Tear out or duplicate what's unique for WindowServer from Widgets.

This turned into a huge refactoring that somehow also includes
making locks recursive/reentrant.

30 files changed, 757 insertions, 308 deletions

diff --git a/AK/Lock.h b/AK/Lock.h
index 229c072b39..93fe8f82c6 100644
--- a/AK/Lock.h
+++ b/AK/Lock.h
@@ -2,13 +2,14 @@
 
 #include "Assertions.h"
 #include "Types.h"
-
-#ifdef SERENITY
 #include "i386.h"
 int sched_yield();
-#else
-#include <sched.h>
-typedef int InterruptDisabler;
+
+class Process;
+extern Process* current;
+
+#ifndef KERNEL
+#error This thing is kernel-only right now.
 #endif
 
 //#define DEBUG_LOCKS
@@ -30,70 +31,75 @@ static inline dword CAS(volatile dword* mem, dword newval, dword oldval)
     return ret;
 }
 
-// FIXME: Rename to YieldingLock?
+// FIXME: Rename to YieldingLock? RecursiveLock? Maybe just Lock?
 class SpinLock {
 public:
     SpinLock() { }
     ~SpinLock() { }
 
-    ALWAYS_INLINE void lock(const char* func = nullptr)
-    {
-        (void)func;
-#ifdef DEBUG_LOCKS
-        {
-            InterruptDisabler dis;
-            log_try_lock(func);
-        }
-#endif
-        for (;;) {
-            if (CAS(&m_lock, 1, 0) == 0) {
-#ifdef DEBUG_LOCKS
-                InterruptDisabler dis;
-                log_locked(func);
-#endif
-                return;
-            }
-            sched_yield();
-        }
-    }
+    void lock();
+    void unlock();
 
-    ALWAYS_INLINE void unlock(const char* func = nullptr)
-    {
-        (void)func;
-        // barrier();
-        ASSERT(m_lock);
-        m_lock = 0;
-#ifdef DEBUG_LOCKS
-        InterruptDisabler dis;
-        log_unlocked(func);
-#endif
-    }
-
-    void init()
-    {
-        m_lock = 0;
-    }
+    const Process* holder() const { return m_holder; }
 
 private:
     volatile dword m_lock { 0 };
+    dword m_level { 0 };
+    Process* m_holder { nullptr };
 };
 
 class Locker {
 public:
-    ALWAYS_INLINE explicit Locker(SpinLock& l, const char* func) : m_lock(l), m_func(func) { lock(); }
+    ALWAYS_INLINE explicit Locker(SpinLock& l) : m_lock(l) { lock(); }
     ALWAYS_INLINE ~Locker() { unlock(); }
-    ALWAYS_INLINE void unlock() { m_lock.unlock(m_func); }
-    ALWAYS_INLINE void lock() { m_lock.lock(m_func); }
+    ALWAYS_INLINE void unlock() { m_lock.unlock(); }
+    ALWAYS_INLINE void lock() { m_lock.lock(); }
 
 private:
     SpinLock& m_lock;
-    const char* m_func { nullptr };
 };
 
-#define LOCKER(lock) Locker locker(lock, __FUNCTION__)
+inline void SpinLock::lock()
+{
+    for (;;) {
+        if (CAS(&m_lock, 1, 0) == 0) {
+            if (!m_holder || m_holder == current) {
+                m_holder = current;
+                ++m_level;
+                memory_barrier();
+                m_lock = 0;
+                return;
+            }
+            m_lock = 0;
+        }
+        sched_yield();
+    }
+}
+
+inline void SpinLock::unlock()
+{
+    for (;;) {
+        if (CAS(&m_lock, 1, 0) == 0) {
+            ASSERT(m_holder == current);
+            ASSERT(m_level);
+            --m_level;
+            if (m_level) {
+                memory_barrier();
+                m_lock = 0;
+                return;
+            }
+            m_holder = nullptr;
+            memory_barrier();
+            m_lock = 0;
+            return;
+        }
+        sched_yield();
+    }
+}
+
+#define LOCKER(lock) Locker locker(lock)
 
 }
 
 using AK::SpinLock;
 using AK::Locker;
-
diff --git a/Widgets/GUIEventDevice.cpp b/Kernel/GUIEventDevice.cpp
index 20ba6c917b..20ba6c917b 100644
--- a/Widgets/GUIEventDevice.cpp
+++ b/Kernel/GUIEventDevice.cpp
diff --git a/Widgets/GUIEventDevice.h b/Kernel/GUIEventDevice.h
index e98b208f05..e98b208f05 100644
--- a/Widgets/GUIEventDevice.h
+++ b/Kernel/GUIEventDevice.h
diff --git a/Kernel/Makefile b/Kernel/Makefile
index 149cffa46c..580a921618 100644
--- a/Kernel/Makefile
+++ b/Kernel/Makefile
@@ -30,7 +30,7 @@ KERNEL_OBJS = \
        ELFLoader.o \
        KSyms.o \
        PS2MouseDevice.o \
-       WindowServer.o
+       GUIEventDevice.o
 
 VFS_OBJS = \
     ../VirtualFileSystem/DiskDevice.o \
@@ -46,21 +46,20 @@ VFS_OBJS = \
     ../VirtualFileSystem/FileDescriptor.o \
     ../VirtualFileSystem/SyntheticFileSystem.o
 
-WIDGETS_OBJS = \
-    ../Widgets/Window.o \
-    ../Widgets/Painter.o \
-    ../Widgets/WindowManager.o \
-    ../Widgets/FrameBuffer.o \
-    ../Widgets/GraphicsBitmap.o \
-    ../Widgets/Object.o \
+WINDOWSERVER_OBJS = \
     ../Widgets/Rect.o \
-    ../Widgets/Widget.o \
+    ../Widgets/Painter.o \
     ../Widgets/Font.o \
     ../Widgets/Color.o \
     ../Widgets/CharacterBitmap.o \
-    ../Widgets/EventLoop.o \
-    ../Widgets/AbstractScreen.o \
-    ../Widgets/GUIEventDevice.o \
+    ../Widgets/GraphicsBitmap.o \
+    ../WindowServer/WSEventReceiver.o \
+    ../WindowServer/WSEventLoop.o \
+    ../WindowServer/WSWindow.o \
+    ../WindowServer/WSWindowManager.o \
+    ../WindowServer/WSFrameBuffer.o \
+    ../WindowServer/WSScreen.o \
+    ../WindowServer/main.o
 
 AK_OBJS = \
     ../AK/String.o \
@@ -68,7 +67,7 @@ AK_OBJS = \
     ../AK/StringBuilder.o \
     ../AK/FileSystemPath.o
 
-OBJS = $(KERNEL_OBJS) $(VFS_OBJS) $(AK_OBJS) $(WIDGETS_OBJS)
+OBJS = $(KERNEL_OBJS) $(VFS_OBJS) $(AK_OBJS) $(WINDOWSERVER_OBJS)
 
 NASM = nasm
 KERNEL = kernel
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index 8b7bd457ac..eee7fc70a7 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -18,7 +18,7 @@
 #include "Scheduler.h"
 #include "FIFO.h"
 #include "KSyms.h"
-#include <Widgets/Window.h>
+#include <WindowServer/WSWindow.h>
 #include "MasterPTY.h"
 
