = false;
+		bool m_vertical_mirror = false;
 		QString m_prefix;
 		QList <DynamicElementTextItem *> m_dynamic_text_list;
 		QList <ElementTextItemGroup *> m_texts_group;
diff --git a/sources/qetgraphicsitem/elementtextitemgroup.cpp b/sources/qetgraphicsitem/elementtextitemgroup.cpp
index 86f6cd054..a14a5ef0c 100644
--- a/sources/qetgraphicsitem/elementtextitemgroup.cpp
+++ b/sources/qetgraphicsitem/elementtextitemgroup.cpp
@@ -119,6 +119,12 @@ void ElementTextItemGroup::addToGroup(QGraphicsItem *item)
 		if((item->rotation() != rotation()) && !m_block_alignment_update)
 			item->setRotation(rotation());
 		
+			//On a mirrored element, QGraphicsItemGroup::addToGroup() would
+			//fold the mirror that keeps the text and this group readable
+			//(Element::keepReadable()) into the text's transform. The group
+			//gets its own back from updateAlignment().
+		item->resetTransform();
+		resetTransform();
 		QGraphicsItemGroup::addToGroup(item);
 		updateAlignment();
 		
@@ -153,6 +159,7 @@ void ElementTextItemGroup::addToGroup(QGraphicsItem *item)
 */
 void ElementTextItemGroup::removeFromGroup(QGraphicsItem *item)
 {
+	resetTransform(); //See addToGroup(), given back by updateAlignment()
 	QGraphicsItemGroup::removeFromGroup(item);
 	//the item transformation is not reset, we must do it ourselves,
 	// because for example if the group rotation is 45°
@@ -162,6 +169,8 @@ void ElementTextItemGroup::removeFromGroup(QGraphicsItem *item)
 	item->resetTransform();
 	item->setRotation(this->rotation());
 	item->setFlag(QGraphicsItem::ItemIsSelectable, true);
+	if (m_parent_element)
+		m_parent_element->keepReadable(item);
 	updateAlignment();
 	
 	if(DynamicElementTextItem *deti = qgraphicsitem_cast<DynamicElementTextItem *>(item))
@@ -232,6 +241,10 @@ void ElementTextItemGroup::updateAlignment()
 	prepareGeometryChange();
 	
 	QList <DynamicElementTextItem *> texts = this->texts();
+
+		//The mirror of a mirrored element's group depends on the size of
+		//the group: drop it while the texts are laid out, set it back after
+	resetTransform();
 	
 	qreal rotation_ = rotation();
 	
@@ -302,6 +315,8 @@ void ElementTextItemGroup::updateAlignment()
 	
 		//Restore the rotation
 	setRotation(rotation_);
+	if (m_parent_element)
+		m_parent_element->keepReadable(this);
 	
 	if(m_Xref_item)
 		m_Xref_item->autoPos();
@@ -357,6 +372,7 @@ void ElementTextItemGroup::setHoldToBottomPage(bool hold)
 		setFlag(QGraphicsItem::ItemIsMovable, false);
 		connect(m_parent_element, &Element::yChanged, this, &ElementTextItemGroup::autoPos);
 		connect(m_parent_element, &Element::rotationChanged, this, &ElementTextItemGroup::autoPos);
+		connect(m_parent_element, &Element::mirrorChanged, this, &ElementTextItemGroup::autoPos);
 		if(m_parent_element->linkType() == Element::Master)
 		{
 			//We use timer to let the time of the parent element
@@ -396,6 +412,8 @@ void ElementTextItemGroup::setHoldToBottomPage(bool hold)
 			   this, &ElementTextItemGroup::autoPos);
 		disconnect(m_parent_element, &Element::rotationChanged,
 			   this, &ElementTextItemGroup::autoPos);
+		disconnect(m_parent_element, &Element::mirrorChanged,
+			   this, &ElementTextItemGroup::autoPos);
 		if(m_parent_element->linkType() == Element::Master)
 		{
 			disconnect(m_linked_changed_timer);
@@ -630,6 +648,10 @@ QRectF ElementTextItemGroup::boundingRect() const
 void ElementTextItemGroup::setRotation(qreal angle)
 {	
 	QGraphicsItemGroup::setRotation(angle);
+		//On a mirrored element, the mirror that keeps this group readable
+		//is about the centre of its turned box
+	if (m_parent_element)
+		m_parent_element->keepReadable(this);
 	emit rotationChanged(angle);
 }
 
