Terminal+LibGUI: Make the terminal cursor blink.

Added a GTimer class to help with this. It's just a simple GObject subclass
that sets up an event loop timer and invokes a callback on timeout.

LibGUI/GTimer.cpp

@@ -0,0 +1,39 @@
+#include <LibGUI/GTimer.h>
+
+GTimer::GTimer(GObject* parent)
+    : GObject(parent)
+{
+}
+
+GTimer::~GTimer()
+{
+}
+
+void GTimer::start()
+{
+    start(m_interval);
+}
+
+void GTimer::start(int interval)
+{
+    if (m_active)
+        return;
+    start_timer(interval);
+    m_active = true;
+}
+
+void GTimer::stop()
+{
+    if (!m_active)
+        return;
+    stop_timer();
+    m_active = false;
+}
+
+void GTimer::timer_event(GTimerEvent&)
+{
+    if (m_single_shot)
+        stop();
+    if (on_timeout)
+        on_timeout();
+}

LibGUI/GTimer.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <LibGUI/GObject.h>
+#include <AK/Function.h>
+
+class GTimer final : public GObject {
+public:
+    explicit GTimer(GObject* parent = nullptr);
+    virtual ~GTimer() override;
+
+    void start();
+    void start(int interval);
+    void stop();
+
+    bool is_active() const { return m_active; }
+    int interval() const { return m_interval; }
+    void set_interval(int interval) { m_interval = interval; }
+
+    bool is_single_shot() const { return m_single_shot; }
+    void set_single_shot(bool single_shot) { m_single_shot = single_shot; }
+
+    Function<void()> on_timeout;
+
+    virtual const char* class_name() const override { return "GTimer"; }
+
+private:
+    virtual void timer_event(GTimerEvent&) override;
+
+    bool m_active { false };
+    bool m_single_shot { false };
+    int m_interval { 0 };
+};

LibGUI/Makefile

@@ -57,6 +57,7 @@ LIBGUI_OBJS = \
     GTreeView.o \
     GFileSystemModel.o \
     GSplitter.o \
+    GTimer.o \
     GWindow.o
 
 OBJS = $(SHAREDGRAPHICS_OBJS) $(LIBGUI_OBJS)