From 059d179d9b3021aabfe12890c4a10abb08e92960 Mon Sep 17 00:00:00 2001
From: Andre Rummler <andre.rummler@cern.ch>
Date: Fri, 18 Sep 2026 18:28:48 +0200
Subject: [PATCH] Fix: a) Project stayed in modified state even after undoing
 all changes. b) Saving the project deleted the undo stack.

---
 sources/projectview.cpp      |  5 ++++-
 sources/qetdiagrameditor.cpp |  2 +-
 sources/qetproject.cpp       |  4 +++-
 sources/qetproject.h         | 21 ++++++++++++++++++++-
 4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/sources/projectview.cpp b/sources/projectview.cpp
index 768fb816b..7f44b6913 100644
--- a/sources/projectview.cpp
+++ b/sources/projectview.cpp
@@ -726,7 +726,10 @@ QETResult ProjectView::doSave()
 	// write to file
 	QETResult result = m_project -> write();
 	updateWindowTitle();
-	project()->undoStack()->clear();
+	// This marks the stack's current index as the new "saved" point (so isClean()/cleanChanged() correctly
+	// resume tracking unsaved changes from here) without discarding the undo history. Edits made before this save 
+	// stay undoable for the rest of the session.
+	project()->undoStack()->setClean();
 	return(result);
 }
 
diff --git a/sources/qetdiagrameditor.cpp b/sources/qetdiagrameditor.cpp
index d1a4be91b..596663a3a 100644
--- a/sources/qetdiagrameditor.cpp
+++ b/sources/qetdiagrameditor.cpp
@@ -2840,7 +2840,7 @@ void QETDiagramEditor::updateWindowModifiedState()
 		setWindowTitle(QString("%1[*] - %2").arg(
 			project->pathNameTitle(),
 			tr("QElectroTech", "window title")));
-		setWindowModified(project->projectOptionsWereModified());
+		setWindowModified(project->projectWasModified());
 	} else {
 		setWindowTitle(tr("QElectroTech", "window title"));
 		setWindowModified(false);
diff --git a/sources/qetproject.cpp b/sources/qetproject.cpp
index 18afbdde6..6d0601b94 100644
--- a/sources/qetproject.cpp
+++ b/sources/qetproject.cpp
@@ -534,7 +534,9 @@ QString QETProject::pathNameTitle() const
 			)
 		).arg(final_title);
 	}
-	if (m_modified) {
+	// Same condition as projectWasModified(): project-options changeg (m_modified) OR the undo stack sitting away from
+	// its clean index. 
+	if (m_modified || !m_undo_stack->isClean()) {
 		final_title = QString(
 			tr(
 				"%1 [modifié]",
diff --git a/sources/qetproject.h b/sources/qetproject.h
index 91339c8ee..e898a65e6 100644
--- a/sources/qetproject.h
+++ b/sources/qetproject.h
@@ -252,7 +252,26 @@ class QETProject : public QObject
 		void updateDiagramsTitleBlockTemplate(TitleBlockTemplatesCollection *, const QString &);
 		void removeDiagramsTitleBlockTemplate(TitleBlockTemplatesCollection *, const QString &);
 		void usedTitleBlockTemplateChanged(const QString &);
-		void undoStackChanged (bool a) {if (!a) setModified(true);}
+		/* Deliberately does NOT touch m_modified: m_modified /
+		 * setModified() track project-OPTIONS changes only (see
+		 * projectOptionsWereModified()), which have no undo
+		 * entry and so must stay set until an explicit write().
+		 * Diagram-content changes are tracked by the undo
+		 * stack's own clean index instead, and projectWasModified()
+		 * already ORs the two together -- that combined value is
+		 * what actually answers "does this project have unsaved
+		 * changes", so re-derive and broadcast it here on every
+		 * clean/dirty transition (covering, in particular, an
+		 * Undo that walks the stack back to its clean index).
+		 * Latching m_modified itself to the undo stack's dirty
+		 * state, the way this slot did before, is a one-way trap:
+		 * cleanChanged(true) would never come back through here
+		 * to un-set it, so a plain content edit stayed marked as
+		 * unsaved even after being fully undone. */
+		void undoStackChanged (bool /*a*/) {
+			emit projectModified(this, projectWasModified());
+			emit projectInformationsChanged(this);
+		}
 
 	private:
 		void readProjectXml(QDomDocument &xml_project);