LibCore: Add CEventLoop and make LibGUI/GEventLoop inherit from it.

This is shaping up to be quite nice.

LibCore/CEventLoop.h

@@ -0,0 +1,76 @@
+#pragma once
+
+#include <AK/Badge.h>
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+#include <AK/Vector.h>
+#include <AK/WeakPtr.h>
+#include <sys/select.h>
+#include <time.h>
+
+class CEvent;
+class CObject;
+class GNotifier;
+
+class CEventLoop {
+public:
+    CEventLoop();
+    virtual ~CEventLoop();
+
+    int exec();
+
+    void post_event(CObject& receiver, OwnPtr<CEvent>&&);
+
+    static CEventLoop& main();
+    static CEventLoop& current();
+
+    bool running() const { return m_running; }
+
+    static int register_timer(CObject&, int milliseconds, bool should_reload);
+    static bool unregister_timer(int timer_id);
+
+    static void register_notifier(Badge<GNotifier>, GNotifier&);
+    static void unregister_notifier(Badge<GNotifier>, GNotifier&);
+
+    void quit(int);
+
+    virtual void take_pending_events_from(CEventLoop& other)
+    {
+        m_queued_events.append(move(other.m_queued_events));
+    }
+
+protected:
+    virtual void add_file_descriptors_for_select(fd_set&, int& max_fd) { UNUSED_PARAM(max_fd); }
+    virtual void process_file_descriptors_after_select(const fd_set&) { }
+    virtual void do_processing() { }
+
+private:
+    void wait_for_event();
+    void get_next_timer_expiration(timeval&);
+
+    struct QueuedEvent {
+        WeakPtr<CObject> receiver;
+        OwnPtr<CEvent> event;
+    };
+    Vector<QueuedEvent> m_queued_events;
+
+    bool m_running { false };
+    bool m_exit_requested { false };
+    int m_exit_code { 0 };
+
+    struct EventLoopTimer {
+        int timer_id { 0 };
+        int interval { 0 };
+        timeval fire_time;
+        bool should_reload { false };
+        WeakPtr<CObject> owner;
+
+        void reload();
+        bool has_expired() const;
+    };
+
+    static HashMap<int, OwnPtr<EventLoopTimer>>* s_timers;
+    static int s_next_timer_id;
+
+    static HashTable<GNotifier*>* s_notifiers;
+};