 //#define DEBUG_IO
diff --git a/Kernel/Process.h b/Kernel/Process.h
index 4e96a5328c..e79b37fa81 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -19,8 +19,7 @@ class PageDirectory;
 class Region;
 class VMObject;
 class Zone;
-class Window;
-class Widget;
+class WSWindow;
 
 #define COOL_GLOBALS
 #ifdef COOL_GLOBALS
@@ -47,7 +46,7 @@ struct DisplayInfo {
 
 class Process : public InlineLinkedListNode<Process> {
     friend class InlineLinkedListNode<Process>;
-    friend class WindowManager; // FIXME: Make a better API for allocate_region().
+    friend class WSWindowManager; // FIXME: Make a better API for allocate_region().
     friend class GraphicsBitmap; // FIXME: Make a better API for allocate_region().
 public:
     static Process* create_kernel_process(String&& name, void (*entry)());
@@ -353,7 +352,7 @@ private:
 
     RetainPtr<Region> m_display_framebuffer_region;
 
-    HashMap<int, OwnPtr<Window>> m_windows;
+    HashMap<int, OwnPtr<WSWindow>> m_windows;
 
     Vector<GUI_Event> m_gui_events;
     SpinLock m_gui_events_lock;
diff --git a/Kernel/ProcessGUI.cpp b/Kernel/ProcessGUI.cpp
index 6801a9e86b..ff3ff76fc7 100644
--- a/Kernel/ProcessGUI.cpp
+++ b/Kernel/ProcessGUI.cpp
@@ -1,25 +1,22 @@
 #include "Process.h"
 #include "MemoryManager.h"
 #include <LibC/errno_numbers.h>
-#include <Widgets/AbstractScreen.h>
-#include <Widgets/FrameBuffer.h>
-#include <Widgets/EventLoop.h>
 #include <Widgets/Font.h>
-#include <Widgets/Button.h>
-#include <Widgets/Label.h>
-#include <Widgets/Widget.h>
-#include <Widgets/Window.h>
-#include <Widgets/WindowManager.h>
+#include <WindowServer/WSScreen.h>
+#include <WindowServer/WSFrameBuffer.h>
+#include <WindowServer/WSEventLoop.h>
+#include <WindowServer/WSWindow.h>
+#include <WindowServer/WSWindowManager.h>
 
 void Process::initialize_gui_statics()
 {
     Font::initialize();
-    FrameBuffer::initialize();
-    EventLoop::initialize();
-    WindowManager::initialize();
-    AbstractScreen::initialize();
+    WSFrameBuffer::initialize();
+    WSEventLoop::initialize();
+    WSWindowManager::initialize();
+    WSScreen::initialize();
 
-    new EventLoop;
+    new WSEventLoop;
 }
 
 int Process::make_window_id()
@@ -36,7 +33,7 @@ int Process::make_window_id()
 static void wait_for_gui_server()
 {
     // FIXME: Time out after a while and return an error.
-    while (!EventLoop::main().running())
+    while (!WSEventLoop::the().running())
         sleep(10);
 }
 
@@ -53,13 +50,13 @@ int Process::gui$create_window(const GUI_CreateWindowParameters* user_params)
     if (rect.is_empty())
         return -EINVAL;
 
-    ProcessPagingScope scope(EventLoop::main().server_process());
+    ProcessPagingScope scope(WSEventLoop::the().server_process());
 
     int window_id = make_window_id();
     if (!window_id)
         return -ENOMEM;
 
-    auto window = make<Window>(*this, window_id);
+    auto window = make<WSWindow>(*this, window_id);
     if (!window)
         return -ENOMEM;
 
@@ -113,7 +110,6 @@ int Process::gui$invalidate_window(int window_id)
     auto& window = *(*it).value;
     // FIXME: This should queue up a message that the window server process can read.
     //        Poking into its data structures is not good.
-    InterruptDisabler disabler;
-    WindowManager::the().invalidate(window);
+    WSEventLoop::the().post_event(&window, make<WSEvent>(WSEvent::WM_Invalidate));
     return 0;
 }
diff --git a/Kernel/Scheduler.cpp b/Kernel/Scheduler.cpp
index 7bd8ee4d91..f8f546db1c 100644
--- a/Kernel/Scheduler.cpp
+++ b/Kernel/Scheduler.cpp
@@ -133,7 +133,7 @@ bool Scheduler::pick_next()
     for (auto* process = g_processes->head(); process; process = process->next()) {
         //if (process->state() == Process::BlockedWait || process->state() == Process::BlockedSleep)
 //            continue;
-        dbgprintf("% 12s %s(%u) @ %w:%x\n", toString(process->state()), process->name().characters(), process->pid(), process->tss().cs, process->tss().eip);
+        dbgprintf("[K%x] % 12s %s(%u) @ %w:%x\n", process, toString(process->state()), process->name().characters(), process->pid(), process->tss().cs, process->tss().eip);
     }
 #endif
 
diff --git a/Kernel/WindowServer.cpp b/Kernel/WindowServer.cpp
deleted file mode 100644
index 674562ad7f..0000000000
--- a/Kernel/WindowServer.cpp
+++ /dev/null
@@ -1,22 +0,0 @@
-#include "Process.h"
-#include <Widgets/Font.h>
-#include <Widgets/FrameBuffer.h>
-#include <Widgets/WindowManager.h>
-#include <Widgets/EventLoop.h>
-#include <Widgets/Window.h>
-
-void WindowServer_main()
-{
-    auto info = current->get_display_info();
-
-    dbgprintf("Screen is %ux%ux%ubpp\n", info.width, info.height, info.bpp);
-
-    FrameBuffer framebuffer((dword*)info.framebuffer, info.width, info.height);
-
-    WindowManager::the();
-
-    dbgprintf("Entering WindowServer main loop.\n");
-    EventLoop::main().exec();
-
-    ASSERT_NOT_REACHED();
-}
diff --git a/Kernel/i386.h b/Kernel/i386.h
index eae96cbd5c..d48c7b481e 100644
--- a/Kernel/i386.h
+++ b/Kernel/i386.h
@@ -81,6 +81,7 @@ void write_gdt_entry(word selector, Descriptor&);
 
 #define cli() asm volatile("cli")
 #define sti() asm volatile("sti")
+#define memory_barrier() asm volatile ("" ::: "memory")
 