diff --git a/sources/qetgraphicsitem/qgraphicsitemutility.cpp b/sources/qetgraphicsitem/qgraphicsitemutility.cpp
index 85da0396e..34fdf3ecf 100644
--- a/sources/qetgraphicsitem/qgraphicsitemutility.cpp
+++ b/sources/qetgraphicsitem/qgraphicsitemutility.cpp
@@ -75,6 +75,9 @@ bool centerToBottomDiagram (QGraphicsItem *item_to_center, Element *element_to_f
 	
 	item_to_center -> setPos(0,0);	  //Due to a weird behavior or bug, before setting the new position and rotation,
 	item_to_center -> setRotation(0); //we must set the position and rotation to 0.
+		//Same for the mirror that keeps it readable on a mirrored element,
+		//given back below
+	item_to_center -> resetTransform();
 	
 	item_to_center->setPos(item_to_center->mapFromScene(point));
 	
@@ -87,6 +90,23 @@ bool centerToBottomDiagram (QGraphicsItem *item_to_center, Element *element_to_f
 	if(rot != 0) {
 		item_to_center->setRotation(item_to_center->rotation() - rot);
 	}
+	element_to_follow->keepReadable(item_to_center);
+
+		//On a mirrored element the item's box extends from its pos() the
+		//mirrored way, so it is not where the lines above meant. Put it
+		//there: centred on the element, its top at the same height.
+	if (element_to_follow->isMirrored() && item_to_center->parentItem())
+	{
+		const QRectF placed = item_to_center->sceneBoundingRect();
+		const QPointF wanted(
+					element_to_follow->sceneBoundingRect().center().x()
+					- placed.width() / 2,
+					border.bottom() - item_to_center->boundingRect().height() - offset);
+		QGraphicsItem *parent = item_to_center->parentItem();
+		item_to_center->setPos(parent->mapFromScene(
+								   parent->mapToScene(item_to_center->pos())
+								   + wanted - placed.topLeft()));
+	}
 
 	return true;
 }
diff --git a/sources/qetgraphicsitem/terminal.cpp b/sources/qetgraphicsitem/terminal.cpp
index e9e114a05..3a8564ab3 100644
--- a/sources/qetgraphicsitem/terminal.cpp
+++ b/sources/qetgraphicsitem/terminal.cpp
@@ -118,13 +118,20 @@ Qet::Orientation Terminal::orientation() const
 		// orientations actuelle et par defaut de l'element
 		// current and default element orientations
 		int ori_cur = elt -> orientation();
-	if (ori_cur == 0) return(d->m_orientation);
+		// The mirrors of an element are about its own axes, before it is
+		// rotated (Element::setMirror()): a horizontal one swaps east and
+		// west, a vertical one north and south
+		Qet::Orientation ori_elmt = d->m_orientation;
+		if (Qet::isHorizontal(ori_elmt) ? elt -> hasHorizontalMirror()
+										: elt -> hasVerticalMirror())
+			ori_elmt = (Qet::Orientation)((ori_elmt + 2) % 4);
+	if (ori_cur == 0) return(ori_elmt);
 		else {
 			// calcul l'angle de rotation implique par l'orientation de l'element parent
 			// angle de rotation de la borne sur la scene, divise par 90
 			// calculates the angle of rotation implied by the orientation of the parent
 			// element angle of rotation of the terminal on the scene, divided by 90
-			int angle = ori_cur + d->m_orientation;
+			int angle = ori_cur + ori_elmt;
 			while (angle >= 4) angle -= 4;
 			return((Qet::Orientation)angle);
 		}
@@ -299,6 +306,23 @@ void Terminal::paint(
 		QFontMetrics fm(d->m_label_font);
 		QSizeF text_size = fm.size(Qt::TextSingleLine, display_name);
 
