Services: Move Taskbar and SystemMenu from Applications to Services

9 files changed, 653 insertions, 0 deletions

diff --git a/Services/Taskbar/Makefile b/Services/Taskbar/Makefile
new file mode 100644
index 0000000000..f40e2a3032
--- /dev/null
+++ b/Services/Taskbar/Makefile
@@ -0,0 +1,11 @@
+OBJS = \
+    TaskbarWindow.o \
+    TaskbarButton.o \
+    WindowList.o \
+    main.o
+
+PROGRAM = Taskbar
+
+LIB_DEPS = GUI Gfx IPC Core
+
+include ../../Makefile.common
diff --git a/Services/Taskbar/TaskbarButton.cpp b/Services/Taskbar/TaskbarButton.cpp
new file mode 100644
index 0000000000..68e0441211
--- /dev/null
+++ b/Services/Taskbar/TaskbarButton.cpp
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "TaskbarButton.h"
+#include <LibGUI/Action.h>
+#include <LibGUI/WindowServerConnection.h>
+
+TaskbarButton::TaskbarButton(const WindowIdentifier& identifier)
+    : m_identifier(identifier)
+{
+}
+
+TaskbarButton::~TaskbarButton()
+{
+}
+
+void TaskbarButton::context_menu_event(GUI::ContextMenuEvent&)
+{
+    GUI::WindowServerConnection::the().post_message(Messages::WindowServer::WM_PopupWindowMenu(m_identifier.client_id(), m_identifier.window_id(), screen_relative_rect().location()));
+}
+
+void TaskbarButton::resize_event(GUI::ResizeEvent& event)
+{
+    GUI::WindowServerConnection::the().post_message(
+        Messages::WindowServer::WM_SetWindowTaskbarRect(
+            m_identifier.client_id(),
+            m_identifier.window_id(),
+            screen_relative_rect()));
+    return GUI::Button::resize_event(event);
+}
diff --git a/Services/Taskbar/TaskbarButton.h b/Services/Taskbar/TaskbarButton.h
new file mode 100644
index 0000000000..d8852cfcc1
--- /dev/null
+++ b/Services/Taskbar/TaskbarButton.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "WindowIdentifier.h"
+#include <LibGUI/Button.h>
+
+class TaskbarButton final : public GUI::Button {
+    C_OBJECT(TaskbarButton)
+public:
+    virtual ~TaskbarButton() override;
+
+private:
+    explicit TaskbarButton(const WindowIdentifier&);
+
+    virtual void context_menu_event(GUI::ContextMenuEvent&) override;
+    virtual void resize_event(GUI::ResizeEvent&) override;
+
+    WindowIdentifier m_identifier;
+};
diff --git a/Services/Taskbar/TaskbarWindow.cpp b/Services/Taskbar/TaskbarWindow.cpp
new file mode 100644
index 0000000000..7e2638ebd0
--- /dev/null
+++ b/Services/Taskbar/TaskbarWindow.cpp
@@ -0,0 +1,221 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "TaskbarWindow.h"
+#include "TaskbarButton.h"
+#include <AK/SharedBuffer.h>
+#include <LibCore/ConfigFile.h>
+#include <LibCore/StandardPaths.h>
+#include <LibGUI/BoxLayout.h>
+#include <LibGUI/Button.h>
+#include <LibGUI/Desktop.h>
+#include <LibGUI/Frame.h>
+#include <LibGUI/Window.h>
+#include <stdio.h>
+
+//#define EVENT_DEBUG
+
+TaskbarWindow::TaskbarWindow()
+{
+    set_window_type(GUI::WindowType::Taskbar);
+    set_title("Taskbar");
+
+    on_screen_rect_change(GUI::Desktop::the().rect());
+
+    GUI::Desktop::the().on_rect_change = [this](const Gfx::Rect& rect) { on_screen_rect_change(rect); };
+
+    auto& widget = set_main_widget<GUI::Frame>();
+    widget.set_fill_with_background_color(true);
+    widget.set_layout<GUI::HorizontalBoxLayout>();
+    widget.layout()->set_margins({ 3, 2, 3, 2 });
+    widget.layout()->set_spacing(3);
+    widget.set_frame_thickness(1);
+    widget.set_frame_shape(Gfx::FrameShape::Panel);
+    widget.set_frame_shadow(Gfx::FrameShadow::Raised);
+
+    m_default_icon = Gfx::Bitmap::load_from_file("/res/icons/16x16/window.png");
+
+    WindowList::the().aid_create_button = [this](auto& identifier) {
+        return create_button(identifier);
+    };
+
+    create_quick_launch_bar();
+}
+
+TaskbarWindow::~TaskbarWindow()
+{
+}
+
+void TaskbarWindow::create_quick_launch_bar()
+{
+    auto& quick_launch_bar = main_widget()->add<GUI::Frame>();
+    quick_launch_bar.set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
+    quick_launch_bar.set_layout<GUI::HorizontalBoxLayout>();
+    quick_launch_bar.layout()->set_spacing(3);
+    quick_launch_bar.layout()->set_margins({ 3, 0, 3, 0 });
+    quick_launch_bar.set_frame_thickness(0);
+
+    int total_width = 6;
+    bool first = true;
+
+    auto config = Core::ConfigFile::get_for_app("Taskbar");
+    constexpr const char* quick_launch = "QuickLaunch";
+
+    // FIXME: Core::ConfigFile does not keep the order of the entries.
