优化拖放逻辑和计算方法

在 `DockTargetButton.xaml.cs` 中，重构了 `OnDragEnter` 方法，简化了逻辑，提升了可读性。现在根据 `Target` 类型处理拖动预览。

在 `LayoutPanel.xaml.cs` 中，简化了 `CalculateHeight` 和 `CalculateWidth` 方法的返回逻辑，使用三元运算符替代了原有的 `if` 语句，使代码更加简洁。

Author: qian-o

src/WinUI.Dock/Controls/DockTargetButton.xaml.cs

@@ -37,18 +37,18 @@ protected override async void OnDragEnter(DragEventArgs e)
     {
         base.OnDragEnter(e);
 
-        string dragKey = (string)await e.DataView.GetDataAsync(DragDropHelpers.FormatId);
-
-        if (DragDropHelpers.GetDocument(dragKey) is Document document)
+        if (Target is DockManager dockManager)
         {
-            if (Target is DockManager dockManager)
+            string dragKey = (string)await e.DataView.GetDataAsync(DragDropHelpers.FormatId);
+
+            if (DragDropHelpers.GetDocument(dragKey) is Document document)
             {
                 dockManager.ShowDockPreview(document, DockTarget);
             }
-            else if (Target is DocumentGroup documentGroup)
-            {
-                documentGroup.ShowDockPreview(DockTarget);
-            }
+        }
+        else if (Target is DocumentGroup documentGroup)
+        {
+            documentGroup.ShowDockPreview(DockTarget);
         }
     }
 

src/WinUI.Dock/LayoutPanel.xaml.cs

@@ -125,12 +125,7 @@ internal double CalculateHeight(DockModule module, bool isStar)
         double totalHeight = children.Sum(static item => double.IsNaN(item.DockHeight) ? 1.0 : item.DockHeight);
         double moduleHeight = double.IsNaN(module.DockHeight) ? totalHeight / children.Length : module.DockHeight;
 
-        if (isStar)
-        {
-            return moduleHeight;
-        }
-
-        return ActualHeight / totalHeight * moduleHeight;
+        return isStar ? moduleHeight : ActualHeight / totalHeight * moduleHeight;
     }
 
     internal double CalculateWidth(DockModule module, bool isStar)
@@ -140,11 +135,6 @@ internal double CalculateWidth(DockModule module, bool isStar)
         double totalWidth = children.Sum(static item => double.IsNaN(item.DockWidth) ? 1.0 : item.DockWidth);
         double moduleWidth = double.IsNaN(module.DockWidth) ? totalWidth / children.Length : module.DockWidth;
 
-        if (isStar)
-        {
-            return moduleWidth;
-        }
-
-        return ActualWidth / totalWidth * moduleWidth;
+        return isStar ? moduleWidth : ActualWidth / totalWidth * moduleWidth;
     }
 }