Taskbar: More bringup work. We now see a basic window list.

Servers/WindowServer/WSAPITypes.h

@@ -91,6 +91,9 @@ struct WSAPI_ServerMessage {
         DidSetWallpaper,
         DidGetWallpaper,
         ScreenRectChanged,
+        WM_WindowAdded,
+        WM_WindowRemoved,
+        WM_WindowStateChanged,
     };
     Type type { Invalid };
     int window_id { -1 };
@@ -103,6 +106,11 @@ struct WSAPI_ServerMessage {
             int server_pid;
             WSAPI_Rect screen_rect;
         } greeting;
+        struct {
+            int client_id;
+            int window_id;
+            WSAPI_Rect rect;
+        } wm;
         struct {
             WSAPI_Rect rect;
         } screen;

Servers/WindowServer/WSMessage.h

@@ -26,6 +26,10 @@ public:
         WindowCloseRequest,
         WindowResized,
 
+        WM_WindowAdded,
+        WM_WindowRemoved,
+        WM_WindowStateChanged,
+
         __Begin_API_Client_Requests,
         APICreateMenubarRequest,
         APIDestroyMenubarRequest,
@@ -581,3 +585,62 @@ private:
     Rect m_old_rect;
     Rect m_rect;
 };
+
+class WSWMEvent : public WSMessage {
+public:
+    WSWMEvent(Type type, int client_id, int window_id)
+        : WSMessage(type)
+        , m_client_id(client_id)
+        , m_window_id(window_id)
+    {
+    }
+
+    int client_id() const { return m_client_id; }
+    int window_id() const { return m_window_id; }
+
+private:
+    int m_client_id;
+    int m_window_id;
+};
+
+class WSWMWindowAddedEvent : public WSWMEvent {
+public:
+    WSWMWindowAddedEvent(int client_id, int window_id, const String& title, const Rect& rect)
+        : WSWMEvent(WSMessage::WM_WindowAdded, client_id, window_id)
+        , m_title(title)
+        , m_rect(rect)
+    {
+    }
+
+    String title() const { return m_title; }
+    Rect rect() const { return m_rect; }
+
+private:
+    String m_title;
+    Rect m_rect;
+};
+
+class WSWMWindowRemovedEvent : public WSWMEvent {
+public:
+    WSWMWindowRemovedEvent(int client_id, int window_id)
+        : WSWMEvent(WSMessage::WM_WindowRemoved, client_id, window_id)
+    {
+    }
+};
+
+class WSWMWindowStateChangedEvent : public WSWMEvent {
+public:
+    WSWMWindowStateChangedEvent(int client_id, int window_id, const String& title, const Rect& rect)
+        : WSWMEvent(WSMessage::WM_WindowStateChanged, client_id, window_id)
+        , m_title(title)
+        , m_rect(rect)
+    {
+    }
+
+    String title() const { return m_title; }
+    Rect rect() const { return m_rect; }
+
+private:
+    String m_title;
+    Rect m_rect;
+};

Servers/WindowServer/WSWindow.cpp

@@ -28,6 +28,9 @@ WSWindow::WSWindow(WSClientConnection& client, WSWindowType window_type, int win
     , m_window_id(window_id)
     , m_icon(default_window_icon())
 {
+    // FIXME: This should not be hard-coded here.
+    if (m_type == WSWindowType::Taskbar)
+        m_listens_to_wm_events = true;
     WSWindowManager::the().add_window(*this);
 }
 
@@ -138,6 +141,36 @@ void WSWindow::on_message(const WSMessage& message)
         server_message.window.old_rect = static_cast<const WSResizeEvent&>(message).old_rect();
         server_message.window.rect = static_cast<const WSResizeEvent&>(message).rect();
         break;
+    case WSMessage::WM_WindowAdded: {
+        auto& added_event = static_cast<const WSWMWindowAddedEvent&>(message);
+        server_message.type = WSAPI_ServerMessage::Type::WM_WindowAdded;
+        server_message.wm.client_id = added_event.client_id();
+        server_message.wm.window_id = added_event.window_id();
+        ASSERT(added_event.title().length() < sizeof(server_message.text));
+        memcpy(server_message.text, added_event.title().characters(), added_event.title().length());
+        server_message.text_length = added_event.title().length();
+        server_message.wm.rect = added_event.rect();
+        break;
+    }
+    case WSMessage::WM_WindowRemoved: {
+        auto& removed_event = static_cast<const WSWMWindowRemovedEvent&>(message);
+        server_message.type = WSAPI_ServerMessage::Type::WM_WindowRemoved;
+        server_message.wm.client_id = removed_event.client_id();
+        server_message.wm.window_id = removed_event.window_id();
+        break;
+    }
+    case WSMessage::WM_WindowStateChanged: {
+        auto& changed_event = static_cast<const WSWMWindowStateChangedEvent&>(message);
+        server_message.type = WSAPI_ServerMessage::Type::WM_WindowStateChanged;
+        server_message.wm.client_id = changed_event.client_id();
+        server_message.wm.window_id = changed_event.window_id();
+        ASSERT(changed_event.title().length() < sizeof(server_message.text));
+        memcpy(server_message.text, changed_event.title().characters(), changed_event.title().length());
+        server_message.text_length = changed_event.title().length();
+        server_message.wm.rect = changed_event.rect();
+        break;
+    }
+
     default:
         break;
     }

