LibGUI+FileManager: Merge GDirectoryModel into GFileSystemModel

We used to have two different models for displaying file system contents:
the FileManager-grade table-like directory model, which exposed rich data
(such as file icons with integrated image previews) about contents of a
single directory, and the tree-like GFileSystemModel, which only exposed
a tree of file names with very basic info about them.

This commit unifies the two. The new GFileSystemModel can be used both as a
tree-like and as a table-like model, or in fact in both ways simultaneously.
It exposes rich data about a file system subtree rooted at the given root.

The users of the two previous models are all ported to use this new model.

7 files changed, 531 insertions, 642 deletions

diff --git a/Libraries/LibGUI/GDirectoryModel.cpp b/Libraries/LibGUI/GDirectoryModel.cpp
deleted file mode 100644
index e4a6cda880..0000000000
--- a/Libraries/LibGUI/GDirectoryModel.cpp
+++ /dev/null
@@ -1,373 +0,0 @@
-#include "GDirectoryModel.h"
-#include <AK/FileSystemPath.h>
-#include <AK/StringBuilder.h>
-#include <LibCore/CDirIterator.h>
-#include <LibDraw/GraphicsBitmap.h>
-#include <LibGUI/GPainter.h>
-#include <LibThread/BackgroundAction.h>
-#include <dirent.h>
-#include <grp.h>
-#include <pwd.h>
-#include <stdio.h>
-#include <unistd.h>
-
-static HashMap<String, RefPtr<GraphicsBitmap>> s_thumbnail_cache;
-
-static RefPtr<GraphicsBitmap> render_thumbnail(const StringView& path)
-{
-    auto png_bitmap = GraphicsBitmap::load_from_file(path);
-    if (!png_bitmap)
-        return nullptr;
-    auto thumbnail = GraphicsBitmap::create(png_bitmap->format(), { 32, 32 });
-    Painter painter(*thumbnail);
-    painter.draw_scaled_bitmap(thumbnail->rect(), *png_bitmap, png_bitmap->rect());
-    return thumbnail;
-}
-
-GDirectoryModel::GDirectoryModel()
-{
-    m_directory_icon = GIcon::default_icon("filetype-folder");
-    m_file_icon = GIcon::default_icon("filetype-unknown");
-    m_symlink_icon = GIcon::default_icon("filetype-symlink");
-    m_socket_icon = GIcon::default_icon("filetype-socket");
-    m_executable_icon = GIcon::default_icon("filetype-executable");
-    m_filetype_image_icon = GIcon::default_icon("filetype-image");
-    m_filetype_sound_icon = GIcon::default_icon("filetype-sound");
-    m_filetype_html_icon = GIcon::default_icon("filetype-html");
-
-    setpwent();
-    while (auto* passwd = getpwent())
-        m_user_names.set(passwd->pw_uid, passwd->pw_name);
-    endpwent();
-
-    setgrent();
-    while (auto* group = getgrent())
-        m_group_names.set(group->gr_gid, group->gr_name);
-    endgrent();
-}
-
-GDirectoryModel::~GDirectoryModel()
-{
-}
-
-int GDirectoryModel::row_count(const GModelIndex&) const
-{
-    return m_directories.size() + m_files.size();
-}
-
-int GDirectoryModel::column_count(const GModelIndex&) const
-{
-    return Column::__Count;
-}
-
-String GDirectoryModel::column_name(int column) const
-{
-    switch (column) {
-    case Column::Icon:
-        return "";
-    case Column::Name:
-        return "Name";
-    case Column::Size:
-        return "Size";
-    case Column::Owner:
-        return "Owner";
-    case Column::Group:
-        return "Group";
-    case Column::Permissions:
-        return "Mode";
-    case Column::ModificationTime:
-        return "Modified";
-    case Column::Inode:
-        return "Inode";
-    }
-    ASSERT_NOT_REACHED();
-}
-
-GModel::ColumnMetadata GDirectoryModel::column_metadata(int column) const
-{
-    switch (column) {
-    case Column::Icon:
-        return { 16, TextAlignment::Center, nullptr, GModel::ColumnMetadata::Sortable::False };
-    case Column::Name:
-        return { 120, TextAlignment::CenterLeft };
-    case Column::Size:
-        return { 80, TextAlignment::CenterRight };
-    case Column::Owner:
-        return { 50, TextAlignment::CenterLeft };
-    case Column::Group:
-        return { 50, TextAlignment::CenterLeft };
-    case Column::ModificationTime:
-        return { 110, TextAlignment::CenterLeft };
-    case Column::Permissions:
-        return { 65, TextAlignment::CenterLeft };
-    case Column::Inode:
-        return { 60, TextAlignment::CenterRight };
-    }
-    ASSERT_NOT_REACHED();
-}
-
-bool GDirectoryModel::fetch_thumbnail_for(const Entry& entry)
-{
-    // See if we already have the thumbnail
-    // we're looking for in the cache.
-    auto path = entry.full_path(*this);
-    auto it = s_thumbnail_cache.find(path);
-    if (it != s_thumbnail_cache.end()) {
-        if (!(*it).value)
-            return false;
-        entry.thumbnail = (*it).value;
-        return true;
-    }
-
-    // Otherwise, arrange to render the thumbnail
-    // in background and make it available later.
-
-    s_thumbnail_cache.set(path, nullptr);
-    m_thumbnail_progress_total++;
-
-    auto directory_model = make_weak_ptr();
-
-    LibThread::BackgroundAction<RefPtr<GraphicsBitmap>>::create(
-        [path] {
-            return render_thumbnail(path);
-        },
-
-        [this, path, directory_model](auto thumbnail) {
-            s_thumbnail_cache.set(path, move(thumbnail));
-
-            // class was destroyed, no need to update progress or call any event handlers.
-            if (directory_model.is_null())
-                return;
-
-            m_thumbnail_progress++;
-            if (on_thumbnail_progress)
-                on_thumbnail_progress(m_thumbnail_progress, m_thumbnail_progress_total);
-            if (m_thumbnail_progress == m_thumbnail_progress_total) {
-                m_thumbnail_progress = 0;
-                m_thumbnail_progress_total = 0;
-            }
-
-            did_update();
-        });
-
-    return false;
-}
-
-GIcon GDirectoryModel::icon_for_file(const mode_t mode, const String name) const
-{
-    if (S_ISDIR(mode))
-        return m_directory_icon;
-    if (S_ISLNK(mode))
-        return m_symlink_icon;
-    if (S_ISSOCK(mode))
-        return m_socket_icon;
-    if (mode & S_IXUSR)
-        return m_executable_icon;
-    if (name.to_lowercase().ends_with(".wav"))
-        return m_filetype_sound_icon;
-    if (name.to_lowercase().ends_with(".html"))
-        return m_filetype_html_icon;
-    if (name.to_lowercase().ends_with(".png")) {
-        return m_filetype_image_icon;
-    }
-    return m_file_icon;
-}
-
-GIcon GDirectoryModel::icon_for(const Entry& entry) const
-{
-    if (entry.name.to_lowercase().ends_with(".png")) {
-        if (!entry.thumbnail) {
-            if (!const_cast<GDirectoryModel*>(this)->fetch_thumbnail_for(entry))
-                return m_filetype_image_icon;
-        }
-        return GIcon(m_filetype_image_icon.bitmap_for_size(16), *entry.thumbnail);
-    }
-
-    return icon_for_file(entry.mode, entry.name);
-}
-
-static String permission_string(mode_t mode)
-{
-    StringBuilder builder;
-    if (S_ISDIR(mode))
-        builder.append("d");
-    else if (S_ISLNK(mode))
-        builder.append("l");
-    else if (S_ISBLK(mode))
-        builder.append("b");
-    else if (S_ISCHR(mode))
-        builder.append("c");
-    else if (S_ISFIFO(mode))
-        builder.append("f");
-    else if (S_ISSOCK(mode))
-        builder.append("s");
-    else if (S_ISREG(mode))
-        builder.append("-");
-    else
-        builder.append("?");
-
-    builder.appendf("%c%c%c%c%c%c%c%c",
-        mode & S_IRUSR ? 'r' : '-',
-        mode & S_IWUSR ? 'w' : '-',
-        mode & S_ISUID ? 's' : (mode & S_IXUSR ? 'x' : '-'),
-        mode & S_IRGRP ? 'r' : '-',
-        mode & S_IWGRP ? 'w' : '-',
-        mode & S_ISGID ? 's' : (mode & S_IXGRP ? 'x' : '-'),
-        mode & S_IROTH ? 'r' : '-',
-        mode & S_IWOTH ? 'w' : '-');
-
-    if (mode & S_ISVTX)
-        builder.append("t");
-    else
-        builder.appendf("%c", mode & S_IXOTH ? 'x' : '-');
-    return builder.to_string();
-}
-
-String GDirectoryModel::name_for_uid(uid_t uid) const
-{
-    auto it = m_user_names.find(uid);
-    if (it == m_user_names.end())
-        return String::number(uid);
-    return (*it).value;
-}
-