+			// On a mirrored element, mirror the name a second time about
+			// the centre of its box, in the frame it is drawn in (turned
+			// by label_rotation): its box stays where the element's mirror
+			// puts it, but it reads normally (Element::keepReadable())
+		const Element *mirrored = qgraphicsitem_cast<Element *>(parentItem());
+		if (mirrored && !mirrored->isMirrored()) mirrored = nullptr;
+		auto keep_readable = [painter, mirrored](const QRectF &rect, qreal label_rotation) {
+			if (!mirrored) return;
+			const QTransform mirror = QTransform().rotate(label_rotation)
+									  * mirrored->mirrorTransform()
+									  * QTransform().rotate(-label_rotation);
+			const QPointF c = rect.center();
+			painter->setTransform(QTransform::fromTranslate(-c.x(), -c.y())
+								  * mirror
+								  * QTransform::fromTranslate(c.x(), c.y()), true);
+		};
+
 		if (!qFuzzyIsNull(d->m_label_rotation)) {
 			painter->save();
 			painter->translate(label_pos);
@@ -314,6 +338,7 @@ void Terminal::paint(
 			else if (d->m_label_valignment & Qt::AlignBottom) ry = -text_size.height();
 
 			QRectF text_rect(QPointF(rx, ry), text_size);
+			keep_readable(text_rect, d->m_label_rotation);
 			painter->drawText(text_rect, static_cast<int>(d->m_label_halignment | d->m_label_valignment), display_name);
 			painter->restore();
 		} else {
@@ -327,6 +352,7 @@ void Terminal::paint(
 			else if (d->m_label_valignment & Qt::AlignBottom) dy = -text_size.height();
 
 			QRectF text_rect(label_pos + QPointF(dx, dy), text_size);
+			keep_readable(text_rect, 0);
 			if (d->m_label_frame) {
 				painter->drawRect(text_rect.adjusted(-1, -1, 1, 1));
 			}
diff --git a/sources/scripting/liveserver.cpp b/sources/scripting/liveserver.cpp
index f76aaaaec..a2da5bbe7 100644
--- a/sources/scripting/liveserver.cpp
+++ b/sources/scripting/liveserver.cpp
@@ -550,6 +550,8 @@ QStringList LiveServer::allowedCommands()
 		QStringLiteral("diagrameditor.zoom_fit"),
 		QStringLiteral("diagrameditor.zoom_reset"),
 		QStringLiteral("diagrameditor.rotate_selection"),
+		QStringLiteral("diagrameditor.mirror_horizontal"),
+		QStringLiteral("diagrameditor.mirror_vertical"),
 		QStringLiteral("diagrameditor.rotate_texts"),
 		QStringLiteral("diagrameditor.snap_selection_to_grid"),
 		QStringLiteral("diagrameditor.group_selection"),
diff --git a/sources/scripting/qetscriptapi.cpp b/sources/scripting/qetscriptapi.cpp
index 3ddbb537a..d5c69ea89 100644
--- a/sources/scripting/qetscriptapi.cpp
+++ b/sources/scripting/qetscriptapi.cpp
@@ -61,6 +61,7 @@
 #include "../qetgraphicsitem/dynamicelementtextitem.h"
 #include "../qetgraphicsitem/independenttextitem.h"
 #include "../qetgraphicsitem/qetshapeitem.h"
+#include "../undocommand/mirrorselectioncommand.h"
 #include "../undocommand/promoteshapecommand.h"
 #include "../TerminalStrip/UndoCommand/addterminalstripcommand.h"
 #include "../TerminalStrip/UndoCommand/addterminaltostripcommand.h"
@@ -833,6 +834,43 @@ bool QetScriptApi::rotateElement(int folioIndex, const QString &elementUuid, dou
 	return true;
 }
 
