WindowServer+LibGUI: Add support for nested menus

It's now possible to add a GMenu as a submenu of another GMenu.
Simply use the GMenu::add_submenu(NonnullOwnPtr<GMenu>) API :^)

The WindowServer now keeps track of a stack of open menus rather than
just one "current menu". This code needs a bit more work, but the basic
functionality is now here!

Libraries/LibGUI/GMenu.cpp

@@ -39,15 +39,25 @@ void GMenu::add_action(NonnullRefPtr<GAction> action)
 #endif
 }
 
+void GMenu::add_submenu(NonnullOwnPtr<GMenu> submenu)
+{
+    m_items.append(make<GMenuItem>(m_menu_id, move(submenu)));
+}
+
 void GMenu::add_separator()
 {
     m_items.append(make<GMenuItem>(m_menu_id, GMenuItem::Separator));
 }
 
-void GMenu::popup(const Point& screen_position)
+void GMenu::realize_if_needed()
 {
     if (m_menu_id == -1)
         realize_menu();
+}
+
+void GMenu::popup(const Point& screen_position)
+{
+    realize_if_needed();
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::PopupMenu;
     request.menu.menu_id = m_menu_id;
@@ -87,14 +97,34 @@ int GMenu::realize_menu()
             WSAPI_ClientMessage request;
             request.type = WSAPI_ClientMessage::Type::AddMenuSeparator;
             request.menu.menu_id = m_menu_id;
+            request.menu.submenu_id = -1;
             GWindowServerConnection::the().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuSeparator);
             continue;
         }
+        if (item.type() == GMenuItem::Submenu) {
+            auto& submenu = *item.submenu();
+            submenu.realize_if_needed();
+            WSAPI_ClientMessage request;
+            request.type = WSAPI_ClientMessage::Type::AddMenuItem;
+            request.menu.menu_id = m_menu_id;
+            request.menu.submenu_id = submenu.menu_id();
+            request.menu.identifier = i;
+            // FIXME: It should be possible to disable a submenu.
+            request.menu.enabled = true;
+            request.menu.checkable = false;
+            request.menu.checked = false;
+            ASSERT(submenu.name().length() < (ssize_t)sizeof(request.text));
+            strcpy(request.text, submenu.name().characters());
+            request.text_length = submenu.name().length();
+            GWindowServerConnection::the().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuItem);
+            continue;
+        }
         if (item.type() == GMenuItem::Action) {
             auto& action = *item.action();
             WSAPI_ClientMessage request;
             request.type = WSAPI_ClientMessage::Type::AddMenuItem;
             request.menu.menu_id = m_menu_id;
+            request.menu.submenu_id = -1;
             request.menu.identifier = i;
             request.menu.enabled = action.is_enabled();
             request.menu.checkable = action.is_checkable();

Libraries/LibGUI/GMenu.h

@@ -15,10 +15,13 @@ public:
 
     static GMenu* from_menu_id(int);
 
+    const String& name() const { return m_name; }
+
     GAction* action_at(int);
 
     void add_action(NonnullRefPtr<GAction>);
     void add_separator();
+    void add_submenu(NonnullOwnPtr<GMenu>);
 
     void popup(const Point& screen_position);
     void dismiss();
@@ -31,6 +34,7 @@ private:
     int menu_id() const { return m_menu_id; }
     int realize_menu();
     void unrealize_menu();
+    void realize_if_needed();
 
     int m_menu_id { -1 };
     String m_name;

Libraries/LibGUI/GMenuItem.cpp

@@ -1,5 +1,6 @@
 #include <LibGUI/GAction.h>
 #include <LibGUI/GEventLoop.h>
+#include <LibGUI/GMenu.h>
 #include <LibGUI/GMenuItem.h>
 #include <WindowServer/WSAPITypes.h>
 
@@ -21,6 +22,13 @@ GMenuItem::GMenuItem(unsigned menu_id, NonnullRefPtr<GAction>&& action)
         m_checked = m_action->is_checked();
 }
 
+GMenuItem::GMenuItem(unsigned menu_id, NonnullOwnPtr<GMenu>&& submenu)
+    : m_type(Submenu)
+    , m_menu_id(menu_id)
+    , m_submenu(move(submenu))
+{
+}
+
 GMenuItem::~GMenuItem()
 {
     if (m_action)

Libraries/LibGUI/GMenuItem.h

@@ -2,6 +2,8 @@
 
 #include <AK/AKString.h>
 #include <AK/Badge.h>
+#include <AK/NonnullOwnPtr.h>
+#include <AK/OwnPtr.h>
 
 class GAction;
 class GMenu;
@@ -11,11 +13,13 @@ public:
     enum Type {
         Invalid,
         Action,
-        Separator
+        Separator,
+        Submenu,
     };
 
     GMenuItem(unsigned menu_id, Type);
     GMenuItem(unsigned menu_id, NonnullRefPtr<GAction>&&);
+    GMenuItem(unsigned menu_id, NonnullOwnPtr<GMenu>&&);
     ~GMenuItem();
 
     Type type() const { return m_type; }
@@ -24,6 +28,9 @@ public:
     GAction* action() { return m_action.ptr(); }
     unsigned identifier() const { return m_identifier; }
 
+    GMenu* submenu() { return m_submenu.ptr(); }
+    const GMenu* submenu() const { return m_submenu.ptr(); }
+
     bool is_checkable() const { return m_checkable; }
     void set_checkable(bool checkable) { m_checkable = checkable; }
 
@@ -46,4 +53,5 @@ private:
     bool m_checkable { false };
     bool m_checked { false };
     RefPtr<GAction> m_action;
+    OwnPtr<GMenu> m_submenu;
 };