 static inline dword cpu_flags()
 {
diff --git a/Kernel/init.cpp b/Kernel/init.cpp
index 52a942ac8d..1a6ce48bb8 100644
--- a/Kernel/init.cpp
+++ b/Kernel/init.cpp
@@ -15,7 +15,7 @@
 #include <VirtualFileSystem/RandomDevice.h>
 #include <VirtualFileSystem/Ext2FileSystem.h>
 #include <VirtualFileSystem/VirtualFileSystem.h>
-#include <Widgets/GUIEventDevice.h>
+#include "GUIEventDevice.h"
 #include "MemoryManager.h"
 #include "ProcFileSystem.h"
 #include "RTC.h"
diff --git a/Widgets/FrameBuffer.cpp b/Widgets/FrameBuffer.cpp
deleted file mode 100644
index dc93460a07..0000000000
--- a/Widgets/FrameBuffer.cpp
+++ /dev/null
@@ -1,46 +0,0 @@
-#include "FrameBuffer.h"
-#include "GraphicsBitmap.h"
-#include <AK/Assertions.h>
-
-FrameBuffer* s_the;
-
-void FrameBuffer::initialize()
-{
-    s_the = nullptr;
-}
-
-FrameBuffer& FrameBuffer::the()
-{
-    ASSERT(s_the);
-    return *s_the;
-}
-
-FrameBuffer::FrameBuffer(unsigned width, unsigned height)
-    : AbstractScreen(width, height)
-{
-    ASSERT(!s_the);
-    s_the = this;
-}
-
-FrameBuffer::FrameBuffer(RGBA32* data, unsigned width, unsigned height)
-    : AbstractScreen(width, height)
-    , m_data(data)
-{
-    ASSERT(!s_the);
-    s_the = this;
-}
-
-
-FrameBuffer::~FrameBuffer()
-{
-}
-
-void FrameBuffer::show()
-{
-}
-
-RGBA32* FrameBuffer::scanline(int y)
-{
-    unsigned pitch = sizeof(RGBA32) * width();
-    return reinterpret_cast<RGBA32*>(((byte*)m_data) + (y * pitch));
-}
diff --git a/Widgets/FrameBuffer.h b/Widgets/FrameBuffer.h
deleted file mode 100644
index c0758f19a6..0000000000
--- a/Widgets/FrameBuffer.h
+++ /dev/null
@@ -1,25 +0,0 @@
-#pragma once
-
-#include "AbstractScreen.h"
-#include "Color.h"
-
-class GraphicsBitmap;
-
-class FrameBuffer final : public AbstractScreen {
-public:
-    FrameBuffer(unsigned width, unsigned height);
-    FrameBuffer(RGBA32*, unsigned width, unsigned height);
-    virtual ~FrameBuffer() override;
-
-    void show();
-
-    static FrameBuffer& the();
-
-    RGBA32* scanline(int y);
-
-    static void initialize();
-
-private:
-    RGBA32* m_data { nullptr };
-};
-
diff --git a/Widgets/GraphicsBitmap.cpp b/Widgets/GraphicsBitmap.cpp
index 6fc98447f9..3dbc47cf47 100644
--- a/Widgets/GraphicsBitmap.cpp
+++ b/Widgets/GraphicsBitmap.cpp
@@ -1,10 +1,10 @@
 #include "GraphicsBitmap.h"
-#include "EventLoop.h"
 #include <AK/kmalloc.h>
 
 #ifdef KERNEL
-#include "Process.h"
-#include "MemoryManager.h"
+#include <Kernel/Process.h>
+#include <Kernel/MemoryManager.h>
+#include <WindowServer/WSEventLoop.h>
 #endif
 
 #ifdef KERNEL
@@ -24,7 +24,7 @@ GraphicsBitmap::GraphicsBitmap(Process& process, const Size& size)
     m_client_region->commit(process);
 
     {
-        auto& server = EventLoop::main().server_process();
+        auto& server = WSEventLoop::the().server_process();
         ProcessInspectionHandle composer_handle(server);
         m_server_region = server.allocate_region_with_vmo(LinearAddress(), size_in_bytes, move(vmo), 0, "GraphicsBitmap (shared)", true, true);
     }
@@ -50,7 +50,7 @@ GraphicsBitmap::~GraphicsBitmap()
     if (m_client_region)
         m_client_process->deallocate_region(*m_client_region);
     if (m_server_region)
-        EventLoop::main().server_process().deallocate_region(*m_server_region);
+        WSEventLoop::the().server_process().deallocate_region(*m_server_region);
 #endif
     m_data = nullptr;
 }
diff --git a/Widgets/Window.h b/Widgets/Window.h
index 3da05c3c97..1bbe354eb1 100644
--- a/Widgets/Window.h
+++ b/Widgets/Window.h
@@ -28,7 +28,6 @@ public:
     void set_rect_without_repaint(const Rect& rect) { m_rect = rect; }
 
     Point position() const { return m_rect.location(); }
-    void set_position(const Point& position) { set_rect({ position.x(), position.y(), width(), height() }); }
     void set_position_without_repaint(const Point& position) { set_rect_without_repaint({ position.x(), position.y(), width(), height() }); }
 