+/**
+	@brief QetScriptApi::mirrorElement
+	Mirror an element in place, as "Miroir horizontal" (left and right
+	swap) or, with @p vertical, "Miroir vertical" (top and bottom swap)
+	do on a selection. Mirroring twice the same way puts it back.
+	@return false if the element is not found or the project is read only
+*/
+bool QetScriptApi::mirrorElement(int folioIndex, const QString &elementUuid, bool vertical)
+{
+	if (m_project && m_project->isReadOnly()) {
+		log(QStringLiteral("qet.mirrorElement: project is read-only"));
+		return false;
+	}
+	Element *element = findElement(folioIndex, elementUuid);
+	if (!element) return false;
+
+	m_project->undoStack()->push(new MirrorSelectionCommand(
+		{element}, vertical ? Qt::Vertical : Qt::Horizontal));
+	return true;
+}
+
+/**
+	@brief QetScriptApi::elementMirror
+	@return the mirrors of the element about its own axes, as saved in the
+	project (Element::setMirror()): "horizontal", "vertical", "both", or ""
+	if it is not mirrored or not found. On a turned element, a horizontal
+	mirror of the folio is a vertical mirror of the element.
+*/
+QString QetScriptApi::elementMirror(int folioIndex, const QString &elementUuid) const
+{
+	const Element *element = findElement(folioIndex, elementUuid);
+	if (!element || !element->isMirrored()) return QString();
+	if (!element->hasVerticalMirror()) return QStringLiteral("horizontal");
+	if (!element->hasHorizontalMirror()) return QStringLiteral("vertical");
+	return QStringLiteral("both");
+}
+
 QStringList QetScriptApi::elementUuids(int folioIndex) const
 {
 	QStringList uuids;
diff --git a/sources/scripting/qetscriptapi.h b/sources/scripting/qetscriptapi.h
index be9bdf061..b6baa85b7 100644
--- a/sources/scripting/qetscriptapi.h
+++ b/sources/scripting/qetscriptapi.h
@@ -398,6 +398,8 @@ class QetScriptApi : public QObject
 		Q_INVOKABLE bool setElementPosition(int folioIndex, const QString &elementUuid, double x, double y);
 		Q_INVOKABLE bool moveElement(int folioIndex, const QString &elementUuid, double dx, double dy);
 		Q_INVOKABLE bool rotateElement(int folioIndex, const QString &elementUuid, double angle);
+		Q_INVOKABLE bool mirrorElement(int folioIndex, const QString &elementUuid, bool vertical = false);
+		Q_INVOKABLE QString elementMirror(int folioIndex, const QString &elementUuid) const;
 		Q_INVOKABLE bool deleteElement(int folioIndex, const QString &elementUuid);
 
