LibGUI+WindowServer: Introduce new mouse tracking mechanism

Userland/Libraries/LibGUI/MouseTracker.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Badge.h>
+#include <AK/Function.h>
+#include <AK/IntrusiveList.h>
+#include <LibGUI/Forward.h>
+#include <LibGfx/Point.h>
+
+namespace GUI {
+
+class MouseTracker {
+public:
+    MouseTracker();
+    virtual ~MouseTracker();
+
+    static void track_mouse_move(Badge<WindowServerConnection>, Gfx::IntPoint const&);
+
+protected:
+    virtual void track_mouse_move(Gfx::IntPoint const&) = 0;
+
+private:
+    IntrusiveListNode<MouseTracker> m_list_node;
+    using List = IntrusiveList<MouseTracker, RawPtr<MouseTracker>, &MouseTracker::m_list_node>;
+    static List s_trackers;
+};
+
+}