     virtual void event(Event&) override;
diff --git a/WindowServer/.gitignore b/WindowServer/.gitignore
new file mode 100644
index 0000000000..5761abcfdf
--- /dev/null
+++ b/WindowServer/.gitignore
@@ -0,0 +1 @@
+*.o
diff --git a/WindowServer/WSEvent.h b/WindowServer/WSEvent.h
new file mode 100644
index 0000000000..778dbd29ee
--- /dev/null
+++ b/WindowServer/WSEvent.h
@@ -0,0 +1,151 @@
+#pragma once
+
+#include <Widgets/Point.h>
+#include <Widgets/Rect.h>
+#include <AK/AKString.h>
+#include <AK/Types.h>
+
+static const char* WSEvent_names[] = {
+    "Invalid",
+    "Show",
+    "Hide",
+    "Paint",
+    "MouseMove",
+    "MouseDown",
+    "MouseUp",
+    "KeyDown",
+    "KeyUp",
+    "Timer",
+    "WM_Compose",
+    "WM_Invalidate",
+};
+
+class WSEvent {
+public:
+    enum Type {
+        Invalid = 0,
+        Show,
+        Hide,
+        Paint,
+        MouseMove,
+        MouseDown,
+        MouseUp,
+        KeyDown,
+        KeyUp,
+        Timer,
+        WM_Compose,
+        WM_Invalidate,
+    };
+
+    WSEvent() { }
+    explicit WSEvent(Type type) : m_type(type) { }
+    virtual ~WSEvent() { }
+
+    Type type() const { return m_type; }
+
+    const char* name() const { return WSEvent_names[(unsigned)m_type]; }
+
+    bool isMouseEvent() const { return m_type == MouseMove || m_type == MouseDown || m_type == MouseUp; }
+    bool isKeyEvent() const { return m_type == KeyUp || m_type == KeyDown; }
+    bool isPaintEvent() const { return m_type == Paint; }
+
+private:
+    Type m_type { Invalid };
+};
+
+class PaintEvent final : public WSEvent {
+public:
+    explicit PaintEvent(const Rect& rect = Rect())
+        : WSEvent(WSEvent::Paint)
+        , m_rect(rect)
+    {
+    }
+
+    const Rect& rect() const { return m_rect; }
+private:
+    friend class WSWindowManager;
+    Rect m_rect;
+};
+
+class ShowEvent final : public WSEvent {
+public:
+    ShowEvent()
+        : WSEvent(WSEvent::Show)
+    {
+    }
+};
+
+class HideEvent final : public WSEvent {
+public:
+    HideEvent()
+        : WSEvent(WSEvent::Hide)
+    {
+    }
+};
+
+enum class MouseButton : byte {
+    None = 0,
+    Left,
+    Middle,
+    Right,
+};
+
+enum KeyboardKey {
+    Invalid,
+    LeftArrow,
+    RightArrow,
+    UpArrow,
+    DownArrow,
+    Backspace,
+    Return,
+};
+
+class KeyEvent final : public WSEvent {
+public:
+    KeyEvent(Type type, int key)
+        : WSEvent(type)
+        , m_key(key)
+    {
+    }
+
+    int key() const { return m_key; }
+    bool ctrl() const { return m_ctrl; }
+    bool alt() const { return m_alt; }
+    bool shift() const { return m_shift; }
+    String text() const { return m_text; }
+
+private:
+    friend class WSEventLoop;
+    friend class WSScreen;
+    int m_key { 0 };
+    bool m_ctrl { false };
+    bool m_alt { false };
+    bool m_shift { false };
+    String m_text;
+};
+
+class MouseEvent final : public WSEvent {
+public:
+    MouseEvent(Type type, int x, int y, MouseButton button = MouseButton::None)
+        : WSEvent(type)
+        , m_position(x, y)
+        , m_button(button)
+    {
+    }
+
+    Point position() const { return m_position; }
+    int x() const { return m_position.x(); }
+    int y() const { return m_position.y(); }
+    MouseButton button() const { return m_button; }
+
+private:
+    Point m_position;
+    MouseButton m_button { MouseButton::None };
+};
+
+class TimerEvent final : public WSEvent {
+public:
+    TimerEvent() : WSEvent(WSEvent::Timer) { }
+    ~TimerEvent() { }
+};
+
diff --git a/WindowServer/WSEventLoop.cpp b/WindowServer/WSEventLoop.cpp
new file mode 100644
index 0000000000..a6769a3510
--- /dev/null
+++ b/WindowServer/WSEventLoop.cpp
@@ -0,0 +1,98 @@
+#include "WSEventLoop.h"
+#include "WSEvent.h"
+#include "WSEventReceiver.h"
+#include "WSWindowManager.h"
+#include "WSScreen.h"
+#include "PS2MouseDevice.h"
+#include "Scheduler.h"
+
+//#define WSEVENTLOOP_DEBUG
+
+static WSEventLoop* s_the;
+
+void WSEventLoop::initialize()
+{
+    s_the = nullptr;
+}
+
+WSEventLoop::WSEventLoop()
+{
+    if (!s_the)
+        s_the = this;
+}
+
+WSEventLoop::~WSEventLoop()
+{
+}
+
+WSEventLoop& WSEventLoop::the()
+{
+    ASSERT(s_the);
+    return *s_the;
+}
+
+int WSEventLoop::exec()
+{
+    m_server_process = current;
+    m_running = true;
+    for (;;) {
+        if (m_queued_events.is_empty())
+            waitForEvent();
+        Vector<QueuedEvent> events;
+        {
+            LOCKER(m_lock);
+            events = move(m_queued_events);
+        }
+
+        for (auto& queued_event : events) {
+            auto* receiver = queued_event.receiver;
+            auto& event = *queued_event.event;
+#ifdef WSEVENTLOOP_DEBUG
+            dbgprintf("WSEventLoop: receiver{%p} event %u (%s)\n", receiver, (unsigned)event.type(), event.name());
+#endif
+            if (!receiver) {
+                dbgprintf("WSEvent type %u with no receiver :(\n", event.type());
+                ASSERT_NOT_REACHED();
+                return 1;
+            } else {
+                receiver->event(event);
+            }
+        }
+    }
+}
+
+void WSEventLoop::post_event(WSEventReceiver* receiver, OwnPtr<WSEvent>&& event)
+{
+    //ASSERT_INTERRUPTS_ENABLED();
+    LOCKER(m_lock);
+#ifdef WSEVENTLOOP_DEBUG
+    dbgprintf("WSEventLoop::post_event: {%u} << receiver=%p, event=%p\n", m_queued_events.size(), receiver, event.ptr());
+#endif
+    m_queued_events.append({ receiver, move(event) });
+}
+
+void WSEventLoop::waitForEvent()
+{
+    auto& mouse = PS2MouseDevice::the();
+    auto& screen = WSScreen::the();
+    bool prev_left_button = screen.left_mouse_button_pressed();
+    bool prev_right_button = screen.right_mouse_button_pressed();
+    int dx = 0;
+    int dy = 0;
+    while (mouse.can_read(*m_server_process)) {
+        signed_byte data[3];
+        ssize_t nread = mouse.read(*m_server_process, (byte*)data, 3);
+        ASSERT(nread == 3);
+        bool left_button = data[0] & 1;
+        bool right_button = data[0] & 2;
+        dx += data[1];
+        dy += -data[2];
+        if (left_button != prev_left_button || right_button != prev_right_button || !mouse.can_read(*m_server_process)) {
+            prev_left_button = left_button;
+            prev_right_button = right_button;
+            screen.on_receive_mouse_data(dx, dy, left_button, right_button);
+            dx = 0;
+            dy = 0;
+        }
+    }
+}
diff --git a/WindowServer/WSEventLoop.h b/WindowServer/WSEventLoop.h
new file mode 100644
index 0000000000..d461a6b52a
--- /dev/null
+++ b/WindowServer/WSEventLoop.h
@@ -0,0 +1,40 @@
+#pragma once
+
+#include "WSEvent.h"
+#include <AK/Lock.h>
+#include <AK/OwnPtr.h>
+#include <AK/Vector.h>
+
+class WSEventReceiver;
+class Process;
+
+class WSEventLoop {
+public:
+    WSEventLoop();
+    ~WSEventLoop();
+
+    int exec();
+
+    void post_event(WSEventReceiver* receiver, OwnPtr<WSEvent>&&);
+
+    static WSEventLoop& the();
+
+    static void initialize();
+
+    bool running() const { return m_running; }
+    Process& server_process() { return *m_server_process; }
+
+private:
+    void waitForEvent();
+
+    SpinLock m_lock;
+
+    struct QueuedEvent {
+        WSEventReceiver* receiver { nullptr };
+        OwnPtr<WSEvent> event;
+    };
+    Vector<QueuedEvent> m_queued_events;
+
+    Process* m_server_process { nullptr };
+    bool m_running { false };
+};
diff --git a/WindowServer/WSEventReceiver.cpp b/WindowServer/WSEventReceiver.cpp
new file mode 100644
index 0000000000..74e31e8906
--- /dev/null
+++ b/WindowServer/WSEventReceiver.cpp
@@ -0,0 +1,10 @@
+#include "WSEventReceiver.h"
+#include <AK/Assertions.h>
+
+WSEventReceiver::WSEventReceiver()
+{
+}
+
+WSEventReceiver::~WSEventReceiver()
+{
+}
diff --git a/WindowServer/WSEventReceiver.h b/WindowServer/WSEventReceiver.h
new file mode 100644
index 0000000000..1b81da7c2a
--- /dev/null
+++ b/WindowServer/WSEventReceiver.h
@@ -0,0 +1,13 @@
+#pragma once
+
+#include <AK/Weakable.h>
+
+class WSEvent;
+
+class WSEventReceiver : public Weakable<WSEventReceiver> {
+public:
+    WSEventReceiver();
+    virtual ~WSEventReceiver();
+
+    virtual void event(WSEvent&) = 0;
+};
diff --git a/WindowServer/WSFrameBuffer.cpp b/WindowServer/WSFrameBuffer.cpp
new file mode 100644
index 0000000000..54ca0dc633
--- /dev/null
+++ b/WindowServer/WSFrameBuffer.cpp
@@ -0,0 +1,46 @@
+#include "WSFrameBuffer.h"
+#include <Widgets/GraphicsBitmap.h>
+#include <AK/Assertions.h>
+
+WSFrameBuffer* s_the;
+
+void WSFrameBuffer::initialize()
+{
+    s_the = nullptr;
+}
+
+WSFrameBuffer& WSFrameBuffer::the()
+{
+    ASSERT(s_the);
+    return *s_the;
+}
+
+WSFrameBuffer::WSFrameBuffer(unsigned width, unsigned height)
+    : WSScreen(width, height)
+{
+    ASSERT(!s_the);
+    s_the = this;
+}
+
+WSFrameBuffer::WSFrameBuffer(RGBA32* data, unsigned width, unsigned height)
+    : WSScreen(width, height)
+    , m_data(data)
+{
+    ASSERT(!s_the);
+    s_the = this;
+}
+
+
+WSFrameBuffer::~WSFrameBuffer()
+{
+}
+
+void WSFrameBuffer::show()
+{
+}
+
+RGBA32* WSFrameBuffer::scanline(int y)
+{
+    unsigned pitch = sizeof(RGBA32) * width();
+    return reinterpret_cast<RGBA32*>(((byte*)m_data) + (y * pitch));
+}
diff --git a/WindowServer/WSFrameBuffer.h b/WindowServer/WSFrameBuffer.h
new file mode 100644
index 0000000000..8239fdfd9a
--- /dev/null
+++ b/WindowServer/WSFrameBuffer.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include "WSScreen.h"
+#include <Widgets/Color.h>
+
+class GraphicsBitmap;
+
+class WSFrameBuffer final : public WSScreen {
+public:
+    WSFrameBuffer(unsigned width, unsigned height);
+    WSFrameBuffer(RGBA32*, unsigned width, unsigned height);
+    virtual ~WSFrameBuffer() override;
+
+    void show();
+
+    static WSFrameBuffer& the();
+
+    RGBA32* scanline(int y);
+
+    static void initialize();
+
+private:
+    RGBA32* m_data { nullptr };
+};
+
diff --git a/Widgets/AbstractScreen.cpp b/WindowServer/WSScreen.cpp
index 10993e6363..2276ff6f5d 100644
--- a/Widgets/AbstractScreen.cpp
+++ b/WindowServer/WSScreen.cpp
@@ -1,26 +1,24 @@
-#include "AbstractScreen.h"
-#include "EventLoop.h"
-#include "Event.h"
-#include "Widget.h"
-#include "WindowManager.h"
+#include "WSScreen.h"
+#include "WSEventLoop.h"
+#include "WSEvent.h"
+#include "WSWindowManager.h"
 #include <AK/Assertions.h>
 