 		// -- address what is already there --
diff --git a/sources/undocommand/mirrorselectioncommand.cpp b/sources/undocommand/mirrorselectioncommand.cpp
new file mode 100644
index 000000000..01c5783a5
--- /dev/null
+++ b/sources/undocommand/mirrorselectioncommand.cpp
@@ -0,0 +1,125 @@
+/*
+	Copyright 2006-2026 The QElectroTech Team
+	This file is part of QElectroTech.
+	
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+	
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+	
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "mirrorselectioncommand.h"
+
+#include "../QPropertyUndoCommand/qpropertyundocommand.h"
+#include "../diagram.h"
+#include "../qetgraphicsitem/element.h"
+
+/**
+	@brief MirrorSelectionCommand::MirrorSelectionCommand
+	Mirror the elements selected in @p diagram; the other selected items
+	are left as they are. See the other constructor.
+	@param diagram : the diagram whose selection is mirrored
+	@param orientation : Qt::Horizontal swaps left and right,
+	Qt::Vertical swaps top and bottom
+	@param parent : parent undo command
+*/
+MirrorSelectionCommand::MirrorSelectionCommand(Diagram *diagram,
+											   Qt::Orientation orientation,
+											   QUndoCommand *parent) :
+	MirrorSelectionCommand(selectedElements(diagram), orientation, parent)
+{}
+
+/**
+	@brief MirrorSelectionCommand::MirrorSelectionCommand
+	The mirrors of an element are about its own axes, before it is rotated
+	(Element::setMirror()). Turned by 0 or 180 degrees, the element's axes
+	are the folio's, so a horizontal mirror on the folio is the element's
+	own horizontal mirror; turned by 90 or 270 degrees, they are swapped,
+	so it is the element's vertical mirror. The rotation never changes.
+	Each element is mirrored in place: its centre stays where it was.
+	@param elements : the elements to mirror
+	@param orientation : Qt::Horizontal swaps left and right on the folio,
+	Qt::Vertical swaps top and bottom
+	@param parent : parent undo command
+*/
+MirrorSelectionCommand::MirrorSelectionCommand(const QList<Element *> &elements,
+											   Qt::Orientation orientation,
+											   QUndoCommand *parent) :
+	QUndoCommand(parent)
+{
+	setText(orientation == Qt::Horizontal
+			? QObject::tr("Miroir horizontal")
+			: QObject::tr("Miroir vertical"));
+
+	for (Element *element : elements)
+	{
+		if (!element)
+			continue;
+
+		const bool turned = element->orientation() % 2;
+		const bool horizontal = (orientation == Qt::Horizontal) != turned;
+
+		bool new_horizontal = element->hasHorizontalMirror();
+		bool new_vertical = element->hasVerticalMirror();
+		if (horizontal)
+		{
+			new_horizontal = !new_horizontal;
+			new QPropertyUndoCommand(element, "horizontalMirror",
+									 !new_horizontal, new_horizontal, this);
+		}
+		else
+		{
+			new_vertical = !new_vertical;
+			new QPropertyUndoCommand(element, "verticalMirror",
+									 !new_vertical, new_vertical, this);
+		}
+
+			//The mirror is about the element's hotspot, which is often a
+			//corner of the symbol: move it so that it stays where it was,
+			//centre on centre, and on the grid
+		QPointF centre = element->boundingRect().center();
+		centre = QTransform::fromScale(new_horizontal ? -1 : 1, new_vertical ? -1 : 1)
+				 .map(centre);
+		centre = QTransform().rotate(element->rotation()).map(centre);
+
+		const QPointF old_pos = element->pos();
+		const QPointF new_pos = Diagram::snapToGrid(
+					element->mapToScene(element->boundingRect().center()) - centre);
+		if (new_pos != old_pos)
+			new QPropertyUndoCommand(element, "pos", old_pos, new_pos, this);
+	}
+}
+
+/**
+	@brief MirrorSelectionCommand::selectedElements
+	@param diagram
+	@return the elements selected in @p diagram, none if it is read only
+*/
+QList<Element *> MirrorSelectionCommand::selectedElements(const Diagram *diagram)
+{
+	QList<Element *> elements;
+	if (!diagram || diagram->isReadOnly())
+		return elements;
+
+	const QList<QGraphicsItem *> items = diagram->selectedItems();
+	for (QGraphicsItem *item : items)
+		if (Element *element = qgraphicsitem_cast<Element *>(item))
+			elements << element;
+	return elements;
+}
+
+/**
+	@brief MirrorSelectionCommand::isValid
+	@return true if at least one element is mirrored by this command
+*/
+bool MirrorSelectionCommand::isValid() const
+{
+	return childCount() > 0;
+}
diff --git a/sources/undocommand/mirrorselectioncommand.h b/sources/undocommand/mirrorselectioncommand.h
new file mode 100644
index 000000000..b2f3a13b5
--- /dev/null
+++ b/sources/undocommand/mirrorselectioncommand.h
@@ -0,0 +1,48 @@
+/*
+	Copyright 2006-2026 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#ifndef MIRRORSELECTIONCOMMAND_H
+#define MIRRORSELECTIONCOMMAND_H
+
+#include <QList>
+#include <QUndoCommand>
+
+class Diagram;
+class Element;
+
+/**
+	@brief The MirrorSelectionCommand class
+	Mirror elements in place, horizontally (left and right swap) or
+	vertically (top and bottom swap), on the folio. See Element::setMirror()
+*/
+class MirrorSelectionCommand : public QUndoCommand
+{
+	public:
+		MirrorSelectionCommand(Diagram *diagram,
+							   Qt::Orientation orientation,
+							   QUndoCommand *parent = nullptr);
+		MirrorSelectionCommand(const QList<Element *> &elements,
+							   Qt::Orientation orientation,
+							   QUndoCommand *parent = nullptr);
+
+		bool isValid() const;
+
+	private:
+		static QList<Element *> selectedElements(const Diagram *diagram);
+};
+
+#endif // MIRRORSELECTIONCOMMAND_H
diff --git a/tests/qttest/CMakeLists.txt b/tests/qttest/CMakeLists.txt
index 502887209..e02e9e26e 100644
--- a/tests/qttest/CMakeLists.txt
+++ b/tests/qttest/CMakeLists.txt
@@ -775,6 +775,19 @@ if(QET_HAS_SCRIPTING)
     "QET_TEST_BINARY_PATH=\"$<TARGET_FILE:qelectrotech>\""
     "QET_EXAMPLES_DIR=\"${QET_DIR}/examples\"")
 
