Add undo/redo support for folio add, delete, and reorder (#575)

Three new QUndoCommand subclasses (AddDiagramCommand, RemoveDiagramCommand,
MoveDiagramCommand) pushed onto the project's existing (already
project-scoped) undo stack, so folio structure edits are undoable
alongside every item-level edit already on that stack.

- QETProject::addDiagram()/detachDiagram() are the shared attach/detach
  primitives: they mutate the diagram list, connect/disconnect the two
  per-diagram signals set up at add time, and emit diagramAdded/
  diagramRemoved. AddDiagramCommand and RemoveDiagramCommand call these
  (via friend access) for both redo and undo, so a removed diagram is
  parked rather than destroyed -- it's only actually deleted if the
  command itself falls out of undo history while still detached.
- ProjectView reacts to diagramRemoved the same way it already reacted to
  diagramAdded (tearing down/rebuilding the tab), so both directions of
  both commands go through the same reactive path every other diagram
  listener (project database, cross-references, generic panel) already
  relies on.
- MoveDiagramCommand wraps a new ProjectView::setDiagramPosition(), which
  performs the tab move and the project's diagramOrderChanged() list
  reorder synchronously in one step, instead of relying on the queued
  tabMoved connection (needed for interactive drag-and-drop) to catch up
  later -- avoiding a second, redundant reorder from that queued call.
- Multi-folio delete and multi-folio move (QETDiagramEditor::removeDiagrams()
  and the moveDiagram*(QList<Diagram*>) batch slots) wrap their per-diagram
  loop in QUndoStack::beginMacro()/endMacro(), so a multi-select action is
  one undo step, matching current UX.
- Softened the delete confirmation's "this change is irreversible" wording
  now that it no longer is.

Verified headlessly (Xvfb + xdotool + scrot): add/undo/redo, delete/undo/
redo (single and multi-select, single undo step for the batch), and
move/undo/redo all behave correctly against a 7-folio project.

sources/undocommand/adddiagramcommand.cpp

@@ -0,0 +1,68 @@
+/*
+	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 "adddiagramcommand.h"
+
+#include "../qetproject.h"
+#include "../diagram.h"
+
+/**
+	@brief AddDiagramCommand::AddDiagramCommand
+	@param project : project the diagram is added to
+	@param diagram : the already constructed diagram to add (not yet part of any project's diagram list)
+	@param pos : position to insert the diagram at, -1 to append at the end
+	@param parent
+*/
+AddDiagramCommand::AddDiagramCommand(QETProject *project, Diagram *diagram, int pos, QUndoCommand *parent) :
+	QUndoCommand(parent),
+	m_project(project),
+	m_diagram(diagram),
+	m_position(pos)
+{
+	setText(QObject::tr("Ajouter un folio", "undo command text"));
+}
+
+/**
+	@brief AddDiagramCommand::~AddDiagramCommand
+	Destroy the diagram only if it is currently detached from the project
+	(i.e. this add was undone) -- otherwise the project owns it and will
+	destroy it itself.
+*/
+AddDiagramCommand::~AddDiagramCommand()
+{
+	if (m_owns_diagram && m_diagram) {
+		m_diagram->deleteLater();
+	}
+}
+
+void AddDiagramCommand::redo()
+{
+	if (!m_project || !m_diagram) {
+		return;
+	}
+	m_project->addDiagram(m_diagram, m_position);
+	m_owns_diagram = false;
+}
+
+void AddDiagramCommand::undo()
+{
+	if (!m_project || !m_diagram) {
+		return;
+	}
+	m_project->detachDiagram(m_diagram);
+	m_owns_diagram = true;
+}

sources/undocommand/adddiagramcommand.h

@@ -0,0 +1,52 @@
+/*
+	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 ADDDIAGRAMCOMMAND_H
+#define ADDDIAGRAMCOMMAND_H
+
+#include <QUndoCommand>
+#include <QPointer>
+
+class QETProject;
+class Diagram;
+
+/**
+	@brief The AddDiagramCommand class
+	Undo/redo support for adding a new folio (diagram) to a project.
+	Takes ownership of the (already constructed, not yet inserted) diagram:
+	redo() inserts it into the project, undo() detaches it again without
+	destroying it. The diagram is only actually destroyed when this command
+	itself is destroyed while the diagram is detached (i.e. while undone).
+*/
+class AddDiagramCommand : public QUndoCommand
+{
+	public:
+		AddDiagramCommand(QETProject *project, Diagram *diagram, int pos = -1, QUndoCommand *parent = nullptr);
+		~AddDiagramCommand() override;
+
+		void undo() override;
+		void redo() override;
+
+	private:
+		QPointer<QETProject> m_project;
+		Diagram *m_diagram;
+		int m_position;
+		/// true while the diagram is detached from the project (not currently in its diagram list)
+		bool m_owns_diagram = true;
+};
+
+#endif // ADDDIAGRAMCOMMAND_H