-static AbstractScreen* s_the;
+static WSScreen* s_the;
 
-void AbstractScreen::initialize()
+void WSScreen::initialize()
 {
     s_the = nullptr;
 }
 
-AbstractScreen& AbstractScreen::the()
+WSScreen& WSScreen::the()
 {
     ASSERT(s_the);
     return *s_the;
 }
 
-AbstractScreen::AbstractScreen(unsigned width, unsigned height)
-    : Object(nullptr)
-    , m_width(width)
+WSScreen::WSScreen(unsigned width, unsigned height)
+    : m_width(width)
     , m_height(height)
 {
     ASSERT(!s_the);
@@ -31,11 +29,11 @@ AbstractScreen::AbstractScreen(unsigned width, unsigned height)
     Keyboard::the().set_client(this);
 }
 
-AbstractScreen::~AbstractScreen()
+WSScreen::~WSScreen()
 {
 }
 
-void AbstractScreen::on_receive_mouse_data(int dx, int dy, bool left_button, bool right_button)
+void WSScreen::on_receive_mouse_data(int dx, int dy, bool left_button, bool right_button)
 {
     auto prev_location = m_cursor_location;
     m_cursor_location.moveBy(dx, dy);
@@ -45,28 +43,28 @@ void AbstractScreen::on_receive_mouse_data(int dx, int dy, bool left_button, boo
     if (m_cursor_location.y() >= height())
         m_cursor_location.setY(height() - 1);
     if (m_cursor_location != prev_location) {
-        auto event = make<MouseEvent>(Event::MouseMove, m_cursor_location.x(), m_cursor_location.y());
-        EventLoop::main().postEvent(&WindowManager::the(), move(event));
+        auto event = make<MouseEvent>(WSEvent::MouseMove, m_cursor_location.x(), m_cursor_location.y());
+        WSEventLoop::the().post_event(&WSWindowManager::the(), move(event));
     }
     bool prev_left_button = m_left_mouse_button_pressed;
     bool prev_right_button = m_right_mouse_button_pressed;
     m_left_mouse_button_pressed = left_button;
     m_right_mouse_button_pressed = right_button;
     if (prev_left_button != left_button) {
-        auto event = make<MouseEvent>(left_button ? Event::MouseDown : Event::MouseUp, m_cursor_location.x(), m_cursor_location.y(), MouseButton::Left);
-        EventLoop::main().postEvent(&WindowManager::the(), move(event));
+        auto event = make<MouseEvent>(left_button ? WSEvent::MouseDown : WSEvent::MouseUp, m_cursor_location.x(), m_cursor_location.y(), MouseButton::Left);
+        WSEventLoop::the().post_event(&WSWindowManager::the(), move(event));
     }
     if (prev_right_button != right_button) {
-        auto event = make<MouseEvent>(right_button ? Event::MouseDown : Event::MouseUp, m_cursor_location.x(), m_cursor_location.y(), MouseButton::Right);
-        EventLoop::main().postEvent(&WindowManager::the(), move(event));
+        auto event = make<MouseEvent>(right_button ? WSEvent::MouseDown : WSEvent::MouseUp, m_cursor_location.x(), m_cursor_location.y(), MouseButton::Right);
+        WSEventLoop::the().post_event(&WSWindowManager::the(), move(event));
     }
     if (m_cursor_location != prev_location || prev_left_button != left_button)
-        WindowManager::the().draw_cursor();
+        WSWindowManager::the().draw_cursor();
 }
 
-void AbstractScreen::on_key_pressed(Keyboard::Key key)
+void WSScreen::on_key_pressed(Keyboard::Key key)
 {
-    auto event = make<KeyEvent>(Event::KeyDown, 0);
+    auto event = make<KeyEvent>(WSEvent::KeyDown, 0);
     int key_code = 0;
 
     switch (key.character) {
@@ -115,5 +113,5 @@ void AbstractScreen::on_key_pressed(Keyboard::Key key)
     event->m_ctrl = key.ctrl();
     event->m_alt = key.alt();
 
-    EventLoop::main().postEvent(&WindowManager::the(), move(event));
+    WSEventLoop::the().post_event(&WSWindowManager::the(), move(event));
 }
diff --git a/Widgets/AbstractScreen.h b/WindowServer/WSScreen.h
index 444b1efcb3..0967bfcbb1 100644
--- a/Widgets/AbstractScreen.h
+++ b/WindowServer/WSScreen.h
@@ -1,19 +1,17 @@
 #pragma once
 
-#include "Object.h"
-#include "Rect.h"
-#include "Size.h"
-#include "Keyboard.h"
-#include "PS2MouseDevice.h"
+#include <Widgets/Rect.h>
+#include <Widgets/Size.h>
+#include <Kernel/Keyboard.h>
 
-class AbstractScreen : public Object, public KeyboardClient {
+class WSScreen : public KeyboardClient {
 public:
-    virtual ~AbstractScreen();
+    virtual ~WSScreen();
 
     int width() const { return m_width; }
     int height() const { return m_height; }
 
-    static AbstractScreen& the();
+    static WSScreen& the();
 
