SystemMenu: Add a separate program to host the system menu

This will allow us to run the system menu as any user. It will also
enable further lockdown of the WindowServer process since it should no
longer need to pledge proc and exec. :^)

Note that this program is not finished yet.

Work towards #1231.

Applications/SystemMenu/Makefile

@@ -0,0 +1,8 @@
+OBJS = \
+    main.o
+
+PROGRAM = SystemMenu
+
+LIB_DEPS = GUI Gfx IPC Core
+
+include ../../Makefile.common

Applications/SystemMenu/main.cpp

@@ -0,0 +1,188 @@
+/*
+ * Copyright (c) 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 <AK/FileSystemPath.h>
+#include <AK/QuickSort.h>
+#include <LibCore/ConfigFile.h>
+#include <LibCore/DirIterator.h>
+#include <LibGUI/Action.h>
+#include <LibGUI/Application.h>
+#include <LibGUI/Desktop.h>
+#include <LibGUI/Menu.h>
+#include <LibGUI/MenuBar.h>
+#include <LibGUI/MessageBox.h>
+#include <LibGfx/Bitmap.h>
+#include <stdio.h>
+#include <sys/utsname.h>
+#include <unistd.h>
+
+struct AppMetadata {
+    String executable;
+    String name;
+    String icon_path;
+    String category;
+};
+Vector<AppMetadata> g_apps;
+
+HashMap<String, NonnullRefPtr<GUI::Menu>> g_app_category_menus;
+
+struct ThemeMetadata {
+    String name;
+    String path;
+};
+
+Color g_menu_selection_color;
+
+int g_theme_index { 0 };
+Vector<ThemeMetadata> g_themes;
+RefPtr<GUI::Menu> g_themes_menu;
+
+static NonnullRefPtr<GUI::Menu> build_system_menu();
+
+int main(int argc, char** argv)
+{
+    GUI::Application app(argc, argv);
+
+    auto menu = build_system_menu();
+
+    auto menubar = make<GUI::MenuBar>();
+    menubar->add_menu(move(menu));
+
+    app.set_menubar(move(menubar));
+
+    // FIXME: This window is just so we can see that the menu works.
+    //        Once we have a way to make this the default system menu we can drop this.
+    auto window = GUI::Window::construct();
+    window->show();
+
+    return app.exec();
+}
+
+NonnullRefPtr<GUI::Menu> build_system_menu()
+{
+    HashTable<String> seen_app_categories;
+    {
+        Core::DirIterator dt("/res/apps", Core::DirIterator::SkipDots);
+        while (dt.has_next()) {
+            auto af_name = dt.next_path();
+            auto af_path = String::format("/res/apps/%s", af_name.characters());
+            auto af = Core::ConfigFile::open(af_path);
+            if (!af->has_key("App", "Name") || !af->has_key("App", "Executable"))
+                continue;
+            auto app_name = af->read_entry("App", "Name");
+            auto app_executable = af->read_entry("App", "Executable");
+            auto app_category = af->read_entry("App", "Category");
+            auto app_icon_path = af->read_entry("Icons", "16x16");
+            g_apps.append({ app_executable, app_name, app_icon_path, app_category });
+            seen_app_categories.set(app_category);
+        }
+    }
+
+    Vector<String> sorted_app_categories;
+    for (auto& category : seen_app_categories)
+        sorted_app_categories.append(category);
+    quick_sort(sorted_app_categories.begin(), sorted_app_categories.end(), [](auto& a, auto& b) { return a < b; });
+
+    u8 system_menu_name[] = { 0xc3, 0xb8, 0 };
+    auto system_menu = GUI::Menu::construct(String((const char*)system_menu_name));
+
+    // First we construct all the necessary app category submenus.
+    for (const auto& category : sorted_app_categories) {
+
+        if (g_app_category_menus.contains(category))
+            continue;
+        auto category_menu = GUI::Menu::construct(category);
+        system_menu->add_submenu(category_menu);
+        g_app_category_menus.set(category, move(category_menu));
+    }
+
+    // Then we create and insert all the app menu items into the right place.
+    int app_identifier = 0;
+    for (const auto& app : g_apps) {
+        RefPtr<Gfx::Bitmap> icon;
+        if (!app.icon_path.is_empty())
+            icon = Gfx::Bitmap::load_from_file(app.icon_path);
+
+        if (icon)
+            dbg() << "App " << app.name << " has icon with size " << icon->size();
+
+        auto parent_menu = g_app_category_menus.get(app.category).value_or(*system_menu);
+        parent_menu->add_action(GUI::Action::create(app.name, icon.ptr(), [app_identifier](auto&) {
+            dbg() << "Activated app with ID " << app_identifier;
+            if (fork() == 0) {
+                const auto& bin = g_apps[app_identifier].executable;
+                execl(bin.characters(), bin.characters(), nullptr);
+                ASSERT_NOT_REACHED();
+            }
+        }));
+        ++app_identifier;
+    }
+
+    system_menu->add_separator();
+
+    g_themes_menu = GUI::Menu::construct("Themes");
+
+    system_menu->add_submenu(*g_themes_menu);
+
+    {
+        Core::DirIterator dt("/res/themes", Core::DirIterator::SkipDots);
+        while (dt.has_next()) {
+            auto theme_name = dt.next_path();
+            auto theme_path = String::format("/res/themes/%s", theme_name.characters());
+            g_themes.append({ FileSystemPath(theme_name).title(), theme_path });
+        }
+        quick_sort(g_themes.begin(), g_themes.end(), [](auto& a, auto& b) { return a.name < b.name; });
+    }
+
+    {
+        int theme_identifier = 0;
+        for (auto& theme : g_themes) {
+            g_themes_menu->add_action(GUI::Action::create(theme.name, [theme_identifier](auto&) {
+                auto& theme = g_themes[theme_identifier];
+                dbg() << "Theme switched to " << theme.name << " at path " << theme.path;
+                // FIXME: Tell WindowServer to switch theme!
+            }));
+            ++theme_identifier;
+        }
+    }
+
+    system_menu->add_separator();
+    system_menu->add_action(GUI::Action::create("About...", Gfx::Bitmap::load_from_file("/res/icons/16x16/ladybug.png"), [](auto&) {
+        if (fork() == 0) {
+            execl("/bin/About", "/bin/About", nullptr);
+            ASSERT_NOT_REACHED();
+        }
+    }));
+    system_menu->add_separator();
+    system_menu->add_action(GUI::Action::create("Shutdown...", [](auto&) {
+        if (fork() == 0) {
+            execl("/bin/SystemDialog", "/bin/SystemDialog", "--shutdown", nullptr);
+            ASSERT_NOT_REACHED();
+        }
+    }));
+
+    return system_menu;
+}

Kernel/build-root-filesystem.sh

@@ -129,6 +129,7 @@ cp ../Applications/PaintBrush/PaintBrush mnt/bin/PaintBrush
 cp ../Applications/QuickShow/QuickShow mnt/bin/QuickShow
 cp ../Applications/Piano/Piano mnt/bin/Piano
 cp ../Applications/SystemDialog/SystemDialog mnt/bin/SystemDialog
+cp ../Applications/SystemMenu/SystemMenu mnt/bin/SystemMenu
 cp ../Applications/ChanViewer/ChanViewer mnt/bin/ChanViewer
 cp ../Applications/Calculator/Calculator mnt/bin/Calculator
 cp ../Applications/SoundPlayer/SoundPlayer mnt/bin/SoundPlayer