close #516

src/Shared/HandyControl_Shared/Controls/Panel/ElementGroup.cs

@@ -0,0 +1,120 @@
+using System.Collections.Generic;
+using System.Windows;
+using System.Windows.Controls;
+using HandyControl.Tools;
+
+namespace HandyControl.Controls
+{
+    public class ElementGroup : SimpleStackPanel
+    {
+        private static readonly Dictionary<Orientation, Dictionary<ChildLocation, CornerRadius>> CornerRadiusDict;
+
+        static ElementGroup()
+        {
+            var defaultCornerRadius = ResourceHelper.GetResourceInternal<CornerRadius>("DefaultCornerRadius");
+
+            CornerRadiusDict = new Dictionary<Orientation, Dictionary<ChildLocation, CornerRadius>>
+            {
+                [Orientation.Horizontal] = new()
+                {
+                    [ChildLocation.Single] = defaultCornerRadius,
+                    [ChildLocation.First] = new CornerRadius(defaultCornerRadius.TopLeft, 0, 0, defaultCornerRadius.BottomLeft),
+                    [ChildLocation.Middle] = new CornerRadius(),
+                    [ChildLocation.Last] = new CornerRadius(0, defaultCornerRadius.TopRight, defaultCornerRadius.BottomRight, 0)
+                },
+                [Orientation.Vertical] = new()
+                {
+                    [ChildLocation.Single] = defaultCornerRadius,
+                    [ChildLocation.First] = new CornerRadius(defaultCornerRadius.TopLeft, defaultCornerRadius.TopRight, 0, 0),
+                    [ChildLocation.Middle] = new CornerRadius(),
+                    [ChildLocation.Last] = new CornerRadius(0, 0, defaultCornerRadius.BottomRight, defaultCornerRadius.BottomLeft)
+                }
+            };
+        }
+
+        protected override void OnVisualChildrenChanged(DependencyObject visualAdded, DependencyObject visualRemoved)
+        {
+            base.OnVisualChildrenChanged(visualAdded, visualRemoved);
+
+            if (visualAdded is UIElement elementAdded)
+            {
+                elementAdded.GotFocus += ElementAdded_GotFocus;
+                elementAdded.LostFocus += ElementAdded_LostFocus;
+            }
+
+            if (visualRemoved is UIElement elementRemoved)
+            {
+                elementRemoved.GotFocus -= ElementAdded_GotFocus;
+                elementRemoved.LostFocus -= ElementAdded_LostFocus;
+            }
+
+            var childrenCount = InternalChildren.Count;
+            if (childrenCount == 0)
+            {
+                return;
+            }
+
+            var orientation = Orientation;
+
+            if (childrenCount == 1)
+            {
+                UpdateChildCornerRadius(InternalChildren[0], CornerRadiusDict[orientation][ChildLocation.Single]);
+            }
+            else
+            {
+                UpdateChildCornerRadius(InternalChildren[0], CornerRadiusDict[orientation][ChildLocation.First]);
+
+                var childMargin = orientation == Orientation.Horizontal
+                    ? new Thickness(-1, 0, 0, 0)
+                    : new Thickness(0, -1, 0, 0);
+
+                for (var childIndex = 1; childIndex < childrenCount; childIndex++)
+                {
+                    var child = InternalChildren[childIndex];
+                    child.SetCurrentValue(MarginProperty, childMargin);
+                    UpdateChildCornerRadius(child, CornerRadiusDict[orientation][ChildLocation.Middle]);
+                }
+
+                var lastChild = InternalChildren[childrenCount - 1];
+                lastChild.SetCurrentValue(MarginProperty, childMargin);
+                UpdateChildCornerRadius(lastChild, CornerRadiusDict[orientation][ChildLocation.Last]);
+            }
+        }
+
+        private static void UpdateChildCornerRadius(DependencyObject child, CornerRadius cornerRadius)
+        {
+            if (child is Border border)
+            {
+                border.SetCurrentValue(Border.CornerRadiusProperty, cornerRadius);
+            }
+            else
+            {
+                BorderElement.SetCornerRadius(child, cornerRadius);
+            }
+        }
+
+        private void ElementAdded_LostFocus(object sender, RoutedEventArgs e)
+        {
+            if (sender is UIElement element)
+            {
+                SetZIndex(element, 0);
+            }
+        }
+
+        private void ElementAdded_GotFocus(object sender, RoutedEventArgs e)
+        {
+            if (sender is UIElement element)
+            {
+                SetZIndex(element, int.MaxValue);
+            }
+        }
+
+        private enum ChildLocation
+        {
+            Single,
+            First,
+            Middle,
+            Last
+        }
+    }
+}