     Size size() const { return { width(), height() }; }
     Rect rect() const { return { 0, 0, width(), height() }; }
@@ -27,7 +25,7 @@ public:
     void on_receive_mouse_data(int dx, int dy, bool left_button, bool right_button);
 
 protected:
-    AbstractScreen(unsigned width, unsigned height);
+    WSScreen(unsigned width, unsigned height);
 
 private:
     // ^KeyboardClient
diff --git a/WindowServer/WSWindow.cpp b/WindowServer/WSWindow.cpp
new file mode 100644
index 0000000000..72755d0ace
--- /dev/null
+++ b/WindowServer/WSWindow.cpp
@@ -0,0 +1,89 @@
+#include "WSWindow.h"
+#include "WSWindowManager.h"
+#include "WSEvent.h"
+#include "WSEventLoop.h"
+#include "Process.h"
+
+WSWindow::WSWindow(Process& process, int window_id)
+    : m_process(process)
+    , m_window_id(window_id)
+{
+    WSWindowManager::the().addWindow(*this);
+}
+
+WSWindow::~WSWindow()
+{
+    WSWindowManager::the().removeWindow(*this);
+}
+
+void WSWindow::set_title(String&& title)
+{
+    if (m_title == title)
+        return;
+
+    m_title = move(title);
+    WSWindowManager::the().notifyTitleChanged(*this);
+}
+
+void WSWindow::set_rect(const Rect& rect)
+{
+    if (m_rect == rect)
+        return;
+    auto oldRect = m_rect;
+    m_rect = rect;
+    m_backing = GraphicsBitmap::create(m_process, m_rect.size());
+    WSWindowManager::the().notifyRectChanged(*this, oldRect, m_rect);
+}
+
+// FIXME: Just use the same types.
+static GUI_MouseButton to_api(MouseButton button)
+{
+    switch (button) {
+    case MouseButton::None: return GUI_MouseButton::NoButton;
+    case MouseButton::Left: return GUI_MouseButton::Left;
+    case MouseButton::Right: return GUI_MouseButton::Right;
+    case MouseButton::Middle: return GUI_MouseButton::Middle;
+    }
+}
+
+void WSWindow::event(WSEvent& event)
+{
+    GUI_Event gui_event;
+    gui_event.window_id = window_id();
+
+    switch (event.type()) {
+    case WSEvent::Paint:
+        gui_event.type = GUI_Event::Type::Paint;
+        gui_event.paint.rect = static_cast<PaintEvent&>(event).rect();
+        break;
+    case WSEvent::MouseMove:
+        gui_event.type = GUI_Event::Type::MouseMove;
+        gui_event.mouse.position = static_cast<MouseEvent&>(event).position();
+        break;
+    case WSEvent::MouseDown:
+        gui_event.type = GUI_Event::Type::MouseDown;
+        gui_event.mouse.position = static_cast<MouseEvent&>(event).position();
+        gui_event.mouse.button = to_api(static_cast<MouseEvent&>(event).button());
+        break;
+    case WSEvent::MouseUp:
+        gui_event.type = GUI_Event::Type::MouseUp;
+        gui_event.mouse.position = static_cast<MouseEvent&>(event).position();
+        gui_event.mouse.button = to_api(static_cast<MouseEvent&>(event).button());
+        break;
+    case WSEvent::KeyDown:
+        gui_event.type = GUI_Event::Type::KeyDown;
+        gui_event.key.character = static_cast<KeyEvent&>(event).text()[0];
+        break;
+    case WSEvent::WM_Invalidate:
+        WSWindowManager::the().invalidate(*this);
+        return;
+    }
+
+    if (gui_event.type == GUI_Event::Type::Invalid)
+        return;
+
+    {
+        LOCKER(m_process.gui_events_lock());
+        m_process.gui_events().append(move(gui_event));
+    }
+}
diff --git a/WindowServer/WSWindow.h b/WindowServer/WSWindow.h
new file mode 100644
index 0000000000..1e2b54fb2b
--- /dev/null
+++ b/WindowServer/WSWindow.h
@@ -0,0 +1,55 @@
+#pragma once
+
+#include <Widgets/Rect.h>
+#include <Widgets/GraphicsBitmap.h>
+#include <AK/AKString.h>
+#include <AK/InlineLinkedList.h>
+#include "WSEventReceiver.h"
+
+class Process;
+
+class WSWindow final : public WSEventReceiver, public InlineLinkedListNode<WSWindow> {
+public:
+    WSWindow(Process&, int window_id);
+    virtual ~WSWindow() override;
+
+    int window_id() const { return m_window_id; }
+
+    String title() const { return m_title; }
+    void set_title(String&&);
+
+    int x() const { return m_rect.x(); }
+    int y() const { return m_rect.y(); }
+    int width() const { return m_rect.width(); }
+    int height() const { return m_rect.height(); }
+
+    const Rect& rect() const { return m_rect; }
+    void set_rect(const Rect&);
+    void set_rect_without_repaint(const Rect& rect) { m_rect = rect; }
+
+    Point position() const { return m_rect.location(); }
+    void set_position(const Point& position) { set_rect({ position.x(), position.y(), width(), height() }); }
+    void set_position_without_repaint(const Point& position) { set_rect_without_repaint({ position.x(), position.y(), width(), height() }); }
+
+    virtual void event(WSEvent&) override;
+
+    bool is_being_dragged() const { return m_is_being_dragged; }
+    void set_is_being_dragged(bool b) { m_is_being_dragged = b; }
+
+    GraphicsBitmap* backing() { return m_backing.ptr(); }
+
+    // For InlineLinkedList.
+    // FIXME: Maybe make a ListHashSet and then WSWindowManager can just use that.
+    WSWindow* m_next { nullptr };
+    WSWindow* m_prev { nullptr };
+
+private:
+    String m_title;
+    Rect m_rect;
+    bool m_is_being_dragged { false };
+
+    RetainPtr<GraphicsBitmap> m_backing;
+    Process& m_process;
+    int m_window_id { -1 };
+};
+
diff --git a/Widgets/WindowManager.cpp b/WindowServer/WSWindowManager.cpp
index 2b77912277..710eefea55 100644
--- a/Widgets/WindowManager.cpp
+++ b/WindowServer/WSWindowManager.cpp
@@ -1,12 +1,13 @@
-#include "WindowManager.h"
-#include "Painter.h"
-#include "Widget.h"
-#include "Window.h"
-#include "AbstractScreen.h"
-#include "EventLoop.h"
-#include "FrameBuffer.h"
+#include "WSWindowManager.h"
+#include "WSWindow.h"
+#include "WSScreen.h"
+#include "WSEventLoop.h"
+#include "WSFrameBuffer.h"
 #include "Process.h"
 #include "MemoryManager.h"
+#include <Widgets/Painter.h>
+#include <Widgets/CharacterBitmap.h>
+#include <AK/StdLibExtras.h>
 
 //#define DEBUG_FLUSH_YELLOW
 
@@ -50,16 +51,16 @@ static inline Rect outerRectForWindow(const Rect& window)
     return rect;
 }
 
-static WindowManager* s_the_window_manager;
+static WSWindowManager* s_the_window_manager;
 
-WindowManager& WindowManager::the()
+WSWindowManager& WSWindowManager::the()
 {
     if (!s_the_window_manager)
-        s_the_window_manager = new WindowManager;
+        s_the_window_manager = new WSWindowManager;
     return *s_the_window_manager;
 }
 
-void WindowManager::initialize()
+void WSWindowManager::initialize()
 {
     s_the_window_manager = nullptr;
 }
@@ -104,8 +105,8 @@ static const char* cursor_bitmap_outer_ascii = {
     "       ##   "
 };
 