+  # Mirroring a symbol on its folio (#1335): its terminals swap sides and
+  # face the other way, a second mirror puts it back, and the mirror is
+  # kept by a save. Through the real binary's --run on perceuse.qet.
+  add_executable(
+    tst_scriptmirror
+    tst_scriptmirror.cpp)
+  add_test(NAME tst_scriptmirror COMMAND tst_scriptmirror)
+  add_dependencies(tst_scriptmirror qelectrotech)
+  target_link_libraries(tst_scriptmirror PRIVATE Qt::Test Qt::Xml)
+  target_compile_definitions(tst_scriptmirror PRIVATE
+    "QET_TEST_BINARY_PATH=\"$<TARGET_FILE:qelectrotech>\""
+    "QET_EXAMPLES_DIR=\"${QET_DIR}/examples\"")
+
   # Undoing a crop of a picture restores its crop rectangle too, so a
   # project saved after the undo does not record the undone crop.
   add_executable(
diff --git a/tests/qttest/tst_scriptmirror.cpp b/tests/qttest/tst_scriptmirror.cpp
new file mode 100644
index 000000000..338b5e19d
--- /dev/null
+++ b/tests/qttest/tst_scriptmirror.cpp
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <QtTest>
+
+#include <QDomDocument>
+#include <QFile>
+#include <QJsonArray>
+#include <QJsonDocument>
+#include <QJsonObject>
+#include <QProcess>
+#include <QProcessEnvironment>
+#include <QTemporaryDir>
+
+// Mirroring a symbol on its folio (#1335), through the real binary's --run
+// on perceuse.qet: qet.mirrorElement() pushes the same undo command as
+// Edit > Miroir horizontal / vertical. A horizontal mirror swaps the
+// terminals left and right and turns the ones facing east to face west; a
+// vertical one does the same top and bottom; mirroring twice the same way
+// puts the symbol back exactly; and a save keeps the mirror.
+class tst_scriptmirror : public QObject
+{
+	Q_OBJECT
+
+	QTemporaryDir m_dir;
+
+	// Run @p script on @p project in a sandbox of its own and return the
+	// JSON object it logged.
+	QJsonObject run(const QString &script, const QString &project)
+	{
+		const QString path = m_dir.filePath(QStringLiteral("probe.js"));
+		const QString home = m_dir.filePath(QStringLiteral("home"));
+		QDir().mkpath(home);
+		QFile f(path);
+		if (!f.open(QIODevice::WriteOnly)) return {};
+		f.write(script.toUtf8());
+		f.close();
+
+		QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+		env.insert(QStringLiteral("QT_QPA_PLATFORM"), QStringLiteral("offscreen"));
+		env.insert(QStringLiteral("QET_ENABLE_SCRIPTING"), QStringLiteral("1"));
+		env.insert(QStringLiteral("HOME"), home);
+		env.insert(QStringLiteral("XDG_CONFIG_HOME"), home + QStringLiteral("/config"));
+		env.insert(QStringLiteral("XDG_DATA_HOME"), home + QStringLiteral("/data"));
+		env.insert(QStringLiteral("TMPDIR"), m_dir.path());
+		QProcess proc;
+		proc.setProcessEnvironment(env);
+		proc.start(QStringLiteral(QET_TEST_BINARY_PATH),
+				   {QStringLiteral("--run"), path, project});
+		if (!proc.waitForFinished(120000)) return {};
+		const QString out = QString::fromUtf8(proc.readAllStandardOutput()
+											  + proc.readAllStandardError());
+		const QString mark = QStringLiteral("PROBE ");
+		for (const QString &line : out.split(QLatin1Char('\n'))) {
+			const int i = line.indexOf(mark);
+			if (i >= 0)
+				return QJsonDocument::fromJson(line.mid(i + mark.size()).toUtf8()).object();
+		}
+		return {};
+	}
+
+	static QString facing(const QJsonArray &terminals, int i)
+	{
+		return terminals.at(i).toObject().value(QStringLiteral("facing")).toString();
+	}
+	static double coord(const QJsonArray &terminals, int i, const char *axis)
+	{
+		return terminals.at(i).toObject().value(QLatin1String(axis)).toDouble();
