Port Terminal to LibGUI.

To facilitate listening for action on arbitrary file descriptors,
I've added a GNotifier class. It's quite simple but very useful:

GNotifier notifier(fd, GNotifier::Read);
notifier.on_ready_to_read = [this] (GNotifier& fd) {
    // read from fd or whatever else you like :^)
};

The callback will get invoked by GEventLoop when select() says we
have something to read on the fd.

LibGUI/GEventLoop.cpp

@@ -2,6 +2,7 @@
 #include "GEvent.h"
 #include "GObject.h"
 #include "GWindow.h"
+#include <LibGUI/GNotifier.h>
 #include <LibC/unistd.h>
 #include <LibC/stdio.h>
 #include <LibC/fcntl.h>
@@ -60,7 +61,7 @@ int GEventLoop::exec()
             auto* receiver = queued_event.receiver;
             auto& event = *queued_event.event;
 #ifdef GEVENTLOOP_DEBUG
-            dbgprintf("GEventLoop: GObject{%p} event %u (%s)\n", receiver, (unsigned)event.type(), event.name());
+            dbgprintf("GEventLoop: %s{%p} event %u\n", receiver->class_name(), receiver, (unsigned)event.type());
 #endif
             if (!receiver) {
                 switch (event.type()) {
@@ -149,12 +150,31 @@ void GEventLoop::handle_mouse_event(const GUI_Event& event, GWindow& window)
 void GEventLoop::wait_for_event()
 {
     fd_set rfds;
+    fd_set wfds;
     FD_ZERO(&rfds);
-    FD_SET(m_event_fd, &rfds);
+    FD_ZERO(&wfds);
+
+    int max_fd = 0;
+    auto add_fd_to_set = [&max_fd] (int fd, fd_set& set){
+        FD_SET(fd, &set);
+        if (fd > max_fd)
+            max_fd = fd;
+    };
+
+    add_fd_to_set(m_event_fd, rfds);
+    for (auto& notifier : m_notifiers) {
+        if (notifier->event_mask() & GNotifier::Read)
+            add_fd_to_set(notifier->fd(), rfds);
+        if (notifier->event_mask() & GNotifier::Write)
+            add_fd_to_set(notifier->fd(), wfds);
+        if (notifier->event_mask() & GNotifier::Exceptional)
+            ASSERT_NOT_REACHED();
+    }
+
     struct timeval timeout = { 0, 0 };
     if (!m_timers.is_empty())
         get_next_timer_expiration(timeout);
-    int rc = select(m_event_fd + 1, &rfds, nullptr, nullptr, (m_queued_events.is_empty() && m_timers.is_empty()) ? nullptr : &timeout);
+    int rc = select(m_event_fd + 1, &rfds, &wfds, nullptr, (m_queued_events.is_empty() && m_timers.is_empty()) ? nullptr : &timeout);
     if (rc < 0) {
         ASSERT_NOT_REACHED();
     }
@@ -175,6 +195,17 @@ void GEventLoop::wait_for_event()
         }
     }
 
+    for (auto& notifier : m_notifiers) {
+        if (FD_ISSET(notifier->fd(), &rfds)) {
+            if (notifier->on_ready_to_read)
+                notifier->on_ready_to_read(*notifier);
+        }
+        if (FD_ISSET(notifier->fd(), &wfds)) {
+            if (notifier->on_ready_to_write)
+                notifier->on_ready_to_write(*notifier);
+        }
+    }
+
     if (!FD_ISSET(m_event_fd, &rfds))
         return;
 
@@ -266,3 +297,13 @@ bool GEventLoop::unregister_timer(int timer_id)
     m_timers.remove(it);
     return true;
 }
+
+void GEventLoop::register_notifier(Badge<GNotifier>, GNotifier& notifier)
+{
+    m_notifiers.set(&notifier);
+}
+
+void GEventLoop::unregister_notifier(Badge<GNotifier>, GNotifier& notifier)
+{
+    m_notifiers.remove(&notifier);
+}

LibGUI/GEventLoop.h

@@ -1,11 +1,13 @@
 #pragma once
 
 #include "GEvent.h"
+#include <AK/Badge.h>
 #include <AK/HashMap.h>
 #include <AK/OwnPtr.h>
 #include <AK/Vector.h>
 
 class GObject;
+class GNotifier;
 class GWindow;
 struct GUI_Event;
 
@@ -27,6 +29,9 @@ public:
     int register_timer(GObject&, int milliseconds, bool should_reload);
     bool unregister_timer(int timer_id);
 
+    void register_notifier(Badge<GNotifier>, GNotifier&);
+    void unregister_notifier(Badge<GNotifier>, GNotifier&);
+
     void exit(int);
 
 private:
@@ -64,4 +69,5 @@ private:
     };
 
     HashMap<int, OwnPtr<EventLoopTimer>> m_timers;
+    HashTable<GNotifier*> m_notifiers;
 };

LibGUI/GNotifier.cpp

@@ -0,0 +1,15 @@
+#include <LibGUI/GNotifier.h>
+#include <LibGUI/GEventLoop.h>
+
+GNotifier::GNotifier(int fd, unsigned event_mask)
+    : m_fd(fd)
+    , m_event_mask(event_mask)
+{
+    GEventLoop::main().register_notifier(Badge<GNotifier>(), *this);
+}
+
+GNotifier::~GNotifier()
+{
+    GEventLoop::main().unregister_notifier(Badge<GNotifier>(), *this);
+}
+