-String GDirectoryModel::name_for_gid(uid_t gid) const
-{
-    auto it = m_user_names.find(gid);
-    if (it == m_user_names.end())
-        return String::number(gid);
-    return (*it).value;
-}
-
-GVariant GDirectoryModel::data(const GModelIndex& index, Role role) const
-{
-    ASSERT(is_valid(index));
-    auto& entry = this->entry(index.row());
-    if (role == Role::Custom) {
-        ASSERT(index.column() == Column::Name);
-        return entry.full_path(*this);
-    }
-    if (role == Role::DragData) {
-        if (index.column() == Column::Name) {
-            StringBuilder builder;
-            builder.append("file://");
-            builder.append(entry.full_path(*this));
-            return builder.to_string();
-        }
-        return {};
-    }
-    if (role == Role::Sort) {
-        switch (index.column()) {
-        case Column::Icon:
-            return entry.is_directory() ? 0 : 1;
-        case Column::Name:
-            return entry.name;
-        case Column::Size:
-            return (int)entry.size;
-        case Column::Owner:
-            return name_for_uid(entry.uid);
-        case Column::Group:
-            return name_for_gid(entry.gid);
-        case Column::Permissions:
-            return permission_string(entry.mode);
-        case Column::ModificationTime:
-            return entry.mtime;
-        case Column::Inode:
-            return (int)entry.inode;
-        }
-        ASSERT_NOT_REACHED();
-    }
-    if (role == Role::Display) {
-        switch (index.column()) {
-        case Column::Icon:
-            return icon_for(entry);
-        case Column::Name:
-            return entry.name;
-        case Column::Size:
-            return (int)entry.size;
-        case Column::Owner:
-            return name_for_uid(entry.uid);
-        case Column::Group:
-            return name_for_gid(entry.gid);
-        case Column::Permissions:
-            return permission_string(entry.mode);
-        case Column::ModificationTime:
-            return timestamp_string(entry.mtime);
-        case Column::Inode:
-            return (int)entry.inode;
-        }
-    }
-    if (role == Role::Icon) {
-        return icon_for(entry);
-    }
-    return {};
-}
-
-void GDirectoryModel::update()
-{
-    CDirIterator di(m_path, CDirIterator::SkipDots);
-    if (di.has_error()) {
-        fprintf(stderr, "CDirIterator: %s\n", di.error_string());
-        exit(1);
-    }
-
-    m_directories.clear();
-    m_files.clear();
-
-    m_bytes_in_files = 0;
-    while (di.has_next()) {
-        String name = di.next_path();
-        Entry entry;
-        entry.name = name;
-
-        struct stat st;
-        int rc = lstat(String::format("%s/%s", m_path.characters(), name.characters()).characters(), &st);
-        if (rc < 0) {
-            perror("lstat");
-            continue;
-        }
-        entry.size = st.st_size;
-        entry.mode = st.st_mode;
-        entry.uid = st.st_uid;
-        entry.gid = st.st_gid;
-        entry.inode = st.st_ino;
-        entry.mtime = st.st_mtime;
-        auto& entries = S_ISDIR(st.st_mode) ? m_directories : m_files;
-        entries.append(move(entry));
-
-        m_bytes_in_files += st.st_size;
-    }
-
-    did_update();
-}
-
-void GDirectoryModel::open(const StringView& a_path)
-{
-    auto path = canonicalized_path(a_path);
-    if (m_path == path)
-        return;
-    DIR* dirp = opendir(path.characters());
-    if (!dirp)
-        return;
-    closedir(dirp);
-    if (m_notifier) {
-        close(m_notifier->fd());
-        m_notifier = nullptr;
-    }
-    m_path = path;
-    int watch_fd = watch_file(path.characters(), path.length());
-    if (watch_fd < 0) {
-        perror("watch_file");
-    } else {
-        m_notifier = CNotifier::construct(watch_fd, CNotifier::Event::Read);
-        m_notifier->on_ready_to_read = [this] {
-            update();
-            char buffer[32];
-            int rc = read(m_notifier->fd(), buffer, sizeof(buffer));
-            ASSERT(rc >= 0);
-        };
-    }
-    if (on_path_change)
-        on_path_change();
-    update();
-}
diff --git a/Libraries/LibGUI/GDirectoryModel.h b/Libraries/LibGUI/GDirectoryModel.h
deleted file mode 100644
index 01930838b8..0000000000
--- a/Libraries/LibGUI/GDirectoryModel.h
+++ /dev/null
@@ -1,106 +0,0 @@
-#pragma once
-
-#include <AK/HashMap.h>
-#include <LibCore/CNotifier.h>
-#include <LibGUI/GModel.h>
-#include <sys/stat.h>
-#include <time.h>
-
-class GDirectoryModel final : public GModel
-    , public Weakable<GDirectoryModel> {
-public:
-    static NonnullRefPtr<GDirectoryModel> create() { return adopt(*new GDirectoryModel); }
-    virtual ~GDirectoryModel() override;
-
-    enum Column {
-        Icon = 0,
-        Name,
-        Size,
-        Owner,
-        Group,
-        Permissions,
-        ModificationTime,
-        Inode,
-        __Count,
-    };
-
-    virtual int row_count(const GModelIndex& = GModelIndex()) const override;
-    virtual int column_count(const GModelIndex& = GModelIndex()) const override;
-    virtual String column_name(int column) const override;
-    virtual ColumnMetadata column_metadata(int column) const override;
-    virtual GVariant data(const GModelIndex&, Role = Role::Display) const override;
-    virtual void update() override;
-
-    String path() const { return m_path; }
-    void open(const StringView& path);
-    size_t bytes_in_files() const { return m_bytes_in_files; }
-
-    Function<void(int done, int total)> on_thumbnail_progress;
-    Function<void()> on_path_change;
-
-    struct Entry {
-        String name;
-        size_t size { 0 };
-        mode_t mode { 0 };
-        uid_t uid { 0 };
-        uid_t gid { 0 };
-        ino_t inode { 0 };
-        time_t mtime { 0 };
-        mutable RefPtr<GraphicsBitmap> thumbnail;
-        bool is_directory() const { return S_ISDIR(mode); }
-        bool is_executable() const { return mode & S_IXUSR; }
-        String full_path(const GDirectoryModel& model) const { return String::format("%s/%s", model.path().characters(), name.characters()); }
-    };
-
-    const Entry& entry(int index) const
-    {
-        if (index < m_directories.size())
-            return m_directories[index];
-        return m_files[index - m_directories.size()];
-    }
-
-    GIcon icon_for_file(const mode_t mode, const String name) const;
-
-    static String timestamp_string(time_t timestamp)
-    {
-        auto* tm = localtime(&timestamp);
-        return String::format("%4u-%02u-%02u %02u:%02u:%02u",
-            tm->tm_year + 1900,
-            tm->tm_mon + 1,
-            tm->tm_mday,
-            tm->tm_hour,
-            tm->tm_min,
-            tm->tm_sec);
-    }
-
-private:
-    GDirectoryModel();
-
-    String name_for_uid(uid_t) const;
-    String name_for_gid(gid_t) const;
-
-    bool fetch_thumbnail_for(const Entry& entry);
-    GIcon icon_for(const Entry& entry) const;
-
-    String m_path;
-    Vector<Entry> m_files;
-    Vector<Entry> m_directories;
-    size_t m_bytes_in_files;
-
-    GIcon m_directory_icon;
-    GIcon m_file_icon;
-    GIcon m_symlink_icon;
-    GIcon m_socket_icon;
-    GIcon m_executable_icon;
-    GIcon m_filetype_image_icon;
-    GIcon m_filetype_sound_icon;
-    GIcon m_filetype_html_icon;
-
-    HashMap<uid_t, String> m_user_names;
-    HashMap<gid_t, String> m_group_names;
-
-    RefPtr<CNotifier> m_notifier;
-
-    unsigned m_thumbnail_progress { 0 };
-    unsigned m_thumbnail_progress_total { 0 };
-};
diff --git a/Libraries/LibGUI/GFilePicker.cpp b/Libraries/LibGUI/GFilePicker.cpp
index 48d03d96c3..41e348436d 100644
--- a/Libraries/LibGUI/GFilePicker.cpp
+++ b/Libraries/LibGUI/GFilePicker.cpp
@@ -4,8 +4,8 @@
 #include <LibGUI/GAction.h>
 #include <LibGUI/GBoxLayout.h>
 #include <LibGUI/GButton.h>
-#include <LibGUI/GDirectoryModel.h>
 #include <LibGUI/GFilePicker.h>
+#include <LibGUI/GFileSystemModel.h>
 #include <LibGUI/GInputBox.h>
 #include <LibGUI/GLabel.h>
 #include <LibGUI/GMessageBox.h>
@@ -48,7 +48,7 @@ Optional<String> GFilePicker::get_save_filepath(const String& title, const Strin
 
