Add saving and loading the configuration to a file (discussion #610)

Revives #640, closed only to clear a review backlog. Two entries in
the Configuration menu: "Enregistrer la configuration sous..." saves
the settings to a .conf file, "Charger une configuration..." replaces
them with one. The file is always ini format, so a profile made on one
platform loads on the others.

Changes from #640:
- Window sizes, positions and dock layouts (".../geometry",
  ".../state") and the recent-files lists stay out of a profile and
  are kept on load: they describe this computer, not a preference.
- A saved file carries a format marker; loading refuses files that
  QElectroTech did not save.
- Loading closes QElectroTech and asks the user to start it again,
  instead of starting a second copy: a second copy started while this
  one is still running hands its arguments over and exits (main.cpp).
- The colour dialog's custom colours are reloaded from the profile
  before quitting, since ~QETApp() saves them over the loaded ones.
- Both actions are registered with ShortcutManager, so they appear in
  command search and can be given a shortcut.
- The copy rules live in the header-only utils/configprofile.h and
  are unit tested (tst_configprofile).

Loading still replaces rather than merges: a setting the profile does
not have is removed, or switching profiles would keep settings from the
previous one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/qttest/CMakeLists.txt

@@ -111,6 +111,13 @@ add_test(NAME tst_alignment COMMAND tst_alignment)
 target_include_directories(tst_alignment PRIVATE ${QET_DIR}/sources)
 target_link_libraries(tst_alignment PRIVATE Qt::Test)
 
+# configprofile.h is header-only: which settings a saved configuration
+# profile carries, and how loading one replaces the live settings.
+add_executable(tst_configprofile tst_configprofile.cpp)
+add_test(NAME tst_configprofile COMMAND tst_configprofile)
+target_include_directories(tst_configprofile PRIVATE ${QET_DIR}/sources)
+target_link_libraries(tst_configprofile PRIVATE Qt::Test Qt::Gui)
+
 # itemgroups.cpp keeps group membership and the selection rule apart from
 # Diagram, so it is tested here on a plain scene of rectangles.
 add_executable(tst_itemgroups tst_itemgroups.cpp ${QET_DIR}/sources/itemgroups.cpp)

tests/qttest/tst_configprofile.cpp

@@ -0,0 +1,100 @@
+#include <QtTest>
+#include <QTemporaryDir>
+
+#include "utils/configprofile.h"
+
+class tst_configprofile : public QObject
+{
+	Q_OBJECT
+
+	QTemporaryDir m_dir;
+
+	QString path(const QString &name) const { return m_dir.filePath(name); }
+
+private slots:
+	void localKeys()
+	{
+		QVERIFY(ConfigProfile::isLocalKey("diagrameditor/geometry"));
+		QVERIFY(ConfigProfile::isLocalKey("elementeditor/state"));
+		QVERIFY(ConfigProfile::isLocalKey("projects-recentfiles/file1"));
+		QVERIFY(ConfigProfile::isLocalKey(ConfigProfile::marker_key));
+		QVERIFY(!ConfigProfile::isLocalKey("diagrameditor/Xgrid"));
+		QVERIFY(!ConfigProfile::isLocalKey("shortcuts/mainwindow.fullscreen"));
+		QVERIFY(!ConfigProfile::isLocalKey("masterpropertieswidget/plc-table-header-state"));
+	}
+
+	// Export leaves out window layout and recent files, and marks the file.
+	void exportLeavesOutLocalKeys()
+	{
+		QSettings live(path("live1.conf"), QSettings::IniFormat);
+		live.setValue("diagrameditor/Xgrid", 7);
+		live.setValue("lang", "de");
+		live.setValue("diagrameditor/geometry", QByteArray("xyz"));
+		live.setValue("projects-recentfiles/file1", "/home/a/b.qet");
+
+		QSettings file(path("profile1.conf"), QSettings::IniFormat);
+		QCOMPARE(ConfigProfile::exportTo(live, file), 2);
+		QVERIFY(ConfigProfile::isProfile(file));
+		QCOMPARE(file.value("diagrameditor/Xgrid").toInt(), 7);
+		QVERIFY(!file.contains("diagrameditor/geometry"));
+		QVERIFY(!file.contains("projects-recentfiles/file1"));
+	}
+
+	// Import replaces every setting, removes the ones the profile does not
+	// have, keeps window layout and recent files, and never copies the marker.
+	void importReplacesButKeepsLocal()
+	{
+		QSettings file(path("profile2.conf"), QSettings::IniFormat);
+		file.setValue("diagrameditor/Xgrid", 5);
+		file.setValue("diagrameditor/geometry", QByteArray("from-file"));
+		file.setValue(ConfigProfile::marker_key, 1);
+
+		QSettings live(path("live2.conf"), QSettings::IniFormat);
+		live.setValue("diagrameditor/Xgrid", 10);
+		live.setValue("lang", "fr");
+		live.setValue("diagrameditor/geometry", QByteArray("mine"));
+		live.setValue("projects-recentfiles/file1", "/home/a/b.qet");
+
+		ConfigProfile::importFrom(file, live);
+		QCOMPARE(live.value("diagrameditor/Xgrid").toInt(), 5);
+		QVERIFY(!live.contains("lang"));
+		QCOMPARE(live.value("diagrameditor/geometry").toByteArray(), QByteArray("mine"));
+		QCOMPARE(live.value("projects-recentfiles/file1").toString(), QString("/home/a/b.qet"));
+		QVERIFY(!live.contains(ConfigProfile::marker_key));
+	}
+
+	// Values survive the round trip with their types, including arrays.
+	void roundTrip()
+	{
+		QSettings a(path("a.conf"), QSettings::IniFormat);
+		a.setValue("print/default/fitinpage", true);
+		a.setValue("diagrameditor/sheet_background_color", QColor(12, 34, 56));
+		a.beginWriteArray("diagrameditor/defaultguides", 2);
+		a.setArrayIndex(0); a.setValue("pos", 100);
+		a.setArrayIndex(1); a.setValue("pos", 250);
+		a.endArray();
+
+		QSettings file(path("profile3.conf"), QSettings::IniFormat);
+		ConfigProfile::exportTo(a, file);
+		QSettings b(path("b.conf"), QSettings::IniFormat);
+		b.setValue("stray", 1);
+		ConfigProfile::importFrom(file, b);
+
+		QStringList ka = a.allKeys(), kb = b.allKeys();
+		ka.sort(); kb.sort();
+		QCOMPARE(kb, ka);
+		for (const QString &k : std::as_const(ka))
+			QCOMPARE(b.value(k), a.value(k));
+	}
+
+	void plainFileIsNotAProfile()
+	{
+		QSettings other(path("other.conf"), QSettings::IniFormat);
+		other.setValue("some/key", 1);
+		QVERIFY(!ConfigProfile::isProfile(other));
+	}
+};
+
+QTEST_GUILESS_MAIN(tst_configprofile)
+
+#include "tst_configprofile.moc"