LibGUI/GNotifier.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <AK/Function.h>
+
+class GNotifier {
+public:
+    enum Event {
+        None        = 0,
+        Read        = 1,
+        Write       = 2,
+        Exceptional = 4,
+    };
+    GNotifier(int fd, unsigned event_mask);
+    ~GNotifier();
+
+    Function<void(GNotifier&)> on_ready_to_read;
+    Function<void(GNotifier&)> on_ready_to_write;
+
+    int fd() const { return m_fd; }
+    unsigned event_mask() const { return m_event_mask; }
+
+private:
+    int m_fd { -1 };
+    unsigned m_event_mask { 0 };
+};

LibGUI/GWidget.cpp

@@ -34,16 +34,11 @@ void GWidget::set_relative_rect(const Rect& rect)
     update();
 }
 
-void GWidget::repaint(const Rect& rect)
-{
-    // FIXME: Implement.
-}
-
 void GWidget::event(GEvent& event)
 {
     switch (event.type()) {
     case GEvent::Paint:
-        m_has_pending_paint_event = false;
+        m_pending_paint_event_rects.clear();
         return handle_paint_event(static_cast<GPaintEvent&>(event));
     case GEvent::Resize:
         return handle_resize_event(static_cast<GResizeEvent&>(event));
@@ -171,14 +166,21 @@ void GWidget::focusout_event(GEvent&)
 }
 
 void GWidget::update()
+{
+    update(rect());
+}
+
+void GWidget::update(const Rect& rect)
 {
     auto* w = window();
     if (!w)
         return;
-    if (m_has_pending_paint_event)
-        return;
-    m_has_pending_paint_event = true;
-    w->update(window_relative_rect());
+    for (auto& pending_rect : m_pending_paint_event_rects) {
+        if (pending_rect.contains(rect))
+            return;
+    }
+    m_pending_paint_event_rects.append(rect);
+    w->update(rect.translated(window_relative_rect().location()));
 }
 
 Rect GWidget::window_relative_rect() const

LibGUI/GWidget.h

@@ -58,7 +58,7 @@ public:
     Size size() const { return m_relative_rect.size(); }
 
     void update();
-    void repaint(const Rect&);
+    void update(const Rect&);
 
     virtual bool accepts_focus() const { return false; }
 
@@ -136,6 +136,7 @@ private:
     SizePolicy m_vertical_size_policy { SizePolicy::Fill };
     Size m_preferred_size;
 
-    bool m_has_pending_paint_event { false };
+    Vector<Rect> m_pending_paint_event_rects;
+
     bool m_fill_with_background_color { true };
 };

LibGUI/GWindow.cpp

@@ -163,13 +163,17 @@ void GWindow::event(GEvent& event)
     }
 
     if (event.is_key_event()) {
-        if (!m_focused_widget)
-            return;
-        return m_focused_widget->event(event);
+        if (m_focused_widget)
+            return m_focused_widget->event(event);
+        if (m_main_widget)
+            return m_main_widget->event(event);
+        return;
     }
 
     if (event.type() == GEvent::WindowBecameActive || event.type() == GEvent::WindowBecameInactive) {
         m_is_active = event.type() == GEvent::WindowBecameActive;
+        if (m_main_widget)
+            m_main_widget->event(event);
         if (m_focused_widget)
             m_focused_widget->update();
         return;
@@ -202,9 +206,18 @@ void GWindow::set_main_widget(GWidget* widget)
     if (m_main_widget == widget)
         return;
     m_main_widget = widget;
-    m_main_widget->set_relative_rect({ 0, 0, width(), height() });
-    if (widget)
-        widget->set_window(this);
+    if (m_main_widget) {
+        auto new_window_rect = rect();
+        if (m_main_widget->horizontal_size_policy() == SizePolicy::Fixed)
+            new_window_rect.set_width(m_main_widget->preferred_size().width());
+        if (m_main_widget->vertical_size_policy() == SizePolicy::Fixed)
+            new_window_rect.set_height(m_main_widget->preferred_size().height());
+        set_rect(new_window_rect);
+        m_main_widget->set_relative_rect({ { }, new_window_rect.size() });
+        m_main_widget->set_window(this);
+        if (m_main_widget->accepts_focus())
+            m_main_widget->set_focus(true);
+    }
     update();
 }
 

LibGUI/GWindow.h

@@ -26,6 +26,7 @@ public:
     int height() const { return rect().height(); }
 
     Rect rect() const;
+    Size size() const { return rect().size(); }
     void set_rect(const Rect&);
     void set_rect(int x, int y, int width, int height) { set_rect({ x, y, width, height }); }
 
@@ -58,6 +59,8 @@ public:
     void set_should_exit_app_on_close(bool b) { m_should_exit_app_on_close = b; }
 
 private:
+    virtual const char* class_name() const override { return "GWindow"; }
+
     RetainPtr<GraphicsBitmap> m_backing;
     int m_window_id { 0 };
     bool m_is_active { false };

LibGUI/Makefile

@@ -13,6 +13,7 @@ LIBGUI_OBJS = \
     GLabel.o \
     GListBox.o \
     GObject.o \
+    GNotifier.o \
     GTextBox.o \
     GScrollBar.o \
     GStatusBar.o \