optimized menu style

src/Shared/HandyControl_Shared/Controls/Attach/MenuTopLineAttach.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
+using HandyControl.Tools;
+using HandyControl.Tools.Interop;
+
+namespace HandyControl.Controls
+{
+    public class MenuTopLineAttach
+    {
+        public static readonly DependencyProperty PopupProperty = DependencyProperty.RegisterAttached(
+            "Popup", typeof(Popup), typeof(MenuTopLineAttach), new PropertyMetadata(default(Popup), OnPopupChanged));
+
+        private static void OnPopupChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            var topLine = (FrameworkElement) d;
+
+            if (e.NewValue is Popup popup)
+            {
+                if (popup.TemplatedParent is MenuItem menuItem)
+                {
+                    SetTopLine(menuItem, topLine);
+                    menuItem.Unloaded += MenuItem_Unloaded;
+                } 
+                popup.Opened += Popup_Opened;
+            }
+        }
+
+        private static void MenuItem_Unloaded(object sender, RoutedEventArgs e)
+        {
+            var menuItem = (FrameworkElement)sender;
+            menuItem.Unloaded -= MenuItem_Unloaded;
+            var topLine = GetTopLine(menuItem);
+            var popup = GetPopup(topLine);
+            if (popup != null)
+            {
+                popup.Opened -= Popup_Opened;
+            }
+        }
+
+        private static void Popup_Opened(object sender, EventArgs e)
+        {
+            var popup = (Popup) sender;
+            if (popup.TemplatedParent is MenuItem menuItem)
+            {
+                var topLine = GetTopLine(menuItem);
+                if (topLine == null) return;
+
+                topLine.HorizontalAlignment = HorizontalAlignment.Left;
+                topLine.Width = menuItem.ActualWidth;
+                topLine.Margin = new Thickness();
+
+                var positionLeftTop = menuItem.PointToScreen(new Point());
+                var positionRightBottom = menuItem.PointToScreen(new Point(menuItem.ActualWidth, menuItem.ActualHeight));
+                ScreenHelper.FindMonitorRectsFromPoint(InteropMethods.GetCursorPos(), out _, out var workAreaRect);
+                var panel = VisualHelper.GetParent<Panel>(topLine);
+
+                if (positionLeftTop.X < 0)
+                {
+                    
+                    topLine.Margin = new Thickness(positionLeftTop.X - panel.Margin.Left, 0, 0, 0);
+                }
+                else if (positionLeftTop.X + panel.ActualWidth > workAreaRect.Right)
+                {
+                    var overflowWidth = positionRightBottom.X - workAreaRect.Right;
+                    if (overflowWidth > 0)
+                    {
+                        topLine.Width -= overflowWidth + panel.Margin.Right;
+                    }
+                    topLine.HorizontalAlignment = HorizontalAlignment.Left;
+                    topLine.Margin = new Thickness(positionLeftTop.X + panel.ActualWidth - workAreaRect.Right + panel.Margin.Right, 0, 0, 0);
+                }
+
+                if (positionRightBottom.Y > workAreaRect.Bottom)
+                {
+                    topLine.Width = 0;
+                    topLine.HorizontalAlignment = HorizontalAlignment.Stretch;
+                    topLine.Margin = new Thickness();
+                }
+            }
+        }
+
+        public static void SetPopup(DependencyObject element, Popup value)
+            => element.SetValue(PopupProperty, value);
+
+        public static Popup GetPopup(DependencyObject element)
+            => (Popup) element.GetValue(PopupProperty);
+
+        internal static readonly DependencyProperty TopLineProperty = DependencyProperty.RegisterAttached(
+            "TopLine", typeof(FrameworkElement), typeof(MenuTopLineAttach), new PropertyMetadata(default(FrameworkElement)));
+
+        internal static void SetTopLine(DependencyObject element, FrameworkElement value)
+            => element.SetValue(TopLineProperty, value);
+
+        internal static FrameworkElement GetTopLine(DependencyObject element)
+            => (FrameworkElement) element.GetValue(TopLineProperty);
+    }
+}