 GFilePicker::GFilePicker(Mode mode, const StringView& file_name, const StringView& path, CObject* parent)
     : GDialog(parent)
-    , m_model(GDirectoryModel::create())
+    , m_model(GFileSystemModel::create())
     , m_mode(mode)
 {
     set_title(m_mode == Mode::Open ? "Open File" : "Save File");
@@ -80,25 +80,25 @@ GFilePicker::GFilePicker(Mode mode, const StringView& file_name, const StringVie
 
     m_view = GTableView::construct(vertical_container);
     m_view->set_model(GSortingProxyModel::create(*m_model));
-    m_view->set_column_hidden(GDirectoryModel::Column::Owner, true);
-    m_view->set_column_hidden(GDirectoryModel::Column::Group, true);
-    m_view->set_column_hidden(GDirectoryModel::Column::Permissions, true);
-    m_view->set_column_hidden(GDirectoryModel::Column::Inode, true);
-    m_model->open(path);
+    m_view->set_column_hidden(GFileSystemModel::Column::Owner, true);
+    m_view->set_column_hidden(GFileSystemModel::Column::Group, true);
+    m_view->set_column_hidden(GFileSystemModel::Column::Permissions, true);
+    m_view->set_column_hidden(GFileSystemModel::Column::Inode, true);
+    m_model->set_root_path(path);
 