+	}
+
+	// The facing of a terminal once mirrored: across a vertical line
+	// (horizontal mirror) east and west swap, across a horizontal one north
+	// and south do.
+	static QString mirrored(const QString &facing, bool vertical)
+	{
+		const QString swap = vertical ? QStringLiteral("ns") : QStringLiteral("ew");
+		const int i = swap.indexOf(facing);
+		return i < 0 ? facing : QString(swap.at(1 - i));
+	}
+
+	// @p after is @p before mirrored horizontally (or vertically): the
+	// terminals face the mirrored way, keep the other coordinate, and are
+	// mirrored across one same line, so x + x' (or y + y') is the same for
+	// all of them.
+	static void checkMirrored(const QJsonArray &before, const QJsonArray &after, bool vertical)
+	{
+		QCOMPARE(after.size(), before.size());
+		const char *across = vertical ? "y" : "x";
+		const char *along  = vertical ? "x" : "y";
+		const double axis = coord(before, 0, across) + coord(after, 0, across);
+		const double shift = coord(after, 0, along) - coord(before, 0, along);
+		for (int i = 0; i < before.size(); ++i) {
+			QCOMPARE(facing(after, i), mirrored(facing(before, i), vertical));
+			QCOMPARE(coord(before, i, across) + coord(after, i, across), axis);
+			QCOMPARE(coord(after, i, along) - coord(before, i, along), shift);
+		}
+	}
+
+	static QString script(const QString &body)
+	{
+		return QStringLiteral(
+			"function terms(f, el) {\n"
+			"  var r = [], n = qet.elementTerminals(f, el).length;\n"
+			"  for (var i = 0; i < n; i++) r.push(qet.terminalPosition(f, el, i));\n"
+			"  return r;\n"
+			"}\n") + body;
+	}
+
+private slots:
+	void initTestCase()
+	{
+		QVERIFY(m_dir.isValid());
+		QVERIFY(QFile::exists(QStringLiteral(QET_TEST_BINARY_PATH)));
+	}
+
+	void mirrorBackAndSave()
+	{
+		const QString saved = m_dir.filePath(QStringLiteral("mirrored.qet"));
+		const QJsonObject r = run(script(QStringLiteral(
+			// a symbol with terminals at different x and different y, one
+			// of them facing east or west
+			"var pick = null;\n"
+			"for (var f = 0; f < qet.folioCount() && !pick; f++) {\n"
+			"  var els = qet.elementUuids(f);\n"
+			"  for (var e = 0; e < els.length && !pick; e++) {\n"
+			"    var t = terms(f, els[e]);\n"
+			"    if (t.length < 2) continue;\n"
+			"    var side = t.some(function (p) { return p.facing === 'e' || p.facing === 'w'; });\n"
+			"    var xs = t.some(function (p) { return p.x !== t[0].x; });\n"
+			"    var ys = t.some(function (p) { return p.y !== t[0].y; });\n"
+			"    if (side && xs && ys) pick = {f: f, e: els[e]};\n"
+			"  }\n"
+			"}\n"
+			"var f = pick.f, el = pick.e, out = {element: el};\n"
+			"out.before = terms(f, el);\n"
+			"qet.mirrorElement(f, el, false);\n"
+			"out.h = terms(f, el); out.hMirror = qet.elementMirror(f, el);\n"
+			"qet.mirrorElement(f, el, false);\n"
+			"out.back = terms(f, el); out.backMirror = qet.elementMirror(f, el);\n"
+			"qet.mirrorElement(f, el, true);\n"
+			"out.v = terms(f, el); out.vMirror = qet.elementMirror(f, el);\n"
+			"qet.undo();\n"
+			"out.undone = terms(f, el);\n"
+			"qet.mirrorElement(f, el, true);\n"
+			"out.folio = f;\n"
+			"out.saved = qet.save(%1);\n"
+			"qet.log('PROBE ' + JSON.stringify(out));\n")
+			.arg(QString::fromUtf8(QJsonDocument(QJsonArray{saved}).toJson(QJsonDocument::Compact)).mid(1).chopped(1))),
+			QStringLiteral(QET_EXAMPLES_DIR "/perceuse.qet"));
+
+		QVERIFY2(!r.isEmpty(), "the script logged nothing");
+		const QJsonArray before = r.value(QStringLiteral("before")).toArray();
+		QVERIFY(before.size() >= 2);
+