+    for (auto& name : config->keys(quick_launch)) {
+        auto af_name = config->read_entry(quick_launch, name);
+        ASSERT(!af_name.is_null());
+        auto af_path = String::format("/res/apps/%s", af_name.characters());
+        auto af = Core::ConfigFile::open(af_path);
+        auto app_executable = af->read_entry("App", "Executable");
+        auto app_icon_path = af->read_entry("Icons", "16x16");
+
+        auto& button = quick_launch_bar.add<GUI::Button>();
+        button.set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
+        button.set_preferred_size(22, 22);
+        button.set_button_style(Gfx::ButtonStyle::CoolBar);
+
+        button.set_icon(Gfx::Bitmap::load_from_file(app_icon_path));
+        button.set_tooltip(name);
+        button.on_click = [app_executable] {
+            pid_t pid = fork();
+            if (pid < 0) {
+                perror("fork");
+            } else if (pid == 0) {
+                if (chdir(Core::StandardPaths::home_directory().characters()) < 0) {
+                    perror("chdir");
+                    exit(1);
+                }
+                execl(app_executable.characters(), app_executable.characters(), nullptr);
+                perror("execl");
+                ASSERT_NOT_REACHED();
+            }
+        };
+
+        if (!first)
+            total_width += 3;
+        first = false;
+        total_width += 22;
+    }
+
+    quick_launch_bar.set_preferred_size(total_width, 22);
+}
+
+void TaskbarWindow::on_screen_rect_change(const Gfx::Rect& rect)
+{
+    Gfx::Rect new_rect { rect.x(), rect.bottom() - taskbar_height() + 1, rect.width(), taskbar_height() };
+    set_rect(new_rect);
+}
+
+NonnullRefPtr<GUI::Button> TaskbarWindow::create_button(const WindowIdentifier& identifier)
+{
+    auto& button = main_widget()->add<TaskbarButton>(identifier);
+    button.set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
+    button.set_preferred_size(140, 22);
+    button.set_text_alignment(Gfx::TextAlignment::CenterLeft);
+    button.set_icon(*m_default_icon);
+    return button;
+}
+
+static bool should_include_window(GUI::WindowType window_type, bool is_frameless)
+{
+    return window_type == GUI::WindowType::Normal && !is_frameless;
+}
+
+void TaskbarWindow::wm_event(GUI::WMEvent& event)
+{
+    WindowIdentifier identifier { event.client_id(), event.window_id() };
+    switch (event.type()) {
+    case GUI::Event::WM_WindowRemoved: {
+#ifdef EVENT_DEBUG
+        auto& removed_event = static_cast<GUI::WMWindowRemovedEvent&>(event);
+        dbgprintf("WM_WindowRemoved: client_id=%d, window_id=%d\n",
+            removed_event.client_id(),
+            removed_event.window_id());
+#endif
+        WindowList::the().remove_window(identifier);
+        update();
+        break;
+    }
+    case GUI::Event::WM_WindowRectChanged: {
+#ifdef EVENT_DEBUG
+        auto& changed_event = static_cast<GUI::WMWindowRectChangedEvent&>(event);
+        dbgprintf("WM_WindowRectChanged: client_id=%d, window_id=%d, rect=%s\n",
+            changed_event.client_id(),
+            changed_event.window_id(),
+            changed_event.rect().to_string().characters());
+#endif
+        break;
+    }
+
+    case GUI::Event::WM_WindowIconBitmapChanged: {
+        auto& changed_event = static_cast<GUI::WMWindowIconBitmapChangedEvent&>(event);
+#ifdef EVENT_DEBUG
+        dbgprintf("WM_WindowIconBitmapChanged: client_id=%d, window_id=%d, icon_buffer_id=%d\n",
+            changed_event.client_id(),
+            changed_event.window_id(),
+            changed_event.icon_buffer_id());
+#endif
+        if (auto* window = WindowList::the().window(identifier)) {
+            auto buffer = SharedBuffer::create_from_shbuf_id(changed_event.icon_buffer_id());
+            ASSERT(buffer);
+            window->button()->set_icon(Gfx::Bitmap::create_with_shared_buffer(Gfx::BitmapFormat::RGBA32, *buffer, changed_event.icon_size()));
