Add a Toolbars settings page: icon size, text with icons, lock

A new page in Configurer QElectroTech, "Barres d'outils", sets for
every window (folio editor, element editor, title block editor):
- the icon size: default, 16, 24, 32 or 48 px
- the buttons: icon only, text beside the icon, or text under it
- locking the toolbars so they can't be dragged out of place

OK applies it to the open windows at once. The defaults are Qt's
own, and a default value removes its key, so nothing changes for
anyone who never opens the page. A toolbar inside a panel is left
alone; only the window's own toolbars are locked.

New test tst_toolbarsettings: defaults change nothing, saved values
reach every toolbar of an open window, back to defaults removes the
keys.

Third stage of discussion #1319.

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

sources/toolbarsettings.cpp

@@ -0,0 +1,102 @@
+/*
+	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 "toolbarsettings.h"
+
+#include <QApplication>
+#include <QMainWindow>
+#include <QSettings>
+#include <QToolBar>
+
+namespace {
+	const QString ICON_SIZE    = QStringLiteral("toolbars/icon_size");
+	const QString BUTTON_STYLE = QStringLiteral("toolbars/button_style");
+	const QString LOCKED       = QStringLiteral("toolbars/locked");
+}
+
+int ToolbarSettings::iconSize()
+{
+	return QSettings().value(ICON_SIZE, 0).toInt();
+}
+
+Qt::ToolButtonStyle ToolbarSettings::buttonStyle()
+{
+	const int style = QSettings().value(BUTTON_STYLE, int(Qt::ToolButtonIconOnly)).toInt();
+	switch (style) {
+		case Qt::ToolButtonTextBesideIcon:
+		case Qt::ToolButtonTextUnderIcon:
+			return Qt::ToolButtonStyle(style);
+		default:
+			return Qt::ToolButtonIconOnly;
+	}
+}
+
+bool ToolbarSettings::locked()
+{
+	return QSettings().value(LOCKED, false).toBool();
+}
+
+/**
+	@brief ToolbarSettings::save
+	Store the three values; a default value removes its key.
+*/
+void ToolbarSettings::save(int icon_size, Qt::ToolButtonStyle style, bool locked)
+{
+	QSettings settings;
+	if (icon_size > 0) settings.setValue(ICON_SIZE, icon_size);
+	else settings.remove(ICON_SIZE);
+	if (style != Qt::ToolButtonIconOnly) settings.setValue(BUTTON_STYLE, int(style));
+	else settings.remove(BUTTON_STYLE);
+	if (locked) settings.setValue(LOCKED, true);
+	else settings.remove(LOCKED);
+}
+
+/**
+	@brief ToolbarSettings::applyTo
+	Apply the settings to \a window and its toolbars. The window passes
+	its icon size and button style on to every toolbar that has none of
+	its own; an invalid size gives the style's default back.
+*/
+void ToolbarSettings::applyTo(QMainWindow *window)
+{
+	if (!window) {
+		return;
+	}
+	const int size = iconSize();
+	window->setIconSize(size > 0 ? QSize(size, size) : QSize());
+	window->setToolButtonStyle(buttonStyle());
+	const bool movable = !locked();
+	for (QToolBar *toolbar : window->findChildren<QToolBar *>()) {
+			//Not a toolbar inside a panel: only the window's own
+		if (window->toolBarArea(toolbar) != Qt::NoToolBarArea) {
+			toolbar->setMovable(movable);
+		}
+	}
+}
+
+/**
+	@brief ToolbarSettings::applyToAll
+	Apply the settings to every open window, after they change.
+*/
+void ToolbarSettings::applyToAll()
+{
+	for (QWidget *widget : QApplication::topLevelWidgets()) {
+		if (auto *window = qobject_cast<QMainWindow *>(widget)) {
+			applyTo(window);
+		}
+	}
+}