     location_textbox->on_return_pressed = [&] {
-        m_model->open(location_textbox->text());
+        m_model->set_root_path(location_textbox->text());
         clear_preview();
     };
 
     auto open_parent_directory_action = GAction::create("Open parent directory", { Mod_Alt, Key_Up }, GraphicsBitmap::load_from_file("/res/icons/16x16/open-parent-directory.png"), [this](const GAction&) {
-        m_model->open(String::format("%s/..", m_model->path().characters()));
+        m_model->set_root_path(String::format("%s/..", m_model->root_path().characters()));
         clear_preview();
     });
     toolbar->add_action(*open_parent_directory_action);
 
     auto go_home_action = GCommonActions::make_go_home_action([this](auto&) {
-        m_model->open(get_current_user_home_path());
+        m_model->set_root_path(get_current_user_home_path());
     });
     toolbar->add_action(go_home_action);
     toolbar->add_separator();
@@ -107,7 +107,7 @@ GFilePicker::GFilePicker(Mode mode, const StringView& file_name, const StringVie
         auto input_box = GInputBox::construct("Enter name:", "New directory", this);
         if (input_box->exec() == GInputBox::ExecOK && !input_box->text_value().is_empty()) {
             auto new_dir_path = FileSystemPath(String::format("%s/%s",
-                                                   m_model->path().characters(),
+                                                   m_model->root_path().characters(),
                                                    input_box->text_value().characters()))
                                     .string();
             int rc = mkdir(new_dir_path.characters(), 0777);
@@ -147,13 +147,13 @@ GFilePicker::GFilePicker(Mode mode, const StringView& file_name, const StringVie
     m_view->on_selection = [this](auto& index) {
         auto& filter_model = (GSortingProxyModel&)*m_view->model();
         auto local_index = filter_model.map_to_target(index);
-        const GDirectoryModel::Entry& entry = m_model->entry(local_index.row());
-        FileSystemPath path(String::format("%s/%s", m_model->path().characters(), entry.name.characters()));
+        const GFileSystemModel::Node& node = m_model->node(local_index);
+        FileSystemPath path { node.full_path(m_model) };
 
         clear_preview();
 
-        if (!entry.is_directory())
-            m_filename_textbox->set_text(entry.name);
+        if (!node.is_directory())
+            m_filename_textbox->set_text(node.name);
         set_preview(path);
     };
 
@@ -183,12 +183,12 @@ GFilePicker::GFilePicker(Mode mode, const StringView& file_name, const StringVie
     m_view->on_activation = [this](auto& index) {
         auto& filter_model = (GSortingProxyModel&)*m_view->model();
         auto local_index = filter_model.map_to_target(index);
-        const GDirectoryModel::Entry& entry = m_model->entry(local_index.row());
-        FileSystemPath path(String::format("%s/%s", m_model->path().characters(), entry.name.characters()));
+        const GFileSystemModel::Node& node = m_model->node(local_index);
+        auto path = node.full_path(m_model);
 
-        if (entry.is_directory()) {
-            m_model->open(path.string());
-            // NOTE: 'entry' is invalid from here on
+        if (node.is_directory()) {
+            m_model->set_root_path(path);
+            // NOTE: 'node' is invalid from here on
         } else {
             on_file_return();
         }
@@ -247,7 +247,7 @@ void GFilePicker::clear_preview()
 
 void GFilePicker::on_file_return()
 {
-    FileSystemPath path(String::format("%s/%s", m_model->path().characters(), m_filename_textbox->text().characters()));
+    FileSystemPath path(String::format("%s/%s", m_model->root_path().characters(), m_filename_textbox->text().characters()));
 
     if (GFilePicker::file_exists(path.string()) && m_mode == Mode::Save) {
         auto result = GMessageBox::show("File already exists, overwrite?", "Existing File", GMessageBox::Type::Warning, GMessageBox::InputType::OKCancel);
diff --git a/Libraries/LibGUI/GFilePicker.h b/Libraries/LibGUI/GFilePicker.h
index d4f2c35aa5..169f59fd8e 100644
--- a/Libraries/LibGUI/GFilePicker.h
+++ b/Libraries/LibGUI/GFilePicker.h
@@ -4,7 +4,7 @@
 #include <LibGUI/GDialog.h>
 #include <LibGUI/GTableView.h>
 
-class GDirectoryModel;
+class GFileSystemModel;
 class GLabel;
 class GTextBox;
 
@@ -44,7 +44,7 @@ private:
     }
 
     RefPtr<GTableView> m_view;
-    NonnullRefPtr<GDirectoryModel> m_model;
+    NonnullRefPtr<GFileSystemModel> m_model;
     FileSystemPath m_selected_file;
 
     RefPtr<GTextBox> m_filename_textbox;
diff --git a/Libraries/LibGUI/GFileSystemModel.cpp b/Libraries/LibGUI/GFileSystemModel.cpp
index 637fac93ef..198ca8b098 100644
--- a/Libraries/LibGUI/GFileSystemModel.cpp
+++ b/Libraries/LibGUI/GFileSystemModel.cpp
@@ -1,126 +1,141 @@
 #include <AK/FileSystemPath.h>
 #include <AK/StringBuilder.h>
 #include <LibCore/CDirIterator.h>
+#include <LibDraw/GraphicsBitmap.h>
 #include <LibGUI/GFileSystemModel.h>
+#include <LibGUI/GPainter.h>
+#include <LibThread/BackgroundAction.h>
 #include <dirent.h>
+#include <grp.h>
+#include <pwd.h>
 #include <stdio.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
-struct GFileSystemModel::Node {
-    String name;
-    Node* parent { nullptr };
-    Vector<Node*> children;
-    enum Type {
-        Unknown,
-        Directory,
-        File
-    };
-    Type type { Unknown };
-
-    bool has_traversed { false };
-
-    GModelIndex index(const GFileSystemModel& model) const
-    {
-        if (!parent)
-            return model.create_index(0, 0, const_cast<Node*>(this));
-        for (int row = 0; row < parent->children.size(); ++row) {
-            if (parent->children[row] == this)
-                return model.create_index(row, 0, const_cast<Node*>(this));
-        }
-        ASSERT_NOT_REACHED();
+GModelIndex GFileSystemModel::Node::index(const GFileSystemModel& model, int column) const
+{
+    if (!parent)
+        return {};
+    for (int row = 0; row < parent->children.size(); ++row) {
+        if (&parent->children[row] == this)
+            return model.create_index(row, column, const_cast<Node*>(this));
     }
+    ASSERT_NOT_REACHED();
+}
 