+        }
+        break;
+    }
+
+    case GUI::Event::WM_WindowStateChanged: {
+        auto& changed_event = static_cast<GUI::WMWindowStateChangedEvent&>(event);
+#ifdef EVENT_DEBUG
+        dbgprintf("WM_WindowStateChanged: client_id=%d, window_id=%d, title=%s, rect=%s, is_active=%u, is_minimized=%u\n",
+            changed_event.client_id(),
+            changed_event.window_id(),
+            changed_event.title().characters(),
+            changed_event.rect().to_string().characters(),
+            changed_event.is_active(),
+            changed_event.is_minimized());
+#endif
+        if (!should_include_window(changed_event.window_type(), changed_event.is_frameless()))
+            break;
+        auto& window = WindowList::the().ensure_window(identifier);
+        window.set_title(changed_event.title());
+        window.set_rect(changed_event.rect());
+        window.set_active(changed_event.is_active());
+        window.set_minimized(changed_event.is_minimized());
+        if (window.is_minimized()) {
+            window.button()->set_foreground_color(Color::DarkGray);
+            window.button()->set_text(String::format("[%s]", changed_event.title().characters()));
+        } else {
+            window.button()->set_foreground_color(Color::Black);
+            window.button()->set_text(changed_event.title());
+        }
+        window.button()->set_checked(changed_event.is_active());
+        break;
+    }
+    default:
+        break;
+    }
+}
diff --git a/Services/Taskbar/TaskbarWindow.h b/Services/Taskbar/TaskbarWindow.h
new file mode 100644
index 0000000000..5825012439
--- /dev/null
+++ b/Services/Taskbar/TaskbarWindow.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "WindowList.h"
+#include <LibGUI/Widget.h>
+#include <LibGUI/Window.h>
+
+class TaskbarWindow final : public GUI::Window {
+    C_OBJECT(TaskbarWindow)
+public:
+    TaskbarWindow();
+    virtual ~TaskbarWindow() override;
+
+    int taskbar_height() const { return 28; }
+
+private:
+    void create_quick_launch_bar();
+    void on_screen_rect_change(const Gfx::Rect&);
+    NonnullRefPtr<GUI::Button> create_button(const WindowIdentifier&);
+
+    virtual void wm_event(GUI::WMEvent&) override;
+
+    RefPtr<Gfx::Bitmap> m_default_icon;
+};
diff --git a/Services/Taskbar/WindowIdentifier.h b/Services/Taskbar/WindowIdentifier.h
new file mode 100644
index 0000000000..cdb645449a
--- /dev/null
+++ b/Services/Taskbar/WindowIdentifier.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Traits.h>
+
+class WindowIdentifier {
+public:
+    WindowIdentifier(int client_id, int window_id)
+        : m_client_id(client_id)
+        , m_window_id(window_id)
+    {
+    }
+
+    int client_id() const { return m_client_id; }
+    int window_id() const { return m_window_id; }
+
+    bool operator==(const WindowIdentifier& other) const
+    {
+        return m_client_id == other.m_client_id && m_window_id == other.m_window_id;
+    }
+
+private:
+    int m_client_id { -1 };
+    int m_window_id { -1 };
+};
+
+namespace AK {
+template<>
+struct Traits<WindowIdentifier> : public GenericTraits<WindowIdentifier> {
+    static unsigned hash(const WindowIdentifier& w) { return pair_int_hash(w.client_id(), w.window_id()); }
+};
+}
diff --git a/Services/Taskbar/WindowList.cpp b/Services/Taskbar/WindowList.cpp
new file mode 100644
index 0000000000..948dcb0452
--- /dev/null
+++ b/Services/Taskbar/WindowList.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "WindowList.h"
+#include <LibGUI/WindowServerConnection.h>
+
+WindowList& WindowList::the()
+{
+    static WindowList* s_the;
+    if (!s_the)
+        s_the = new WindowList;
+    return *s_the;
+}
+
+Window* WindowList::window(const WindowIdentifier& identifier)
+{
+    auto it = m_windows.find(identifier);
+    if (it != m_windows.end())
+        return it->value;