Servers/WindowServer/WSWindow.h

@@ -20,6 +20,8 @@ public:
 
     bool is_blocked_by_modal_window() const;
 
+    bool listens_to_wm_events() const { return m_listens_to_wm_events; }
+
     WSClientConnection* client() { return m_client; }
     const WSClientConnection* client() const { return m_client; }
 
@@ -124,6 +126,7 @@ private:
     bool m_has_painted_since_last_resize { false };
     bool m_modal { false };
     bool m_resizable { false };
+    bool m_listens_to_wm_events { false };
     RetainPtr<GraphicsBitmap> m_backing_store;
     RetainPtr<GraphicsBitmap> m_last_backing_store;
     int m_window_id { -1 };

Servers/WindowServer/WSWindowManager.cpp

@@ -294,7 +294,7 @@ void get_cpu_usage(unsigned& busy, unsigned& idle)
     FILE* fp = fopen("/proc/all", "r");
     if (!fp) {
         perror("failed to open /proc/all");
-        exit(1);
+        ASSERT_NOT_REACHED();
     }
     for (;;) {
         char buf[BUFSIZ];
@@ -507,6 +507,12 @@ void WSWindowManager::add_window(WSWindow& window)
         set_active_window(&window);
     if (m_switcher.is_visible() && window.type() != WSWindowType::WindowSwitcher)
         m_switcher.refresh();
+
+    for_each_window_listening_to_wm_events([&window] (WSWindow& listener) {
+        if (window.client())
+            WSMessageLoop::the().post_message(listener, make<WSWMWindowAddedEvent>(window.client()->client_id(), window.window_id(), window.title(), window.rect()));
+        return IterationDecision::Continue;
+    });
 }
 
 void WSWindowManager::move_to_front_and_make_active(WSWindow& window)
@@ -534,6 +540,12 @@ void WSWindowManager::remove_window(WSWindow& window)
         set_active_window(*m_windows.begin());
     if (m_switcher.is_visible() && window.type() != WSWindowType::WindowSwitcher)
         m_switcher.refresh();
+
+    for_each_window_listening_to_wm_events([&window] (WSWindow& listener) {
+        if (window.client())
+            WSMessageLoop::the().post_message(listener, make<WSWMWindowRemovedEvent>(window.client()->client_id(), window.window_id()));
+        return IterationDecision::Continue;
+    });
 }
 
 void WSWindowManager::notify_title_changed(WSWindow& window)
@@ -542,6 +554,12 @@ void WSWindowManager::notify_title_changed(WSWindow& window)
     invalidate(outer_window_rect(window));
     if (m_switcher.is_visible())
         m_switcher.refresh();
+
+    for_each_window_listening_to_wm_events([&window] (WSWindow& listener) {
+        if (window.client())
+            WSMessageLoop::the().post_message(listener, make<WSWMWindowStateChangedEvent>(window.client()->client_id(), window.window_id(), window.title(), window.rect()));
+        return IterationDecision::Continue;
+    });
 }
 
 void WSWindowManager::notify_rect_changed(WSWindow& window, const Rect& old_rect, const Rect& new_rect)
@@ -553,6 +571,12 @@ void WSWindowManager::notify_rect_changed(WSWindow& window, const Rect& old_rect
     invalidate(outer_window_rect(new_rect));
     if (m_switcher.is_visible() && window.type() != WSWindowType::WindowSwitcher)
         m_switcher.refresh();
+
+    for_each_window_listening_to_wm_events([&window] (WSWindow& listener) {
+        if (window.client())
+            WSMessageLoop::the().post_message(listener, make<WSWMWindowStateChangedEvent>(window.client()->client_id(), window.window_id(), window.title(), window.rect()));
+        return IterationDecision::Continue;
+    });
 }
 
 void WSWindowManager::handle_menu_mouse_event(WSMenu& menu, const WSMouseEvent& event)

Servers/WindowServer/WSWindowManager.h

@@ -112,6 +112,7 @@ private:
     template<typename Callback> IterationDecision for_each_visible_window_of_type_from_front_to_back(WSWindowType, Callback);
     template<typename Callback> IterationDecision for_each_visible_window_from_front_to_back(Callback);
     template<typename Callback> IterationDecision for_each_visible_window_from_back_to_front(Callback);
+    template<typename Callback> void for_each_window_listening_to_wm_events(Callback);
     template<typename Callback> void for_each_active_menubar_menu(Callback);
     void close_current_menu();
     virtual void on_message(const WSMessage&) override;
@@ -265,3 +266,14 @@ IterationDecision WSWindowManager::for_each_visible_window_from_front_to_back(Ca
         return IterationDecision::Abort;
     return for_each_visible_window_of_type_from_front_to_back(WSWindowType::WindowSwitcher, callback);
 }
+
+template<typename Callback>
+void WSWindowManager::for_each_window_listening_to_wm_events(Callback callback)
+{
+    for (auto* window = m_windows_in_order.tail(); window; window = window->prev()) {
+        if (!window->listens_to_wm_events())
+            continue;
+        if (callback(*window) == IterationDecision::Abort)
+            return;
+    }
+}