big refactor and cleanup of dock + use tokio mpsc

examples/dock/dock_list/imp.rs

@@ -0,0 +1,33 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use glib::SignalHandlerId;
+use gtk4::subclass::prelude::*;
+use gtk4::{gio, glib};
+use gtk4::{Box, DragSource, DropTarget, GestureClick, ListView};
+use once_cell::sync::OnceCell;
+
+#[derive(Debug, Default)]
+pub struct DockList {
+    pub list_view: OnceCell<ListView>,
+    pub type_: OnceCell<super::DockListType>,
+    pub model: OnceCell<gio::ListStore>,
+    pub click_controller: OnceCell<GestureClick>,
+    pub drop_controller: OnceCell<DropTarget>,
+    pub drag_source: OnceCell<DragSource>,
+    pub drag_end_signal: Rc<RefCell<Option<SignalHandlerId>>>,
+    pub drag_cancel_signal: Rc<RefCell<Option<SignalHandlerId>>>,
+}
+
+#[glib::object_subclass]
+impl ObjectSubclass for DockList {
+    const NAME: &'static str = "DockList";
+    type Type = super::DockList;
+    type ParentType = Box;
+}
+
+impl ObjectImpl for DockList {}
+
+impl WidgetImpl for DockList {}
+
+impl BoxImpl for DockList {}