Plumb menu item activation events from WindowServer to clients.

GMenu now has an "on_item_activation" callback that fires whenever one
of its items are activated. The menu item identifier is used to distinguish
between items.

Use this to implement font switching in Terminal. :^)

LibGUI/GEventLoop.cpp

@@ -3,6 +3,7 @@
 #include "GObject.h"
 #include "GWindow.h"
 #include <LibGUI/GNotifier.h>
+#include <LibGUI/GMenu.h>
 #include <LibC/unistd.h>
 #include <LibC/stdio.h>
 #include <LibC/fcntl.h>
@@ -147,6 +148,21 @@ void GEventLoop::handle_mouse_event(const GUI_Event& event, GWindow& window)
     post_event(&window, make<GMouseEvent>(type, event.mouse.position, event.mouse.buttons, button));
 }
 
+void GEventLoop::handle_menu_event(const GUI_Event& event)
+{
+    if (event.type == GUI_Event::Type::MenuItemActivated) {
+        auto* menu = GMenu::from_menu_id(event.menu.menu_id);
+        if (!menu) {
+            dbgprintf("GEventLoop received event for invalid window ID %d\n", event.window_id);
+            return;
+        }
+        if (menu->on_item_activation)
+            menu->on_item_activation(event.menu.identifier);
+        return;
+    }
+    ASSERT_NOT_REACHED();
+}
+
 void GEventLoop::wait_for_event()
 {
     fd_set rfds;
@@ -219,6 +235,13 @@ void GEventLoop::wait_for_event()
         if (nread == 0)
             break;
         assert(nread == sizeof(event));
+
+        switch (event.type) {
+        case GUI_Event::MenuItemActivated:
+            handle_menu_event(event);
+            continue;
+        }
+
         auto* window = GWindow::from_window_id(event.window_id);
         if (!window) {
             dbgprintf("GEventLoop received event for invalid window ID %d\n", event.window_id);
@@ -244,6 +267,8 @@ void GEventLoop::wait_for_event()
         case GUI_Event::Type::KeyUp:
             handle_key_event(event, *window);
             break;
+        default:
+            break;
         }
     }
 }

LibGUI/GEventLoop.h

@@ -41,6 +41,7 @@ private:
     void handle_key_event(const GUI_Event&, GWindow&);
     void handle_window_activation_event(const GUI_Event&, GWindow&);
     void handle_window_close_request_event(const GUI_Event&, GWindow&);
+    void handle_menu_event(const GUI_Event&);
 
     void get_next_timer_expiration(timeval&);
 

LibGUI/GMenu.cpp

@@ -1,5 +1,22 @@
 #include <LibGUI/GMenu.h>
 #include <LibC/gui.h>
+#include <AK/HashMap.h>
+
+static HashMap<int, GMenu*>& all_menus()
+{
+    static HashMap<int, GMenu*>* map;
+    if (!map)
+        map = new HashMap<int, GMenu*>();
+    return *map;
+}
+
+GMenu* GMenu::from_menu_id(int menu_id)
+{
+    auto it = all_menus().find(menu_id);
+    if (it == all_menus().end())
+        return nullptr;
+    return (*it).value;
+}
 
 GMenu::GMenu(const String& name)
     : m_name(name)
@@ -9,6 +26,7 @@ GMenu::GMenu(const String& name)
 GMenu::~GMenu()
 {
     if (m_menu_id) {
+        all_menus().remove(m_menu_id);
         gui_menu_destroy(m_menu_id);
         m_menu_id = 0;
     }
@@ -34,5 +52,6 @@ int GMenu::realize_menu()
         else if (item.type() == GMenuItem::Text)
             gui_menu_add_item(m_menu_id, item.identifier(), item.text().characters());
     }
+    all_menus().set(m_menu_id, this);
     return m_menu_id;
 }

LibGUI/GMenu.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <LibGUI/GMenuItem.h>
+#include <AK/Function.h>
 #include <AK/Vector.h>
 
 class GMenu {
@@ -8,9 +9,13 @@ public:
     explicit GMenu(const String& name);
     ~GMenu();
 
+    static GMenu* from_menu_id(int);
+
     void add_item(unsigned identifier, const String& text);
     void add_separator();
 
+    Function<void(unsigned)> on_item_activation;
+
 private:
     friend class GMenuBar;
     int menu_id() const { return m_menu_id; }

LibGUI/GWidget.cpp

@@ -234,6 +234,7 @@ void GWidget::set_font(RetainPtr<Font>&& font)
         m_font = Font::default_font();
     else
         m_font = move(font);
+    update();
 }
 
 void GWidget::set_global_cursor_tracking(bool enabled)