-    void cleanup()
-    {
-        for (auto& child: children) {
-            child->cleanup();
-            delete child;
-        }
-        children.clear();
+bool GFileSystemModel::Node::fetch_data_using_lstat(const String& full_path)
+{
+    struct stat st;
+    int rc = lstat(full_path.characters(), &st);
+    if (rc < 0) {
+        perror("lstat");
+        return false;
     }
 
-    void traverse_if_needed(const GFileSystemModel& model)
-    {
-        if (type != Node::Directory || has_traversed)
-            return;
-        has_traversed = true;
+    size = st.st_size;
+    mode = st.st_mode;
+    uid = st.st_uid;
+    gid = st.st_gid;
+    inode = st.st_ino;
+    mtime = st.st_mtime;
 
-        auto full_path = this->full_path(model);
-        CDirIterator di(full_path, CDirIterator::SkipDots);
-        if (di.has_error()) {
-            fprintf(stderr, "CDirIterator: %s\n", di.error_string());
-            return;
-        }
+    return true;
+}
 
-        while (di.has_next()) {
-            String name = di.next_path();
-            struct stat st;
-            int rc = lstat(String::format("%s/%s", full_path.characters(), name.characters()).characters(), &st);
-            if (rc < 0) {
-                perror("lstat");
-                continue;
-            }
-            if (model.m_mode == DirectoriesOnly && !S_ISDIR(st.st_mode))
-                continue;
-            auto* child = new Node;
-            child->name = name;
-            child->type = S_ISDIR(st.st_mode) ? Node::Type::Directory : Node::Type::File;
-            child->parent = this;
-            children.append(child);
-        }
+void GFileSystemModel::Node::traverse_if_needed(const GFileSystemModel& model)
+{
+    if (!is_directory() || has_traversed)
+        return;
+    has_traversed = true;
+    total_size = 0;
+
+    auto full_path = this->full_path(model);
+    CDirIterator di(full_path, CDirIterator::SkipDots);
+    if (di.has_error()) {
+        fprintf(stderr, "CDirIterator: %s\n", di.error_string());
+        return;
     }
 
-    void reify_if_needed(const GFileSystemModel& model)
-    {
-        traverse_if_needed(model);
-        if (type != Node::Type::Unknown)
-            return;
-        struct stat st;
-        auto full_path = this->full_path(model);
-        int rc = lstat(full_path.characters(), &st);
-        dbgprintf("lstat(%s) = %d\n", full_path.characters(), rc);
-        if (rc < 0) {
-            perror("lstat");
-            return;
-        }
-        type = S_ISDIR(st.st_mode) ? Node::Type::Directory : Node::Type::File;
+    while (di.has_next()) {
+        String name = di.next_path();
+        String child_path = String::format("%s/%s", full_path.characters(), name.characters());
+        NonnullOwnPtr<Node> child = make<Node>();
+        bool ok = child->fetch_data_using_lstat(child_path);
+        if (!ok)
+            continue;
+        if (model.m_mode == DirectoriesOnly && !S_ISDIR(child->mode))
+            continue;
+        child->name = name;
+        child->parent = this;
+        total_size += child->size;
+        children.append(move(child));
     }
 
-    String full_path(const GFileSystemModel& model) const
-    {
-        Vector<String, 32> lineage;
-        for (auto* ancestor = parent; ancestor; ancestor = ancestor->parent) {
-            lineage.append(ancestor->name);
-        }
-        StringBuilder builder;
-        builder.append(model.root_path());
-        for (int i = lineage.size() - 1; i >= 0; --i) {
-            builder.append('/');
-            builder.append(lineage[i]);
-        }
+    if (m_watch_fd >= 0)
+        return;
+
+    m_watch_fd = watch_file(full_path.characters(), full_path.length());
+    if (m_watch_fd < 0) {
+        perror("watch_file");
+        return;
+    }
+    fcntl(m_watch_fd, F_SETFD, FD_CLOEXEC);
+    dbg() << "Watching " << full_path << " for changes, m_watch_fd = " << m_watch_fd;
+    m_notifier = CNotifier::construct(m_watch_fd, CNotifier::Event::Read);
+    m_notifier->on_ready_to_read = [this, &model] {
+        char buffer[32];
+        int rc = read(m_notifier->fd(), buffer, sizeof(buffer));
+        ASSERT(rc >= 0);
+
+        has_traversed = false;
+        mode = 0;
+        children.clear();
+        reify_if_needed(model);
+        const_cast<GFileSystemModel&>(model).did_update();
+    };
+}
+
+void GFileSystemModel::Node::reify_if_needed(const GFileSystemModel& model)
+{
+    traverse_if_needed(model);
+    if (mode != 0)
+        return;
+    fetch_data_using_lstat(full_path(model));
+}
+
+String GFileSystemModel::Node::full_path(const GFileSystemModel& model) const
+{
+    Vector<String, 32> lineage;
+    for (auto* ancestor = parent; ancestor; ancestor = ancestor->parent) {
+        lineage.append(ancestor->name);
+    }
+    StringBuilder builder;
+    builder.append(model.root_path());
+    for (int i = lineage.size() - 1; i >= 0; --i) {
         builder.append('/');
-        builder.append(name);
-        return canonicalized_path(builder.to_string());
+        builder.append(lineage[i]);
     }
-};
+    builder.append('/');
+    builder.append(name);
+    return canonicalized_path(builder.to_string());
+}
 
-GModelIndex GFileSystemModel::index(const StringView& path) const
+GModelIndex GFileSystemModel::index(const StringView& path, int column) const
 {
     FileSystemPath canonical_path(path);
     const Node* node = m_root;
     if (canonical_path.string() == "/")
-        return m_root->index(*this);
+        return m_root->index(*this, column);
     for (int i = 0; i < canonical_path.parts().size(); ++i) {
         auto& part = canonical_path.parts()[i];
         bool found = false;
         for (auto& child : node->children) {
-            if (child->name == part) {
-                child->reify_if_needed(*this);
-                node = child;
+            if (child.name == part) {
+                const_cast<Node&>(child).reify_if_needed(*this);
+                node = &child;
                 found = true;
                 if (i == canonical_path.parts().size() - 1)
-                    return node->index(*this);
+                    return child.index(*this, column);
                 break;
             }
         }
@@ -130,12 +145,10 @@ GModelIndex GFileSystemModel::index(const StringView& path) const
     return {};
 }
 