sources/undocommand/movediagramcommand.cpp

@@ -0,0 +1,56 @@
+/*
+	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 "movediagramcommand.h"
+
+#include "../projectview.h"
+#include "../qetproject.h"
+
+/**
+	@brief MoveDiagramCommand::MoveDiagramCommand
+	@param project_view : project view the diagram's tab belongs to
+	@param diagram : the diagram to move
+	@param new_position : target position (may be out of range, e.g. for a
+	x10/x100 move near either end -- ProjectView::setDiagramPosition() clamps
+	it the same way the underlying tab bar always has)
+	@param parent
+*/
+MoveDiagramCommand::MoveDiagramCommand(ProjectView *project_view, Diagram *diagram, int new_position, QUndoCommand *parent) :
+	QUndoCommand(parent),
+	m_project_view(project_view),
+	m_diagram(diagram),
+	m_old_position(project_view ? project_view->project()->folioIndex(diagram) : -1),
+	m_new_position(new_position)
+{
+	setText(QObject::tr("Déplacer un folio", "undo command text"));
+}
+
+void MoveDiagramCommand::redo()
+{
+	if (!m_project_view) {
+		return;
+	}
+	m_project_view->setDiagramPosition(m_diagram, m_new_position);
+}
+
+void MoveDiagramCommand::undo()
+{
+	if (!m_project_view) {
+		return;
+	}
+	m_project_view->setDiagramPosition(m_diagram, m_old_position);
+}

sources/undocommand/movediagramcommand.h

@@ -0,0 +1,49 @@
+/*
+	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 MOVEDIAGRAMCOMMAND_H
+#define MOVEDIAGRAMCOMMAND_H
+
+#include <QUndoCommand>
+#include <QPointer>
+
+class ProjectView;
+class Diagram;
+
+/**
+	@brief The MoveDiagramCommand class
+	Undo/redo support for reordering a folio (diagram) within a project's
+	tabs. Wraps ProjectView::setDiagramPosition(), which performs the tab
+	move and the matching (synchronous) project diagram-list reorder in one
+	step.
+*/
+class MoveDiagramCommand : public QUndoCommand
+{
+	public:
+		MoveDiagramCommand(ProjectView *project_view, Diagram *diagram, int new_position, QUndoCommand *parent = nullptr);
+
+		void undo() override;
+		void redo() override;
+
+	private:
+		QPointer<ProjectView> m_project_view;
+		Diagram *m_diagram;
+		int m_old_position;
+		int m_new_position;
+};
+
+#endif // MOVEDIAGRAMCOMMAND_H

sources/undocommand/removediagramcommand.cpp

@@ -0,0 +1,67 @@
+/*
+	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 "removediagramcommand.h"
+
+#include "../qetproject.h"
+#include "../diagram.h"
+
+/**
+	@brief RemoveDiagramCommand::RemoveDiagramCommand
+	@param project : project the diagram is removed from
+	@param diagram : the diagram to remove, currently part of \p project
+	@param parent
+*/
+RemoveDiagramCommand::RemoveDiagramCommand(QETProject *project, Diagram *diagram, QUndoCommand *parent) :
+	QUndoCommand(parent),
+	m_project(project),
+	m_diagram(diagram),
+	m_position(project ? project->folioIndex(diagram) : -1)
+{
+	setText(QObject::tr("Supprimer un folio", "undo command text"));
+}
+
+/**
+	@brief RemoveDiagramCommand::~RemoveDiagramCommand
+	Destroy the diagram only if it is currently detached from the project
+	(i.e. the removal is currently in effect) -- otherwise the project owns
+	it and will destroy it itself.
+*/
+RemoveDiagramCommand::~RemoveDiagramCommand()
+{
+	if (m_owns_diagram && m_diagram) {
+		m_diagram->deleteLater();
+	}
+}
+
+void RemoveDiagramCommand::redo()
+{
+	if (!m_project || !m_diagram) {
+		return;
+	}
+	m_project->detachDiagram(m_diagram);
+	m_owns_diagram = true;
+}
+
+void RemoveDiagramCommand::undo()
+{
+	if (!m_project || !m_diagram) {
+		return;
+	}
+	m_project->addDiagram(m_diagram, m_position);
+	m_owns_diagram = false;
+}

sources/undocommand/removediagramcommand.h

@@ -0,0 +1,53 @@
+/*
+	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 REMOVEDIAGRAMCOMMAND_H
+#define REMOVEDIAGRAMCOMMAND_H
+
+#include <QUndoCommand>
+#include <QPointer>
+
+class QETProject;
+class Diagram;
+
+/**
+	@brief The RemoveDiagramCommand class
+	Undo/redo support for removing a folio (diagram) from a project.
+	redo() detaches the diagram from the project (and, reactively, its
+	ProjectView tab) without destroying it; undo() reinserts it at its
+	original position. The diagram is only actually destroyed when this
+	command itself is destroyed while the diagram is detached (i.e. while
+	the removal is still in effect).
+*/
+class RemoveDiagramCommand : public QUndoCommand
+{
+	public:
+		RemoveDiagramCommand(QETProject *project, Diagram *diagram, QUndoCommand *parent = nullptr);
+		~RemoveDiagramCommand() override;
+
+		void undo() override;
+		void redo() override;
+
+	private:
+		QPointer<QETProject> m_project;
+		Diagram *m_diagram;
+		int m_position;
+		/// true while the diagram is detached from the project (i.e. the removal is in effect)
+		bool m_owns_diagram = false;
+};
+
+#endif // REMOVEDIAGRAMCOMMAND_H