New controls, main view

src/Library/TerminalUI/Controls/ChildContainerView.cs

@@ -0,0 +1,58 @@
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+
+namespace TerminalUI.Controls;
+
+public abstract class ChildContainerView<T> : View<T>, IChildContainer<T>
+{
+    private readonly ObservableCollection<IView> _children = new();
+    public ReadOnlyObservableCollection<IView> Children { get; }
+    public ChildInitializer<T> ChildInitializer { get; }
+
+    protected ChildContainerView()
+    {
+        ChildInitializer = new ChildInitializer<T>(this);
+        Children = new ReadOnlyObservableCollection<IView>(_children);
+        _children.CollectionChanged += (o, args) =>
+        {
+            if (Attached)
+            {
+                if (args.NewItems?.OfType<IView>() is { } newItems)
+                {
+                    foreach (var newItem in newItems)
+                    {
+                        newItem.Attached = true;
+                    }
+                }
+
+                ApplicationContext?.EventLoop.RequestRerender();
+            }
+        };
+        
+        ((INotifyPropertyChanged)this).PropertyChanged += (o, args) =>
+        {
+            if (args.PropertyName == nameof(ApplicationContext))
+            {
+                foreach (var child in Children)
+                {
+                    child.ApplicationContext = ApplicationContext;
+                }
+            }
+        };
+    }
+
+    public override TChild AddChild<TChild>(TChild child)
+    {
+        child = base.AddChild(child);
+        _children.Add(child);
+        return child;
+    }
+
+    public override TChild AddChild<TChild, TDataContext>(TChild child, Func<T?, TDataContext?> dataContextMapper)
+        where TDataContext : default
+    {
+        child = base.AddChild(child, dataContextMapper);
+        _children.Add(child);
+        return child;
+    }
+}