-String GFileSystemModel::path(const GModelIndex& index) const
+String GFileSystemModel::full_path(const GModelIndex& index) const
 {
-    if (!index.is_valid())
-        return {};
-    auto& node = *(Node*)index.internal_data();
-    node.reify_if_needed(*this);
+    auto& node = this->node(index);
+    const_cast<Node&>(node).reify_if_needed(*this);
     return node.full_path(*this);
 }
 
@@ -143,9 +156,25 @@ GFileSystemModel::GFileSystemModel(const StringView& root_path, Mode mode)
     : m_root_path(canonicalized_path(root_path))
     , m_mode(mode)
 {
-    m_open_folder_icon = GIcon::default_icon("filetype-folder-open");
-    m_closed_folder_icon = GIcon::default_icon("filetype-folder");
+    m_directory_icon = GIcon::default_icon("filetype-folder");
     m_file_icon = GIcon::default_icon("filetype-unknown");
+    m_symlink_icon = GIcon::default_icon("filetype-symlink");
+    m_socket_icon = GIcon::default_icon("filetype-socket");
+    m_executable_icon = GIcon::default_icon("filetype-executable");
+    m_filetype_image_icon = GIcon::default_icon("filetype-image");
+    m_filetype_sound_icon = GIcon::default_icon("filetype-sound");
+    m_filetype_html_icon = GIcon::default_icon("filetype-html");
+
+    setpwent();
+    while (auto* passwd = getpwent())
+        m_user_names.set(passwd->pw_uid, passwd->pw_name);
+    endpwent();
+
+    setgrent();
+    while (auto* group = getgrent())
+        m_group_names.set(group->gr_gid, group->gr_name);
+    endgrent();
+
     update();
 }
 
@@ -153,73 +182,324 @@ GFileSystemModel::~GFileSystemModel()
 {
 }
 
-void GFileSystemModel::update()
+String GFileSystemModel::name_for_uid(uid_t uid) const
 {
-    cleanup();
+    auto it = m_user_names.find(uid);
+    if (it == m_user_names.end())
+        return String::number(uid);
+    return (*it).value;
+}
 
-    m_root = new Node;
-    m_root->name = m_root_path;
-    m_root->reify_if_needed(*this);
+String GFileSystemModel::name_for_gid(uid_t gid) const
+{
+    auto it = m_user_names.find(gid);
+    if (it == m_user_names.end())
+        return String::number(gid);
+    return (*it).value;
+}
 
-    did_update();
+static String permission_string(mode_t mode)
+{
+    StringBuilder builder;
+    if (S_ISDIR(mode))
+        builder.append("d");
+    else if (S_ISLNK(mode))
+        builder.append("l");
+    else if (S_ISBLK(mode))
+        builder.append("b");
+    else if (S_ISCHR(mode))
+        builder.append("c");
+    else if (S_ISFIFO(mode))
+        builder.append("f");
+    else if (S_ISSOCK(mode))
+        builder.append("s");
+    else if (S_ISREG(mode))
+        builder.append("-");
+    else
+        builder.append("?");
+
+    builder.appendf("%c%c%c%c%c%c%c%c",
+        mode & S_IRUSR ? 'r' : '-',
+        mode & S_IWUSR ? 'w' : '-',
+        mode & S_ISUID ? 's' : (mode & S_IXUSR ? 'x' : '-'),
+        mode & S_IRGRP ? 'r' : '-',
+        mode & S_IWGRP ? 'w' : '-',
+        mode & S_ISGID ? 's' : (mode & S_IXGRP ? 'x' : '-'),
+        mode & S_IROTH ? 'r' : '-',
+        mode & S_IWOTH ? 'w' : '-');
+
+    if (mode & S_ISVTX)
+        builder.append("t");
+    else
+        builder.appendf("%c", mode & S_IXOTH ? 'x' : '-');
+    return builder.to_string();
 }
 
-void GFileSystemModel::cleanup()
+void GFileSystemModel::set_root_path(const StringView& root_path)
 {
-    if (m_root) {
-        m_root->cleanup();
-        delete m_root;
-        m_root = nullptr;
-    }
+    m_root_path = canonicalized_path(root_path);
+
+    if (on_root_path_change)
+        on_root_path_change();
+
+    update();
+}
+
+void GFileSystemModel::update()
+{
+    m_root = make<Node>();
+    m_root->reify_if_needed(*this);
+
+    did_update();
 }
 
 int GFileSystemModel::row_count(const GModelIndex& index) const
 {
-    if (!index.is_valid())
-        return 1;
-    auto& node = *(Node*)index.internal_data();
+    Node& node = const_cast<Node&>(this->node(index));
     node.reify_if_needed(*this);
-    if (node.type == Node::Type::Directory)
+    if (node.is_directory())
         return node.children.size();
     return 0;
 }
 
+const GFileSystemModel::Node& GFileSystemModel::node(const GModelIndex& index) const
+{
+    if (!index.is_valid())
+        return *m_root;
+    return *(Node*)index.internal_data();
+}
+
 GModelIndex GFileSystemModel::index(int row, int column, const GModelIndex& parent) const
 {
-    if (!parent.is_valid())
-        return create_index(row, column, m_root);
-    auto& node = *(Node*)parent.internal_data();
-    return create_index(row, column, node.children[row]);
+    auto& node = this->node(parent);
+    const_cast<Node&>(node).reify_if_needed(*this);
+    if (row >= node.children.size())
+        return {};
+    return create_index(row, column, &node.children[row]);
 }
 
 GModelIndex GFileSystemModel::parent_index(const GModelIndex& index) const
 {
     if (!index.is_valid())
         return {};
-    auto& node = *(const Node*)index.internal_data();
+    auto& node = this->node(index);
     if (!node.parent) {
         ASSERT(&node == m_root);
         return {};
     }
-    return node.parent->index(*this);
+    return node.parent->index(*this, index.column());
 }
 
