WindowServer: Add locking and fix coalesced invalidation race.

WSWindowManager::invalidate() had a bug where it would mark the entire screen
rect as dirty, but it wouldn't scheduled a deferred recompose.

This would cause any subsequent calls to invalidate(Rect) to be coalesced
with the pending compose, but the pending compose never happened.

Kernel/ProcessGUI.cpp

@@ -327,6 +327,5 @@ int Process::gui$menu_add_item(int menu_id, unsigned identifier, const char* tex
 
 int Process::gui$set_menubar(int menubar_id)
 {
-    kprintf("gui$set_menubar %d\n", menubar_id);
     return WSWindowManager::the().api$app_set_menubar(menubar_id);
 }

WindowServer/WSMenu.cpp

@@ -68,6 +68,7 @@ WSWindow& WSMenu::ensure_menu_window()
         }
 
         auto window = make<WSWindow>(*this);
+        WSWindowLocker locker(*window);
         window->set_rect(0, 0, width(), height());
         m_menu_window = move(window);
         draw();
@@ -78,6 +79,7 @@ WSWindow& WSMenu::ensure_menu_window()
 void WSMenu::draw()
 {
     ASSERT(menu_window());
+    WSWindowLocker locker(*menu_window());
     ASSERT(menu_window()->backing());
     Painter painter(*menu_window()->backing());
 
@@ -103,6 +105,7 @@ void WSMenu::draw()
 
 void WSMenu::on_window_message(WSMessage& message)
 {
+    WSWindowLocker locker(*menu_window());
     ASSERT(menu_window());
     if (message.type() == WSMessage::MouseMove) {
         auto* item = item_at(static_cast<WSMouseEvent&>(message).position());

WindowServer/WSMessageLoop.cpp

@@ -54,7 +54,7 @@ int WSMessageLoop::exec()
             auto* receiver = queued_message.receiver;
             auto& message = *queued_message.message;
 #ifdef WSEVENTLOOP_DEBUG
-            dbgprintf("WSMessageLoop: receiver{%p} message %u (%s)\n", receiver, (unsigned)event.type(), event.name());
+            dbgprintf("WSMessageLoop: receiver{%p} message %u\n", receiver, (unsigned)message.type());
 #endif
             if (!receiver) {
                 dbgprintf("WSMessage type %u with no receiver :(\n", message.type());
@@ -71,7 +71,7 @@ void WSMessageLoop::post_message(WSMessageReceiver* receiver, OwnPtr<WSMessage>&
 {
     LOCKER(m_lock);
 #ifdef WSEVENTLOOP_DEBUG
-    dbgprintf("WSMessageLoop::post_message: {%u} << receiver=%p, message=%p\n", m_queued_messages.size(), receiver, message.ptr());
+    dbgprintf("WSMessageLoop::post_message: {%u} << receiver=%p, message=%p (type=%u)\n", m_queued_messages.size(), receiver, message.ptr(), message->type());
 #endif
 
     if (message->type() == WSMessage::WM_ClientFinishedPaint) {
@@ -127,6 +127,7 @@ void WSMessageLoop::wait_for_message()
         params.timeout = nullptr;
     else
         params.timeout = &timeout;
+
     int rc = m_server_process->sys$select(&params);
     memory_barrier();
     if (rc < 0) {

WindowServer/WSWindowManager.cpp

@@ -197,6 +197,9 @@ WSWindowManager::WSWindowManager()
         };
     }
 
+    // NOTE: This ensures that the system menu has the correct dimensions.
+    set_current_menubar(nullptr);
+
     invalidate();
     compose();
 }
@@ -209,15 +212,15 @@ template<typename Callback>
 void WSWindowManager::for_each_active_menubar_menu(Callback callback)
 {
     callback(*m_system_menu);
-    m_current_menubar->for_each_menu(move(callback));
+    if (m_current_menubar)
+        m_current_menubar->for_each_menu(callback);
 }
 
 void WSWindowManager::set_current_menubar(WSMenuBar* menubar)
 {
     LOCKER(m_lock);
-    if (m_current_menubar == menubar)
-        return;
     m_current_menubar = menubar;
+    dbgprintf("[WM] Current menubar is now %p\n", menubar);
     int menu_margin = 16;
     Point next_menu_location { menu_margin / 2, 3 };
     for_each_active_menubar_menu([&] (WSMenu& menu) {
@@ -613,8 +616,6 @@ Rect WSWindowManager::menubar_rect() const
 
 void WSWindowManager::draw_menubar()
 {
-    if (!m_current_menubar)
-        return;
     m_back_painter->fill_rect(menubar_rect(), Color::LightGray);
     m_back_painter->draw_line({ 0, menubar_rect().bottom() }, { menubar_rect().right(), menubar_rect().bottom() }, Color::White);
     for_each_active_menubar_menu([&] (WSMenu& menu) {
@@ -685,7 +686,7 @@ void WSWindowManager::invalidate()
 {
     LOCKER(m_lock);
     m_dirty_rects.clear_with_capacity();
-    m_dirty_rects.append(m_screen_rect);
+    invalidate(m_screen_rect);
 }
 
 void WSWindowManager::invalidate(const Rect& a_rect)