+		QVERIFY(!r.value(QStringLiteral("hMirror")).toString().isEmpty());
+		checkMirrored(before, r.value(QStringLiteral("h")).toArray(), false);
+
+		QCOMPARE(r.value(QStringLiteral("backMirror")).toString(), QString());
+		QCOMPARE(r.value(QStringLiteral("back")).toArray(), before);
+
+		checkMirrored(before, r.value(QStringLiteral("v")).toArray(), true);
+		QVERIFY(r.value(QStringLiteral("vMirror")).toString()
+				!= r.value(QStringLiteral("hMirror")).toString());
+		QCOMPARE(r.value(QStringLiteral("undone")).toArray(), before);
+
+			//The save keeps the mirror, and only on that element
+		QVERIFY(r.value(QStringLiteral("saved")).toBool());
+		QFile file(saved);
+		QVERIFY(file.open(QIODevice::ReadOnly));
+		QDomDocument doc;
+		QVERIFY(bool(doc.setContent(&file)));
+		const QString element = r.value(QStringLiteral("element")).toString();
+		const QDomNodeList elements = doc.elementsByTagName(QStringLiteral("element"));
+		int mirrored_count = 0;
+		for (int i = 0; i < elements.size(); ++i) {
+			const QDomElement e = elements.at(i).toElement();
+			if (e.hasAttribute(QStringLiteral("mirror"))) {
+				++mirrored_count;
+				QCOMPARE(e.attribute(QStringLiteral("uuid")), element);
+				QCOMPARE(e.attribute(QStringLiteral("mirror")),
+						 r.value(QStringLiteral("vMirror")).toString());
+			}
+		}
+		QCOMPARE(mirrored_count, 1);
+
+		const QJsonObject reloaded = run(script(QStringLiteral(
+			"var f = %1, el = '%2';\n"
+			"qet.log('PROBE ' + JSON.stringify({t: terms(f, el), m: qet.elementMirror(f, el)}));\n")
+			.arg(r.value(QStringLiteral("folio")).toInt()).arg(element)), saved);
+		QCOMPARE(reloaded.value(QStringLiteral("m")).toString(),
+				 r.value(QStringLiteral("vMirror")).toString());
+		QCOMPARE(reloaded.value(QStringLiteral("t")).toArray(),
+				 r.value(QStringLiteral("v")).toArray());
+	}
+
+	/**
+		On a turned symbol a mirror of the folio is the other mirror of the
+		symbol itself, and its rotation does not change: a label kept
+		upright does not swing round.
+	*/
+	void turnedElement_data()
+	{
+		QTest::addColumn<bool>("vertical");
+		QTest::newRow("horizontal") << false;
+		QTest::newRow("vertical")   << true;
+	}
+
+	void turnedElement()
+	{
+		QFETCH(bool, vertical);
+		const QJsonObject r = run(script(QStringLiteral(
+			"var pick = null;\n"
+			"for (var f = 0; f < qet.folioCount() && !pick; f++) {\n"
+			"  var els = qet.elementUuids(f);\n"
+			"  for (var e = 0; e < els.length && !pick; e++) {\n"
+			"    var t = terms(f, els[e]);\n"
+			"    if (t.length >= 2 && t.some(function (p) { return p.x !== t[0].x; })\n"
+			"        && t.some(function (p) { return p.y !== t[0].y; })) pick = {f: f, e: els[e]};\n"
+			"  }\n"
+			"}\n"
+			"var f = pick.f, el = pick.e, out = {};\n"
+			"qet.rotateElement(f, el, 90);\n"
+			"out.before = terms(f, el);\n"
+			"qet.mirrorElement(f, el, %1);\n"
+			"out.after = terms(f, el); out.mirror = qet.elementMirror(f, el);\n"
+			"qet.log('PROBE ' + JSON.stringify(out));\n")
+			.arg(vertical ? QStringLiteral("true") : QStringLiteral("false"))),
+			QStringLiteral(QET_EXAMPLES_DIR "/perceuse.qet"));
+
+		QVERIFY2(!r.isEmpty(), "the script logged nothing");
+		checkMirrored(r.value(QStringLiteral("before")).toArray(),
+					  r.value(QStringLiteral("after")).toArray(), vertical);
+			//turned by 90 degrees, the symbol's own axes are the other way
+		QCOMPARE(r.value(QStringLiteral("mirror")).toString(),
+				 vertical ? QStringLiteral("horizontal") : QStringLiteral("vertical"));
+	}
+};
+
+QTEST_APPLESS_MAIN(tst_scriptmirror)
+
+#include "tst_scriptmirror.moc"