 GVariant GFileSystemModel::data(const GModelIndex& index, Role role) const
 {
-    if (!index.is_valid())
+    ASSERT(index.is_valid());
+    auto& node = this->node(index);
+
+    if (role == Role::Custom) {
+        // For GFileSystemModel, custom role means the full path.
+        ASSERT(index.column() == Column::Name);
+        return node.full_path(*this);
+    }
+
+    if (role == Role::DragData) {
+        if (index.column() == Column::Name) {
+            StringBuilder builder;
+            builder.append("file://");
+            builder.append(node.full_path(*this));
+            return builder.to_string();
+        }
         return {};
-    auto& node = *(const Node*)index.internal_data();
-    if (role == GModel::Role::Display)
-        return node.name;
-    if (role == GModel::Role::Icon) {
-        if (node.type == Node::Directory)
-            return m_closed_folder_icon;
-        return m_file_icon;
+    }
+
+    if (role == Role::Sort) {
+        switch (index.column()) {
+        case Column::Icon:
+            return node.is_directory() ? 0 : 1;
+        case Column::Name:
+            return node.name;
+        case Column::Size:
+            return (int)node.size;
+        case Column::Owner:
+            return name_for_uid(node.uid);
+        case Column::Group:
+            return name_for_gid(node.gid);
+        case Column::Permissions:
+            return permission_string(node.mode);
+        case Column::ModificationTime:
+            return node.mtime;
+        case Column::Inode:
+            return (int)node.inode;
+        }
+        ASSERT_NOT_REACHED();
+    }
+
+    if (role == Role::Display) {
+        switch (index.column()) {
+        case Column::Icon:
+            return icon_for(node);
+        case Column::Name:
+            return node.name;
+        case Column::Size:
+            return (int)node.size;
+        case Column::Owner:
+            return name_for_uid(node.uid);
+        case Column::Group:
+            return name_for_gid(node.gid);
+        case Column::Permissions:
+            return permission_string(node.mode);
+        case Column::ModificationTime:
+            return timestamp_string(node.mtime);
+        case Column::Inode:
+            return (int)node.inode;
+        }
+    }
+
+    if (role == Role::Icon) {
+        return icon_for(node);
     }
     return {};
 }
 
+GIcon GFileSystemModel::icon_for_file(const mode_t mode, const String& name) const
+{
+    if (S_ISDIR(mode))
+        return m_directory_icon;
+    if (S_ISLNK(mode))
+        return m_symlink_icon;
+    if (S_ISSOCK(mode))
+        return m_socket_icon;
+    if (mode & S_IXUSR)
+        return m_executable_icon;
+    if (name.to_lowercase().ends_with(".wav"))
+        return m_filetype_sound_icon;
+    if (name.to_lowercase().ends_with(".html"))
+        return m_filetype_html_icon;
+    if (name.to_lowercase().ends_with(".png"))
+        return m_filetype_image_icon;
+    return m_file_icon;
+}
+
+GIcon GFileSystemModel::icon_for(const Node& node) const
+{
+    if (node.name.to_lowercase().ends_with(".png")) {
+        if (!node.thumbnail) {
+            if (!const_cast<GFileSystemModel*>(this)->fetch_thumbnail_for(node))
+                return m_filetype_image_icon;
+        }
+        return GIcon(m_filetype_image_icon.bitmap_for_size(16), *node.thumbnail);
+    }
+
+    return icon_for_file(node.mode, node.name);
+}
+
+static HashMap<String, RefPtr<GraphicsBitmap>> s_thumbnail_cache;
+
+static RefPtr<GraphicsBitmap> render_thumbnail(const StringView& path)
+{
+    auto png_bitmap = GraphicsBitmap::load_from_file(path);
+    if (!png_bitmap)
+        return nullptr;
+    auto thumbnail = GraphicsBitmap::create(png_bitmap->format(), { 32, 32 });
+    Painter painter(*thumbnail);
+    painter.draw_scaled_bitmap(thumbnail->rect(), *png_bitmap, png_bitmap->rect());
+    return thumbnail;
+}
+
+bool GFileSystemModel::fetch_thumbnail_for(const Node& node)
+{
+    // See if we already have the thumbnail
+    // we're looking for in the cache.
+    auto path = node.full_path(*this);
+    auto it = s_thumbnail_cache.find(path);
+    if (it != s_thumbnail_cache.end()) {
+        if (!(*it).value)
+            return false;
+        node.thumbnail = (*it).value;
+        return true;
+    }
+
+    // Otherwise, arrange to render the thumbnail
+    // in background and make it available later.
+
+    s_thumbnail_cache.set(path, nullptr);
+    m_thumbnail_progress_total++;
+
+    auto weak_this = make_weak_ptr();
+
+    LibThread::BackgroundAction<RefPtr<GraphicsBitmap>>::create(
+        [path] {
+            return render_thumbnail(path);
+        },
+
+        [this, path, weak_this](auto thumbnail) {
+            s_thumbnail_cache.set(path, move(thumbnail));
+
+            // The model was destroyed, no need to update
+            // progress or call any event handlers.
+            if (weak_this.is_null())
+                return;
+
+            m_thumbnail_progress++;
+            if (on_thumbnail_progress)
+                on_thumbnail_progress(m_thumbnail_progress, m_thumbnail_progress_total);
+            if (m_thumbnail_progress == m_thumbnail_progress_total) {
+                m_thumbnail_progress = 0;
+                m_thumbnail_progress_total = 0;
+            }
+
+            did_update();
+        });
+
+    return false;
+}
+
 int GFileSystemModel::column_count(const GModelIndex&) const
 {
-    return 1;
+    return Column::__Count;
+}
+
+String GFileSystemModel::column_name(int column) const
+{
+    switch (column) {
+    case Column::Icon:
+        return "";
+    case Column::Name:
+        return "Name";
+    case Column::Size:
+        return "Size";
+    case Column::Owner:
+        return "Owner";
+    case Column::Group:
+        return "Group";
+    case Column::Permissions:
+        return "Mode";
+    case Column::ModificationTime:
+        return "Modified";
+    case Column::Inode:
+        return "Inode";
+    }
+    ASSERT_NOT_REACHED();
+}
+
+GModel::ColumnMetadata GFileSystemModel::column_metadata(int column) const
+{
+    switch (column) {
+    case Column::Icon:
+        return { 16, TextAlignment::Center, nullptr, GModel::ColumnMetadata::Sortable::False };
+    case Column::Name:
+        return { 120, TextAlignment::CenterLeft };
+    case Column::Size:
+        return { 80, TextAlignment::CenterRight };
+    case Column::Owner:
+        return { 50, TextAlignment::CenterLeft };
+    case Column::Group:
+        return { 50, TextAlignment::CenterLeft };
+    case Column::ModificationTime:
+        return { 110, TextAlignment::CenterLeft };
+    case Column::Permissions:
+        return { 65, TextAlignment::CenterLeft };
+    case Column::Inode:
+        return { 60, TextAlignment::CenterRight };
+    }
+    ASSERT_NOT_REACHED();
 }
diff --git a/Libraries/LibGUI/GFileSystemModel.h b/Libraries/LibGUI/GFileSystemModel.h
index 8e4e481ec8..3919193017 100644
--- a/Libraries/LibGUI/GFileSystemModel.h
+++ b/Libraries/LibGUI/GFileSystemModel.h
@@ -1,9 +1,15 @@
 #pragma once
 
