Let menu change "Items to insert" also create new sections

When switching from LibreOffice splash to e.g. Writer, it creates an entirely new
section for us and then replaces the "root" menu with an alias to that new section.
Since we couldn't create new sections in this fashion we would get an alias to a
non-existing menu and break. This addresses this.

gmenu-dbusmenu-proxy/menu.cpp

@@ -391,29 +391,11 @@ void Menu::menuChanged(const GMenuChangeList &changes)
     DBusMenuItemList dirtyItems;
 
     for (const auto &change : changes) {
-        // shouldn't happen, it says only Start() subscribes to changes
-        if (!m_subscriptions.contains(change.subscription)) {
-            qCDebug(DBUSMENUPROXY) << "Got menu change for menu" << change.subscription << "that we are not subscribed to, subscribing now";
-            // LibreOffice doesn't give us a menu right away but takes a while and then signals us a change
-            start(change.subscription);
-            continue;
-        }
-
-        auto &menu = m_menus[change.subscription];
-
-        // TODO findSectionRef
-        for (GMenuItem &section : menu) {
-            if (section.section != change.menu) {
-                continue;
-            }
-
-            qDebug() << "change at" << change.changePosition << "remove" << change.itemsToRemoveCount << "INSERT" << change.itemsToInsert.count();
-
+        auto updateSection = [&](GMenuItem &section) {
             // Check if the amount of inserted items is identical to the items to be removed,
             // just update the existing items and signal a change for that.
             // LibreOffice tends to do that e.g. to update its Undo menu entry
             if (change.itemsToRemoveCount == change.itemsToInsert.count()) {
-                qDebug() << "is the same, let's just update";
                 for (int i = 0; i < change.itemsToInsert.count(); ++i) {
                     const auto &newItem = change.itemsToInsert.at(i);
 
@@ -437,13 +419,49 @@ void Menu::menuChanged(const GMenuChangeList &changes)
 
                 dirtyMenus.insert(treeStructureToInt(change.subscription, change.menu, 0));
             }
+        };
+
+        // shouldn't happen, it says only Start() subscribes to changes
+        if (!m_subscriptions.contains(change.subscription)) {
+            qCDebug(DBUSMENUPROXY) << "Got menu change for menu" << change.subscription << "that we are not subscribed to, subscribing now";
+            // LibreOffice doesn't give us a menu right away but takes a while and then signals us a change
+            start(change.subscription);
+            continue;
+        }
+
+        auto &menu = m_menus[change.subscription];
+
+        bool sectionFound = false;
+        // TODO findSectionRef
+        for (GMenuItem &section : menu) {
+            if (section.section != change.menu) {
+                continue;
+            }
+
+            qCInfo(DBUSMENUPROXY) << "Updating existing section" << change.menu << "in subscription" << change.subscription;
 
+            sectionFound = true;
+            updateSection(section);
             break;
         }
+
+        // Insert new section
+        if (!sectionFound) {
+            qCInfo(DBUSMENUPROXY) << "Creating new section" << change.menu << "in subscription" << change.subscription;
+
+            if (change.itemsToRemoveCount > 0) {
+                qCWarning(DBUSMENUPROXY) << "Menu change requested to remove items from a new (and as such empty) section";
+            }
+
+            GMenuItem newSection;
+            newSection.id = change.subscription;
+            newSection.section = change.menu;
+            updateSection(newSection);
+            menu.append(newSection);
+        }
     }
 
     if (!dirtyItems.isEmpty()) {
-        qDebug() << "Emit item properties changed for" << dirtyItems.count() << "after menu changed";
         emit ItemsPropertiesUpdated(dirtyItems, {});
     }