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.

Applications/Terminal/Terminal.cpp

@@ -21,6 +21,12 @@ Terminal::Terminal(int ptm_fd)
     : m_ptm_fd(ptm_fd)
     , m_notifier(ptm_fd, GNotifier::Read)
 {
+    m_cursor_blink_timer.set_interval(500);
+    m_cursor_blink_timer.on_timeout = [this] {
+        m_cursor_blink_state = !m_cursor_blink_state;
+        update_cursor();
+    };
+
     set_font(Font::default_fixed_width_font());
     m_notifier.on_ready_to_read = [this] (GNotifier& notifier) {
         byte buffer[BUFSIZ];
@@ -724,6 +730,12 @@ void Terminal::event(GEvent& event)
 {
     if (event.type() == GEvent::WindowBecameActive || event.type() == GEvent::WindowBecameInactive) {
         m_in_active_window = event.type() == GEvent::WindowBecameActive;
+        if (!m_in_active_window) {
+            m_cursor_blink_timer.stop();
+        } else {
+            m_cursor_blink_state = true;
+            m_cursor_blink_timer.start();
+        }
         invalidate_cursor();
         update();
     }
@@ -794,7 +806,7 @@ void Terminal::paint_event(GPaintEvent&)
             painter.fill_rect(row_rect(row), lookup_color(line.attributes[0].background_color).with_alpha(255 * m_opacity));
         }
         for (word column = 0; column < m_columns; ++column) {
-            bool should_reverse_fill_for_cursor = m_in_active_window && row == m_cursor_row && column == m_cursor_column;
+            bool should_reverse_fill_for_cursor = m_cursor_blink_state && m_in_active_window && row == m_cursor_row && column == m_cursor_column;
             auto& attribute = line.attributes[column];
             char ch = line.characters[column];
             auto character_rect = glyph_rect(row, column);
@@ -864,3 +876,9 @@ void Terminal::apply_size_increments_to_window(GWindow& window)
     window.set_size_increment({ font().glyph_width('x'), m_line_height });
     window.set_base_size({ m_inset * 2, m_inset * 2});
 }
+
+void Terminal::update_cursor()
+{
+    invalidate_cursor();
+    flush_dirty_lines();
+}

Applications/Terminal/Terminal.h

@@ -7,6 +7,7 @@
 #include <SharedGraphics/Rect.h>
 #include <LibGUI/GWidget.h>
 #include <LibGUI/GNotifier.h>
+#include <LibGUI/GTimer.h>
 
 class Font;
 
@@ -65,6 +66,7 @@ private:
     word rows() const { return m_rows; }
     Rect glyph_rect(word row, word column);
     Rect row_rect(word row);
+    void update_cursor();
 
     struct Attribute {
         Attribute() { reset(); }
@@ -154,6 +156,9 @@ private:
 
     float m_opacity { 1 };
     bool m_needs_background_fill { true };
+    bool m_cursor_blink_state { true };
 
     int m_glyph_width { 0 };
+
+    GTimer m_cursor_blink_timer;
 };

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)