+#include <AK/HashMap.h>
+#include <AK/NonnullOwnPtrVector.h>
+#include <LibCore/CNotifier.h>
 #include <LibGUI/GModel.h>
+#include <sys/stat.h>
+#include <time.h>
 
-class GFileSystemModel : public GModel {
-    friend class Node;
+class GFileSystemModel : public GModel
+    , public Weakable<GFileSystemModel> {
+    friend struct Node;
 
 public:
     enum Mode {
@@ -12,6 +18,53 @@ public:
         FilesAndDirectories
     };
 
+    enum Column {
+        Icon = 0,
+        Name,
+        Size,
+        Owner,
+        Group,
+        Permissions,
+        ModificationTime,
+        Inode,
+        __Count,
+    };
+
+    struct Node {
+        ~Node() { close(m_watch_fd); }
+
+        String name;
+        size_t size { 0 };
+        mode_t mode { 0 };
+        uid_t uid { 0 };
+        gid_t gid { 0 };
+        ino_t inode { 0 };
+        time_t mtime { 0 };
+
+        size_t total_size { 0 };
+
+        mutable RefPtr<GraphicsBitmap> thumbnail;
+        bool is_directory() const { return S_ISDIR(mode); }
+        bool is_executable() const { return mode & S_IXUSR; }
+
+        String full_path(const GFileSystemModel&) const;
+
+    private:
+        friend class GFileSystemModel;
+
+        Node* parent { nullptr };
+        NonnullOwnPtrVector<Node> children;
+        bool has_traversed { false };
+
+        int m_watch_fd { -1 };
+        RefPtr<CNotifier> m_notifier;
+
+        GModelIndex index(const GFileSystemModel&, int column) const;
+        void traverse_if_needed(const GFileSystemModel&);
+        void reify_if_needed(const GFileSystemModel&);
+        bool fetch_data_using_lstat(const String& full_path);
+    };
+
     static NonnullRefPtr<GFileSystemModel> create(const StringView& root_path = "/", Mode mode = Mode::FilesAndDirectories)
     {
         return adopt(*new GFileSystemModel(root_path, mode));
@@ -19,27 +72,63 @@ public:
     virtual ~GFileSystemModel() override;
 
     String root_path() const { return m_root_path; }
-    String path(const GModelIndex&) const;
-    GModelIndex index(const StringView& path) const;
+    void set_root_path(const StringView&);
+    String full_path(const GModelIndex&) const;
+    GModelIndex index(const StringView& path, int column) const;
+
+    const Node& node(const GModelIndex& index) const;
+    GIcon icon_for_file(const mode_t mode, const String& name) const;
+
+    Function<void(int done, int total)> on_thumbnail_progress;
+    Function<void()> on_root_path_change;
 
+    virtual int tree_column() const { return Column::Name; }
     virtual int row_count(const GModelIndex& = GModelIndex()) const override;
     virtual int column_count(const GModelIndex& = GModelIndex()) const override;
+    virtual String column_name(int column) const override;
+    virtual ColumnMetadata column_metadata(int column) const override;
     virtual GVariant data(const GModelIndex&, Role = Role::Display) const override;
     virtual void update() override;
     virtual GModelIndex parent_index(const GModelIndex&) const override;
     virtual GModelIndex index(int row, int column = 0, const GModelIndex& parent = GModelIndex()) const override;
 
+    static String timestamp_string(time_t timestamp)
+    {
+        auto* tm = localtime(&timestamp);
+        return String::format("%4u-%02u-%02u %02u:%02u:%02u",
+            tm->tm_year + 1900,
+            tm->tm_mon + 1,
+            tm->tm_mday,
+            tm->tm_hour,
+            tm->tm_min,
+            tm->tm_sec);
+    }
+
 private:
     GFileSystemModel(const StringView& root_path, Mode);
 
+    String name_for_uid(uid_t) const;
+    String name_for_gid(gid_t) const;
+
+    HashMap<uid_t, String> m_user_names;
+    HashMap<gid_t, String> m_group_names;
+
+    bool fetch_thumbnail_for(const Node& node);
+    GIcon icon_for(const Node& node) const;
+
     String m_root_path;
     Mode m_mode { Invalid };
+    OwnPtr<Node> m_root { nullptr };
 
-    struct Node;
-    Node* m_root { nullptr };
-    void cleanup();
-
-    GIcon m_open_folder_icon;
-    GIcon m_closed_folder_icon;
+    GIcon m_directory_icon;
     GIcon m_file_icon;
+    GIcon m_symlink_icon;
+    GIcon m_socket_icon;
+    GIcon m_executable_icon;
+    GIcon m_filetype_image_icon;
+    GIcon m_filetype_sound_icon;
+    GIcon m_filetype_html_icon;
+
+    unsigned m_thumbnail_progress { 0 };
+    unsigned m_thumbnail_progress_total { 0 };
 };
diff --git a/Libraries/LibGUI/Makefile b/Libraries/LibGUI/Makefile
index 7d71bf950a..51ab2ed7fa 100644
--- a/Libraries/LibGUI/Makefile
+++ b/Libraries/LibGUI/Makefile
@@ -41,7 +41,6 @@ OBJS = \
     GTreeView.o \
     GFileSystemModel.o \
     GFilePicker.o \
-    GDirectoryModel.o \
     GSplitter.o \
     GSpinBox.o \
     GGroupBox.o \