-WindowManager::WindowManager()
-    : m_framebuffer(FrameBuffer::the())
+WSWindowManager::WSWindowManager()
+    : m_framebuffer(WSFrameBuffer::the())
     , m_screen_rect(m_framebuffer.rect())
 {
     auto size = m_screen_rect.size();
@@ -129,11 +130,11 @@ WindowManager::WindowManager()
     compose();
 }
 
-WindowManager::~WindowManager()
+WSWindowManager::~WSWindowManager()
 {
 }
 
-void WindowManager::paintWindowFrame(Window& window)
+void WSWindowManager::paintWindowFrame(WSWindow& window)
 {
     //printf("[WM] paintWindowFrame {%p}, rect: %d,%d %dx%d\n", &window, window.rect().x(), window.rect().y(), window.rect().width(), window.rect().height());
 
@@ -159,7 +160,7 @@ void WindowManager::paintWindowFrame(Window& window)
     m_back_painter->draw_text(titleBarTitleRect, window.title(), Painter::TextAlignment::CenterLeft, titleColor);
 }
 
-void WindowManager::addWindow(Window& window)
+void WSWindowManager::addWindow(WSWindow& window)
 {
     m_windows.set(&window);
     m_windows_in_order.append(&window);
@@ -167,18 +168,13 @@ void WindowManager::addWindow(Window& window)
         setActiveWindow(&window);
 }
 
-void WindowManager::move_to_front(Window& window)
+void WSWindowManager::move_to_front(WSWindow& window)
 {
     m_windows_in_order.remove(&window);
     m_windows_in_order.append(&window);
 }
 
-void WindowManager::did_paint(Window& window)
-{
-    invalidate(window);
-}
-
-void WindowManager::removeWindow(Window& window)
+void WSWindowManager::removeWindow(WSWindow& window)
 {
     if (!m_windows.contains(&window))
         return;
@@ -190,22 +186,24 @@ void WindowManager::removeWindow(Window& window)
         setActiveWindow(*m_windows.begin());
 }
 
-void WindowManager::notifyTitleChanged(Window& window)
+void WSWindowManager::notifyTitleChanged(WSWindow& window)
 {
-    printf("[WM] Window{%p} title set to '%s'\n", &window, window.title().characters());
+    printf("[WM] WSWindow{%p} title set to '%s'\n", &window, window.title().characters());
 }
 
-void WindowManager::notifyRectChanged(Window& window, const Rect& old_rect, const Rect& new_rect)
+void WSWindowManager::notifyRectChanged(WSWindow& window, const Rect& old_rect, const Rect& new_rect)
 {
-    printf("[WM] Window %p rect changed (%d,%d %dx%d) -> (%d,%d %dx%d)\n", &window, old_rect.x(), old_rect.y(), old_rect.width(), old_rect.height(), new_rect.x(), new_rect.y(), new_rect.width(), new_rect.height());
+    printf("[WM] WSWindow %p rect changed (%d,%d %dx%d) -> (%d,%d %dx%d)\n", &window, old_rect.x(), old_rect.y(), old_rect.width(), old_rect.height(), new_rect.x(), new_rect.y(), new_rect.width(), new_rect.height());
+    ASSERT_INTERRUPTS_ENABLED();
+    LOCKER(m_lock);
     invalidate(outerRectForWindow(old_rect));
     invalidate(outerRectForWindow(new_rect));
 }
 
-void WindowManager::handleTitleBarMouseEvent(Window& window, MouseEvent& event)
+void WSWindowManager::handleTitleBarMouseEvent(WSWindow& window, MouseEvent& event)
 {
-    if (event.type() == Event::MouseDown && event.button() == MouseButton::Left) {
-        printf("[WM] Begin dragging Window{%p}\n", &window);
+    if (event.type() == WSEvent::MouseDown && event.button() == MouseButton::Left) {
+        printf("[WM] Begin dragging WSWindow{%p}\n", &window);
         m_dragWindow = window.makeWeakPtr();;
         m_dragOrigin = event.position();
         m_dragWindowOrigin = window.position();
@@ -215,11 +213,11 @@ void WindowManager::handleTitleBarMouseEvent(Window& window, MouseEvent& event)
     }
 }
 
-void WindowManager::processMouseEvent(MouseEvent& event)
+void WSWindowManager::processMouseEvent(MouseEvent& event)
 {
-    if (event.type() == Event::MouseUp && event.button() == MouseButton::Left) {
+    if (event.type() == WSEvent::MouseUp && event.button() == MouseButton::Left) {
         if (m_dragWindow) {
-            printf("[WM] Finish dragging Window{%p}\n", m_dragWindow.ptr());
+            printf("[WM] Finish dragging WSWindow{%p}\n", m_dragWindow.ptr());
             invalidate(m_dragStartRect);
             invalidate(*m_dragWindow);
             m_dragWindow->set_is_being_dragged(false);
@@ -229,7 +227,7 @@ void WindowManager::processMouseEvent(MouseEvent& event)
         }
     }
 
-    if (event.type() == Event::MouseMove) {
+    if (event.type() == WSEvent::MouseMove) {
         if (m_dragWindow) {
             auto old_window_rect = m_dragWindow->rect();
             Point pos = m_dragWindowOrigin;
@@ -244,7 +242,7 @@ void WindowManager::processMouseEvent(MouseEvent& event)
 
     for (auto* window = m_windows_in_order.tail(); window; window = window->prev()) {
         if (titleBarRectForWindow(window->rect()).contains(event.position())) {
-            if (event.type() == Event::MouseDown) {
+            if (event.type() == WSEvent::MouseDown) {
                 move_to_front(*window);
                 setActiveWindow(window);
             }
@@ -253,7 +251,7 @@ void WindowManager::processMouseEvent(MouseEvent& event)
         }
 
         if (window->rect().contains(event.position())) {
-            if (event.type() == Event::MouseDown) {
+            if (event.type() == WSEvent::MouseDown) {
                 move_to_front(*window);
                 setActiveWindow(window);
             }
@@ -265,7 +263,7 @@ void WindowManager::processMouseEvent(MouseEvent& event)
     }
 }
 
-void WindowManager::compose()
+void WSWindowManager::compose()
 {
     auto invalidated_rects = move(m_invalidated_rects);
     printf("[WM] compose #%u (%u rects)\n", ++m_recompose_count, invalidated_rects.size());
@@ -297,8 +295,10 @@ void WindowManager::compose()
     draw_cursor();
 }
 
-void WindowManager::draw_cursor()
+void WSWindowManager::draw_cursor()
 {
+    ASSERT_INTERRUPTS_ENABLED();
+    LOCKER(m_lock);
     auto cursor_location = m_framebuffer.cursor_location();
     Rect cursor_rect { cursor_location.x(), cursor_location.y(), (int)m_cursor_bitmap_inner->width(), (int)m_cursor_bitmap_inner->height() };
     flush(m_last_cursor_rect.united(cursor_rect));
@@ -311,8 +311,10 @@ void WindowManager::draw_cursor()
     m_last_cursor_rect = cursor_rect;
 }
 
-void WindowManager::event(Event& event)
+void WSWindowManager::event(WSEvent& event)
 {
+    ASSERT_INTERRUPTS_ENABLED();
+    LOCKER(m_lock);
     if (event.isMouseEvent())
         return processMouseEvent(static_cast<MouseEvent&>(event));
 
@@ -320,46 +322,35 @@ void WindowManager::event(Event& event)
         // FIXME: This is a good place to hook key events globally. :)
         if (m_activeWindow)
             return m_activeWindow->event(event);
-        return Object::event(event);
+        return;
     }
 
