feat: SectionPanel ChildrenSource and ChildrenTemplate

GSS2.UI.Core/SectionPanel.cs

@@ -1,6 +1,10 @@
+using System.Collections;
+using System.Collections.Specialized;
+
 using Avalonia;
 using Avalonia.Animation;
 using Avalonia.Controls;
+using Avalonia.Controls.Templates;
 using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Styling;
@@ -64,6 +68,18 @@ public class SectionPanel : Panel
         get => GetValue(CanScrollBackwardProperty);
         set => SetValue(CanScrollBackwardProperty, value);
     }
+    public static readonly StyledProperty<IEnumerable?> ChildrenSourceProperty = AvaloniaProperty.Register<SectionPanel, IEnumerable?>(nameof(ChildrenSource), null, defaultBindingMode: Avalonia.Data.BindingMode.OneWay);
+    public IEnumerable? ChildrenSource
+    {
+        get => GetValue(ChildrenSourceProperty);
+        set => SetValue(ChildrenSourceProperty, value);
+    }
+    public static readonly StyledProperty<IDataTemplate?> ChildrenTemplateProperty = AvaloniaProperty.Register<ItemsControl, IDataTemplate?>(nameof(ChildrenTemplate), null);
+    public IDataTemplate? ChildrenTemplate
+    {
+        get => GetValue(ChildrenTemplateProperty);
+        set => SetValue(ChildrenTemplateProperty, value);
+    }
 
     private readonly Dictionary<Control, int> _childIndeces = new Dictionary<Control, int>();
     private bool _initialized = false;
@@ -78,13 +94,153 @@ public class SectionPanel : Panel
             CanScrollBackward = Cyclic || CurrentIndex != 0;
             panel.InvalidateArrange();
         });
+        ChildrenSourceProperty.Changed.AddClassHandler<SectionPanel>((panel, ea) =>
+        {
+            if (panel != this)
+                return;
+            (ea.OldValue as INotifyCollectionChanged)?.CollectionChanged -= panel.OnChildrenSourceCollectionChanged;
+            (ea.NewValue as INotifyCollectionChanged)?.CollectionChanged += panel.OnChildrenSourceCollectionChanged;
+            panel.Children.Clear();
+            if (ea.NewValue is IEnumerable enumerable)
+            {
+                IEnumerable<Control> controls;
+                if (ChildrenTemplate is null)
+                    controls = enumerable.OfType<Control>();
+                else
+                    controls = enumerable.Cast<object?>()
+                        .Where(ChildrenTemplate.Match)
+                        .Select(i =>
+                        {
+                            var control = ChildrenTemplate.Build(i);
+                            control?.DataContext = i;
+                            return control;
+                        })
+                        .OfType<Control>();
+
+                foreach (var control in controls)
+                    panel.Children.Add(control);
+            }
+            panel.InvalidateArrange();
+        });
         Children.CollectionChanged += (_, ea) =>
         {
-            CanScrollForward = Cyclic || CurrentIndex != Children.Count() - 1;
+            CanScrollForward = (Cyclic && Children.Count() > 1) || CurrentIndex != Children.Count() - 1;
-            CanScrollBackward = Cyclic || CurrentIndex != 0;
+            CanScrollBackward = (Cyclic && Children.Count() > 1) || CurrentIndex != 0;
         };
     }
 
+    protected void OnChildrenSourceCollectionChanged(object? sender, NotifyCollectionChangedEventArgs ea)
+    {
+        switch (ea.Action)
+        {
+            case NotifyCollectionChangedAction.Add:
+                {
+                    if (ea.NewItems is null)
+                        return;
+
+                    var index = ea.NewStartingIndex >= 0
+                        ? ea.NewStartingIndex
+                        : Children.Count;
+
+                    IEnumerable<Control> controls;
+                    if (ChildrenTemplate is null)
+                        controls = ea.NewItems.OfType<Control>();
+                    else
+                        controls = ea.NewItems.Cast<object?>()
+                            .Where(ChildrenTemplate.Match)
+                            .Select(i =>
+                            {
+                                var control = ChildrenTemplate.Build(i);
+                                control?.DataContext = i;
+                                return control;
+                            })
+                            .OfType<Control>();
+
+                    foreach (Control control in controls)
+                        Children.Insert(index++, control);
+
+
+                    break;
+                }
+
+            case NotifyCollectionChangedAction.Remove:
+                {
+                    if (ea.OldItems is null)
+                        return;
+
+                    foreach (Control control in ea.OldItems)
+                        Children.Remove(control);
+
+                    break;
+                }
+
+            case NotifyCollectionChangedAction.Replace:
+                {
+                    if (ea.OldItems is not null)
+                        foreach (Control control in ea.OldItems)
+                            Children.Remove(control);
+
+                    if (ea.NewItems is not null)
+                    {
+                        var index = ea.NewStartingIndex >= 0 ?
+                            ea.NewStartingIndex :
+                            Children.Count;
+
+                        foreach (Control control in ea.NewItems)
+                            Children.Insert(index++, control);
+                    }
+
+                    break;
+                }
+
+            case NotifyCollectionChangedAction.Move:
+                {
+                    if (ea.OldItems is not IEnumerable<Control> oldControls || oldControls.Count() == 0)
+                        return;
+
+                    var control = oldControls.First();
+
+                    if (ea.OldStartingIndex >= 0)
+                        Children.RemoveAt(ea.OldStartingIndex);
+
+                    if (ea.NewStartingIndex >= 0)
+                        Children.Insert(ea.NewStartingIndex, control);
+
+                    break;
+                }
+
+            case NotifyCollectionChangedAction.Reset:
+                {
+                    Children.Clear();
+
+                    if (ChildrenSource is null)
+                        break;
+
+                    IEnumerable<Control> controls;
+                    if (ChildrenTemplate is null)
+                        controls = ChildrenSource.OfType<Control>();
+                    else
+                        controls = ChildrenSource.Cast<object?>()
+                            .Where(ChildrenTemplate.Match)
+                            .Select(i =>
+                            {
+                                var control = ChildrenTemplate.Build(i);
+                                control?.DataContext = i;
+                                return control;
+                            })
+                            .OfType<Control>();
+
+                    foreach (var control in controls)
+                        Children.Add(control);
+
+                    break;
+                }
+        }
+
+        InvalidateMeasure();
+        InvalidateArrange();
+    }
+
     protected override Size MeasureOverride(Size availableSize)
     {
         foreach (var child in Children)