更新

WPFDark/Controls/Internals/FrameworkElementBag.cs

@@ -0,0 +1,122 @@
+using System.Collections.Generic;
+using System.Windows;
+using System.Windows.Media;
+
+namespace WPFDark.Controls.Internals
+{
+    internal class FrameworkElementBag<T> : FrameworkElement
+        where T : FrameworkElement
+    {
+        internal IReadOnlyList<T> Children => _children;
+        
+        private readonly List<T> _children = new List<T>();
+        private readonly HashSet<T> _childrenForSearch = new HashSet<T>();
+        private readonly HashSet<T> _changedElements = new HashSet<T>();
+
+        static FrameworkElementBag()
+        {
+            DefaultStyleKeyProperty.OverrideMetadata(typeof(FrameworkElementBag<T>),
+                new FrameworkPropertyMetadata(typeof(FrameworkElementBag<T>)));
+        }
+
+        internal FrameworkElementBag(IHasTransform transform)
+        {
+            var g = new TransformGroup();
+            g.Children.Add(transform.ScaleTransform);
+            g.Children.Add(transform.TranslateTransform);
+            RenderTransform = g;
+        }
+
+        internal void AddChild(T child)
+        {
+            if (_childrenForSearch.Contains(child))
+                return;
+
+            _children.Add(child);
+            _childrenForSearch.Add(child);
+
+            AddVisualChild(child);
+            ChangeElement(child);
+        }
+
+        internal void RemoveChild(T child)
+        {
+            if (_childrenForSearch.Contains(child) == false)
+                return;
+
+            _children.Remove(child);
+            _childrenForSearch.Remove(child);
+
+            RemoveVisualChild(child);
+
+            child.Width = double.NaN;
+            child.Height = double.NaN;
+        }
+
+        internal void ToLast(T child)
+        {
+            if (_childrenForSearch.Contains(child) == false)
+                return;
+
+            if (_children.Count == 0)
+                return;
+
+            if (Equals(_children[_children.Count - 1], child))
+                return;
+
+            _children.Remove(child);
+            RemoveVisualChild(child);
+
+            _children.Add(child);
+            AddVisualChild(child);
+
+            ChangeElement(child);
+        }
+
+        internal void ChangeElement(T child)
+        {
+            if (_isInMeasureOverride)
+                return;
+
+            _changedElements.Add(child);
+        }
+
+        protected override int VisualChildrenCount => _children.Count;
+
+        protected override Visual GetVisualChild(int index) => _children[index];
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            ArrangeChildren(_changedElements);
+
+            _changedElements.Clear();
+
+            return base.ArrangeOverride(finalSize);
+        }
+
+        private bool _isInMeasureOverride;
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            _isInMeasureOverride = true;
+
+            MeasureChildren(_changedElements, availableSize);
+
+            _isInMeasureOverride = false;
+
+            return base.MeasureOverride(availableSize);
+        }
+
+        protected virtual void ArrangeChildren(IEnumerable<T> children)
+        {
+            foreach (var child in children)
+                child.Arrange(new Rect(new Point(), child.DesiredSize));
+        }
+
+        protected virtual void MeasureChildren(IEnumerable<T> children, Size availableSize)
+        {
+            foreach (var child in children)
+                child.Measure(availableSize);
+        }
+    }
+}