-    if (event.type() == Event::WM_Compose) {
+    if (event.type() == WSEvent::WM_Compose) {
         m_pending_compose_event = false;
         compose();
         return;
     }
-
-    return Object::event(event);
 }
 
-void WindowManager::setActiveWindow(Window* window)
+void WSWindowManager::setActiveWindow(WSWindow* window)
 {
     if (window == m_activeWindow.ptr())
         return;
 
-    if (auto* previously_active_window = m_activeWindow.ptr()) {
+    if (auto* previously_active_window = m_activeWindow.ptr())
         invalidate(*previously_active_window);
-        EventLoop::main().postEvent(previously_active_window, make<Event>(Event::WindowBecameInactive));
-    }
     m_activeWindow = window->makeWeakPtr();
-    if (m_activeWindow) {
+    if (m_activeWindow)
         invalidate(*m_activeWindow);
-        EventLoop::main().postEvent(m_activeWindow.ptr(), make<Event>(Event::WindowBecameActive));
-    }
-}
-
-bool WindowManager::isVisible(Window& window) const
-{
-    return m_windows.contains(&window);
 }
 
-void WindowManager::invalidate()
+void WSWindowManager::invalidate()
 {
     m_invalidated_rects.clear_with_capacity();
     m_invalidated_rects.append(m_screen_rect);
 }
 
-void WindowManager::invalidate(const Rect& a_rect)
+void WSWindowManager::invalidate(const Rect& a_rect)
 {
     auto rect = Rect::intersection(a_rect, m_screen_rect);
     if (rect.is_empty())
@@ -379,17 +370,20 @@ void WindowManager::invalidate(const Rect& a_rect)
     m_invalidated_rects.append(rect);
 
     if (!m_pending_compose_event) {
-        EventLoop::main().postEvent(this, make<Event>(Event::WM_Compose));
+        ASSERT_INTERRUPTS_ENABLED();
+        WSEventLoop::the().post_event(this, make<WSEvent>(WSEvent::WM_Compose));
         m_pending_compose_event = true;
     }
 }
 
-void WindowManager::invalidate(const Window& window)
+void WSWindowManager::invalidate(const WSWindow& window)
 {
+    ASSERT_INTERRUPTS_ENABLED();
+    LOCKER(m_lock);
     invalidate(outerRectForWindow(window.rect()));
 }
 
-void WindowManager::flush(const Rect& a_rect)
+void WSWindowManager::flush(const Rect& a_rect)
 {
     auto rect = Rect::intersection(a_rect, m_screen_rect);
 
diff --git a/Widgets/WindowManager.h b/WindowServer/WSWindowManager.h
index a5277861f4..b6bf211ac2 100644
--- a/Widgets/WindowManager.h
+++ b/WindowServer/WSWindowManager.h
@@ -1,61 +1,58 @@
 #pragma once
 
-#include "Object.h"
-#include "Rect.h"
-#include "Color.h"
-#include "Painter.h"
+#include <Widgets/Rect.h>
+#include <Widgets/Color.h>
+#include <Widgets/Painter.h>
 #include <AK/HashTable.h>
 #include <AK/InlineLinkedList.h>
 #include <AK/WeakPtr.h>
+#include <AK/Lock.h>
+#include "WSEventReceiver.h"
 
-class FrameBuffer;
+class WSFrameBuffer;
 class MouseEvent;
 class PaintEvent;
-class Widget;
-class Window;
+class WSWindow;
 class CharacterBitmap;
 class GraphicsBitmap;
 
-class WindowManager : public Object {
+class WSWindowManager : public WSEventReceiver {
 public:
-    static WindowManager& the(); 
-    void addWindow(Window&);
-    void removeWindow(Window&);
+    static WSWindowManager& the();
+    void addWindow(WSWindow&);
+    void removeWindow(WSWindow&);
 
-    void notifyTitleChanged(Window&);
-    void notifyRectChanged(Window&, const Rect& oldRect, const Rect& newRect);
+    void notifyTitleChanged(WSWindow&);
+    void notifyRectChanged(WSWindow&, const Rect& oldRect, const Rect& newRect);
 
-    Window* activeWindow() { return m_activeWindow.ptr(); }
-    void setActiveWindow(Window*);
+    WSWindow* activeWindow() { return m_activeWindow.ptr(); }
 
-    bool isVisible(Window&) const;
-
-    void did_paint(Window&);
-
-    void move_to_front(Window&);
+    void move_to_front(WSWindow&);
 
     static void initialize();
 
     void draw_cursor();
 
-    void invalidate(const Window&);
+    void invalidate(const WSWindow&);
     void invalidate(const Rect&);
     void invalidate();
     void flush(const Rect&);
 
 private:
-    WindowManager();
-    virtual ~WindowManager() override;
+    WSWindowManager();
+    virtual ~WSWindowManager() override;
 
     void processMouseEvent(MouseEvent&);
-    void handleTitleBarMouseEvent(Window&, MouseEvent&);
+    void handleTitleBarMouseEvent(WSWindow&, MouseEvent&);
+
+    void setActiveWindow(WSWindow*);
     
-    virtual void event(Event&) override;
+    virtual void event(WSEvent&) override;
 
     void compose();
-    void paintWindowFrame(Window&);
+    void paintWindowFrame(WSWindow&);
 
-    FrameBuffer& m_framebuffer;
+    WSFrameBuffer& m_framebuffer;
     Rect m_screen_rect;
 
     Color m_activeWindowBorderColor;
@@ -64,12 +61,12 @@ private:
     Color m_inactiveWindowBorderColor;
     Color m_inactiveWindowTitleColor;
 
-    HashTable<Window*> m_windows;
-    InlineLinkedList<Window> m_windows_in_order;
+    HashTable<WSWindow*> m_windows;
+    InlineLinkedList<WSWindow> m_windows_in_order;
 
-    WeakPtr<Window> m_activeWindow;
+    WeakPtr<WSWindow> m_activeWindow;
 
-    WeakPtr<Window> m_dragWindow;
+    WeakPtr<WSWindow> m_dragWindow;
 
     Point m_dragOrigin;
     Point m_dragWindowOrigin;
@@ -93,4 +90,6 @@ private:
 
     OwnPtr<Painter> m_back_painter;
     OwnPtr<Painter> m_front_painter;
+
+    mutable SpinLock m_lock;
 };
diff --git a/WindowServer/main.cpp b/WindowServer/main.cpp
new file mode 100644
index 0000000000..827f8291e4
--- /dev/null
+++ b/WindowServer/main.cpp
@@ -0,0 +1,25 @@
+#include "Process.h"
+#include <Widgets/Font.h>
+#include <WindowServer/WSFrameBuffer.h>
+#include <WindowServer/WSWindowManager.h>
+#include <WindowServer/WSEventLoop.h>
+#include <WindowServer/WSWindow.h>
+
+// NOTE: This actually runs as a kernel process.
+//       I'd like to change this eventually.
+
+void WindowServer_main()
+{
+    auto info = current->get_display_info();
+
+    dbgprintf("Screen is %ux%ux%ubpp\n", info.width, info.height, info.bpp);
+
+    WSFrameBuffer framebuffer((dword*)info.framebuffer, info.width, info.height);
+
+    WSWindowManager::the();
+
+    dbgprintf("Entering WindowServer main loop.\n");
+    WSEventLoop::the().exec();
+
+    ASSERT_NOT_REACHED();
+}