Fix restoreState() for QETElementEditor and QETTitleBlockTemplateEditor on Qt6

Apply the same split readSettings()/readSettingsState() pattern from
QETDiagramEditor to the other two main windows:
- QETElementEditor: split in constructor, call readSettingsState() after show()
- QETTitleBlockTemplateEditor: split readSettings(), callers call
  readSettingsState() after show() (newTemplate + 2x openTitleBlockTemplate)
- Remove destructive settings.remove() guards that would delete saved
  state on every Qt6 launch when restoreState() fails before show()

Co-authored-by: ispyisail

sources/editor/ui/qetelementeditor.cpp

@@ -77,8 +77,9 @@ QETElementEditor::QETElementEditor(QWidget *parent) :
 	//ui->m_display_menu->insertMenu(ui->m_zoom_in_action, menu);
 
 	setWindowState(Qt::WindowMaximized);
-	readSettings();
+	readSettings();  // restoreGeometry before show()
 	show();
+	readSettingsState();  // restoreState() must be called after show() in Qt6
 }
 
 /**
@@ -950,20 +951,28 @@ void QETElementEditor::readSettings()
 		restoreGeometry(geometry.toByteArray());
 	}
 
+	auto data = m_elmt_scene->elementData();
+	data.m_drawing_information = settings.value("elementeditor/default-informations", "").toString();
+	m_elmt_scene->setElementData(data);
+}
+
+/**
+ * @brief QETElementEditor::readSettingsState
+ * Restore the window state (docks, toolbars).
+ * Must be called AFTER show() in Qt6 for restoreState() to work correctly.
+ */
+void QETElementEditor::readSettingsState()
+{
+	QSettings settings;
+
 	QVariant state = settings.value("elementeditor/state");
 	if (state.isValid()) {
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
-		if (!restoreState(state.toByteArray())) {
-			settings.remove("elementeditor/state");
-		}
+		restoreState(state.toByteArray());
 #else
 		restoreState(state.toByteArray());
 #endif
 	}
-
-	auto data = m_elmt_scene->elementData();
-	data.m_drawing_information = settings.value("elementeditor/default-informations", "").toString();
-	m_elmt_scene->setElementData(data);
 }
 
 /**

sources/editor/ui/qetelementeditor.h

@@ -116,6 +116,7 @@ class QETElementEditor : public QMainWindow
 	private:
 		bool canClose();
 		void readSettings();
+		void readSettingsState();
 		void writeSettings() const;
 		void setupActions();
 		void updateAction();

sources/qetapp.cpp

@@ -1975,6 +1975,7 @@ void QETApp::openTitleBlockTemplate(const TitleBlockTemplateLocation &location,
 	qet_template_editor -> setOpenForDuplication(duplicate);
 	qet_template_editor -> edit(location);
 	qet_template_editor -> show();
+	qet_template_editor -> readSettingsState();  // must run after show() in Qt6
 }
 
 /**
@@ -1986,6 +1987,7 @@ void QETApp::openTitleBlockTemplate(const QString &filepath) {
 	QETTitleBlockTemplateEditor *qet_template_editor = new QETTitleBlockTemplateEditor();
 	qet_template_editor -> edit(filepath);
 	qet_template_editor -> show();
+	qet_template_editor -> readSettingsState();  // must run after show() in Qt6
 }
 
 /**

sources/titleblock/qettemplateeditor.cpp

@@ -358,6 +358,7 @@ void QETTitleBlockTemplateEditor::newTemplate()
 	QETTitleBlockTemplateEditor *qet_template_editor = new QETTitleBlockTemplateEditor();
 	qet_template_editor -> edit(TitleBlockTemplateLocation());
 	qet_template_editor -> show();
+	qet_template_editor -> readSettingsState();  // must run after show() in Qt6
 }
 
 /**
@@ -645,14 +646,23 @@ void QETTitleBlockTemplateEditor::readSettings()
 	// window size and position
 	QVariant geometry = settings.value("titleblocktemplateeditor/geometry");
 	if (geometry.isValid()) restoreGeometry(geometry.toByteArray());
+}
+
+/**
+	@brief QETTitleBlockTemplateEditor::readSettingsState
+	Restore the window state (docks, toolbars).
+	Must be called AFTER show() in Qt6 for restoreState() to work correctly
+	-- callers are responsible for calling this after show(), since this
+	window isn't shown by its own constructor.
+*/
+void QETTitleBlockTemplateEditor::readSettingsState()
+{
+	QSettings settings;
 
-	// window state (toolbars, docks...)
 	QVariant state = settings.value("titleblocktemplateeditor/state");
 	if (state.isValid()) {
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
-		if (!restoreState(state.toByteArray())) {
-			settings.remove("titleblocktemplateeditor/state");
-		}
+		restoreState(state.toByteArray());
 #else
 		restoreState(state.toByteArray());
 #endif

sources/titleblock/qettemplateeditor.h

@@ -108,6 +108,7 @@ class QETTitleBlockTemplateEditor : public QETMainWindow {
 
 	public slots:
 	void readSettings();
+	void readSettingsState();
 	void writeSettings();
 	void selectedCellsChanged(const QList<TitleBlockCell *>&);
 	void duplicateCurrentLocation();