+    return nullptr;
+}
+
+Window& WindowList::ensure_window(const WindowIdentifier& identifier)
+{
+    auto it = m_windows.find(identifier);
+    if (it != m_windows.end())
+        return *it->value;
+    auto window = make<Window>(identifier);
+    window->set_button(aid_create_button(identifier));
+    window->button()->on_click = [window = window.ptr(), identifier] {
+        if (window->is_minimized() || !window->is_active()) {
+            GUI::WindowServerConnection::the().post_message(Messages::WindowServer::WM_SetActiveWindow(identifier.client_id(), identifier.window_id()));
+        } else {
+            GUI::WindowServerConnection::the().post_message(Messages::WindowServer::WM_SetWindowMinimized(identifier.client_id(), identifier.window_id(), true));
+        }
+    };
+    auto& window_ref = *window;
+    m_windows.set(identifier, move(window));
+    return window_ref;
+}
+
+void WindowList::remove_window(const WindowIdentifier& identifier)
+{
+    m_windows.remove(identifier);
+}
diff --git a/Services/Taskbar/WindowList.h b/Services/Taskbar/WindowList.h
new file mode 100644
index 0000000000..90d842c3f4
--- /dev/null
+++ b/Services/Taskbar/WindowList.h
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "WindowIdentifier.h"
+#include <AK/String.h>
+#include <AK/HashMap.h>
+#include <LibGUI/Button.h>
+#include <LibGfx/Rect.h>
+
+class Window {
+public:
+    explicit Window(const WindowIdentifier& identifier)
+        : m_identifier(identifier)
+    {
+    }
+
+    ~Window()
+    {
+        if (m_button)
+            m_button->remove_from_parent();
+    }
+
+    WindowIdentifier identifier() const { return m_identifier; }
+
+    String title() const { return m_title; }
+    void set_title(const String& title) { m_title = title; }
+
+    Gfx::Rect rect() const { return m_rect; }
+    void set_rect(const Gfx::Rect& rect) { m_rect = rect; }
+
+    GUI::Button* button() { return m_button; }
+    void set_button(GUI::Button* button) { m_button = button; }
+
+    void set_active(bool active) { m_active = active; }
+    bool is_active() const { return m_active; }
+
+    void set_minimized(bool minimized) { m_minimized = minimized; }
+    bool is_minimized() const { return m_minimized; }
+
+    const Gfx::Bitmap* icon() const { return m_icon.ptr(); }
+
+private:
+    WindowIdentifier m_identifier;
+    String m_title;
+    Gfx::Rect m_rect;
+    RefPtr<GUI::Button> m_button;
+    RefPtr<Gfx::Bitmap> m_icon;
+    bool m_active { false };
+    bool m_minimized { false };
+};
+
+class WindowList {
+public:
+    static WindowList& the();
+
+    template<typename Callback>
+    void for_each_window(Callback callback)
+    {
+        for (auto& it : m_windows)
+            callback(*it.value);
+    }
+
+    Window* window(const WindowIdentifier&);
+    Window& ensure_window(const WindowIdentifier&);
+    void remove_window(const WindowIdentifier&);
+
+    Function<NonnullRefPtr<GUI::Button>(const WindowIdentifier&)> aid_create_button;
+
+private:
+    HashMap<WindowIdentifier, NonnullOwnPtr<Window>> m_windows;
+};
diff --git a/Services/Taskbar/main.cpp b/Services/Taskbar/main.cpp
new file mode 100644
index 0000000000..33b96cb465
--- /dev/null
+++ b/Services/Taskbar/main.cpp
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "TaskbarWindow.h"
+#include <LibGUI/Application.h>
+#include <signal.h>
+#include <stdio.h>
+#include <sys/wait.h>
+
+int main(int argc, char** argv)
+{
+    if (pledge("stdio shared_buffer accept proc exec rpath unix cpath fattr", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    GUI::Application app(argc, argv);
+
+    if (pledge("stdio shared_buffer accept proc exec rpath", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    TaskbarWindow window;
+    window.show();
+
+    signal(SIGCHLD, [](int signo) {
+        (void)signo;
+        wait(nullptr);
+    });
+
+    return app.exec();
+}