GTK/Vala 开发教程：图形界面架构与异步线程模型

public class LivePhotoConv.Application : Adw.Application {

construct {
    application_id = "com.github.wszqkzqk.live-photo-conv";
    flags = ApplicationFlags.DEFAULT_FLAGS;
}

var style_manager = Adw.StyleManager.get_default ();
string init_scheme;
switch (style_manager.color_scheme) {
    case FORCE_LIGHT: init_scheme = "force-light"; break;
    case FORCE_DARK:  init_scheme = "force-dark";  break;
    default:          init_scheme = "default";      break;
}

var scheme_action = new SimpleAction.stateful ("color-scheme", VariantType.STRING,
    new Variant.string (init_scheme));
scheme_action.notify["state"].connect (() => {
    style_manager.color_scheme = scheme_action.state.get_string () switch {
        "force-light" => Adw.ColorScheme.FORCE_LIGHT,
        "force-dark"  => Adw.ColorScheme.FORCE_DARK,
        default       => Adw.ColorScheme.DEFAULT,
    };
});
add_action (scheme_action);

var about_action = new SimpleAction ("about", null);
about_action.activate.connect (show_about);
add_action (about_action);

var about = new Adw.AboutDialog () {
    application_name = "Live Photo Converter",
    application_icon = "com.github.wszqkzqk.live-photo-conv",
    developer_name = "Zhou Qiankang",
    developers = { "Zhou Qiankang <wszqkzqk@qq.com>" },
    copyright = COPYRIGHT,
    license_type = Gtk.License.LGPL_2_1,
    version = VERSION,
    website = WEBSITE,
    issue_url = ISSUES_URL,
};
about.present (active_window);

private class LivePhotoConv.FileDropArea : Adw.Bin {
    public signal void changed ();

public string hint { get; construct; }
public string icon_name { get; construct; default = "document-open-symbolic"; }
public string[] mime_types { get; construct; default = new string[0]; }

public FileDropArea (string hint, string? icon_name = null, string[]? mime_types = null) {
    Object (hint: hint, icon_name: icon_name ?? "document-open-symbolic",
            mime_types: mime_types ?? new string[0]);
}

public GenericArray<File> files {
    get { return _files; }
    set {
        _files = value;
        if (value.length == 0) {
            label_stack.visible_child = hint_label;
            icon_image.icon_name = _orig_icon;
            icon_image.opacity = 0.5;
        } else if (value.length == 1) {
            file_label.label = value[0].get_basename ();
            label_stack.visible_child = file_label;
            icon_image.icon_name = "emblem-documents-symbolic";
            icon_image.opacity = 1.0;
        } else {
            file_label.label = ngettext ("%u file selected", "%u files selected", value.length).printf (value.length);
            label_stack.visible_child = file_label;
            icon_image.icon_name = "emblem-documents-symbolic";
            icon_image.opacity = 1.0;
        }
        changed ();
    }
}

var drop_target = new Gtk.DropTarget (Type.INVALID, Gdk.DragAction.COPY);
drop_target.set_gtypes ({typeof (Gdk.FileList), typeof (File)});
drop_target.drop.connect (on_drop);
this.add_controller (drop_target);

private bool on_drop (Value value, double x, double y) {
    var collected = new GenericArray<File> ();
    if (value.holds (typeof (Gdk.FileList))) {
        foreach (var file in ((Gdk.FileList) value.get_object ()).get_files ())
            collected.add (file);
    } else if (value.holds (typeof (File))) {
        collected.add (value.get_object () as File);
    }
    load_files (collected);
    return true;
}

var click = new Gtk.GestureClick ();
click.pressed.connect (on_clicked);
this.add_controller (click);

var header = new Adw.HeaderBar ();
var view_switcher = new Adw.ViewSwitcher ();
var stack = new Adw.ViewStack ();
view_switcher.stack = stack;

stack.add_titled_with_icon (page_with_action_button (build_extract_page (), extract_button), 
    "extract", _("Extract"), "document-send-symbolic");
stack.add_titled_with_icon (page_with_action_button (build_make_page (), make_button), 
    "make", _("Make"), "list-add-symbolic");
stack.add_titled_with_icon (page_with_action_button (build_repair_page (), repair_button), 
    "repair", _("Repair"), "applications-utilities-symbolic");

header.title_widget = view_switcher;

private Gtk.Widget page_with_action_button (Gtk.Widget content, Gtk.Button button) {
    var scroll = new Gtk.ScrolledWindow () {
        child = content,
        vexpand = true, hexpand = true,
    };
    var box = new Gtk.Box (Gtk.Orientation.VERTICAL, 0);
    box.append (scroll);
    box.append (button);
    return box;
}

private Adw.PreferencesGroup make_group (string title, string? description = null);

private Adw.ActionRow make_check_row (string title, out Gtk.CheckButton out_check,
                                        bool active = true, string? tooltip = null);

private Adw.ActionRow make_entry_row (string title, out Gtk.Entry out_entry,
                                        string? placeholder = null);

private Adw.ActionRow make_check_row (string title, out Gtk.CheckButton out_check, ...) {
    var check = new Gtk.CheckButton () { ... };
    out_check = check;
    var row = new Adw.ActionRow () { title = title, activatable = false, ... };
    row.add_suffix (check);
    return row;
}

options_group.add (make_check_row (_("Export main image"), out extract_main_image_check, true));

private async void extract_batch_async (File[] files, File dest_dir, ..., Gtk.Button button)
                                       throws ExportError, NotLivePhotosError {
    // 第一步：捕获回调
    SourceFunc callback = extract_batch_async.callback;

    // 第二步：启动工作线程
    bool success;
    int error_count;
    StringBuilder error_sb;
    new Thread<void> ("extract-batch", () => {
        // 在后台线程中逐个处理文件
        for (int i = 0; i < files.length; i++) {
            // ... 处理逻辑 ...
            // 第三步：通过 Idle 向主线程报告进度
            Idle.add (() => {
                report_progress (button, _("Extracting"), processed, total);
                return false;
            });
        }
        // 第四步：工作完成，唤醒主线程
        Idle.add ((owned) callback);
    });

    // 第五步：挂起协程，等待工作线程完成
    yield;

    // 回到主线程，处理结果
    if (error_count > 0)
        throw new ExportError.FILE_PUSH_ERROR (...);
}

var sb = new StringBuilder ();
// ... 处理失败时:
sb.append_printf ("%s: %s\n", file.get_basename (), e.message);
error_count++;

if (error_count > 0) {
    if (error_count != total)
        throw new ExportError.FILE_PUSH_ERROR (
            "%u of %u files failed:\n%s".printf ((uint) error_count, (uint) total, sb.str));
    else
        throw new ExportError.FILE_PUSH_ERROR (sb.str);
}

private void start_work (Gtk.Button button, string label) {
    working = true;
    button.sensitive = false;
    button.label = label;
}

private void end_work (Gtk.Button button, string label, bool sensitive) {
    working = false;
    button.label = label;
    button.sensitive = sensitive;
}

private static void report_progress (Gtk.Button button, string verb,
                                      int current, int total) {
    button.label = @"$(verb) $(current)/$(total)…";
}

private void show_error_dialog (string title, string detail) {
    var dialog = new Adw.AlertDialog (title, detail);
    dialog.add_response ("ok", "OK");
    dialog.present (active_window);
}

private void show_toast (string msg) {
    toast_overlay.add_toast (new Adw.Toast (msg) { timeout = 3 });
}