Merge pull request #4301 from AvaloniaUI/fixes/more-relative-panel-fixes

Fixes/more relative panel fixes

src/Avalonia.Controls/RelativePanel.cs

@@ -54,7 +54,7 @@ namespace Avalonia.Controls
             }
             _childGraph.Measure(availableSize);
 
-            _childGraph.Reset();
+            _childGraph.Reset(false);
             var boundingSize = _childGraph.GetBoundingSize(Width.IsNaN(), Height.IsNaN());
             _childGraph.Reset();
             _childGraph.Measure(boundingSize);
@@ -119,17 +119,22 @@ namespace Avalonia.Controls
 
             public void Arrange(Size arrangeSize) => Element.Arrange(new Rect(Left, Top, Math.Max(arrangeSize.Width - Left - Right, 0), Math.Max(arrangeSize.Height - Top - Bottom, 0)));
 
-            public void Reset()
+            public void Reset(bool clearPos)
             {
-                Left = double.NaN;
-                Top = double.NaN;
-                Right = double.NaN;
-                Bottom = double.NaN;
+                if (clearPos)
+                {
+                    Left = double.NaN;
+                    Top = double.NaN;
+                    Right = double.NaN;
+                    Bottom = double.NaN;
+                }
+
                 Measured = false;
             }
 
             public Size GetBoundingSize()
             {
+                if (Left < 0 || Top < 0) return default;
                 if (Measured)
                     return BoundingSize;
 
@@ -209,7 +214,7 @@ namespace Avalonia.Controls
                 _nodeDic.Clear();
             }
 
-            public void Reset() => _nodeDic.Values.Do(node => node.Reset());
+            public void Reset(bool clearPos = true) => _nodeDic.Values.Do(node => node.Reset(clearPos));
 
             public GraphNode? AddLink(GraphNode from, Layoutable? to)
             {
@@ -255,28 +260,21 @@ namespace Avalonia.Controls
 
                 foreach (var node in nodes)
                 {
-                    /*
-                     * 该节点无任何依赖，所以从这里开始计算元素位置。
-                     * 因为无任何依赖，所以忽略同级元素
-                     */
                     if (!node.Measured && !node.OutgoingNodes.Any())
                     {
                         MeasureChild(node);
                         continue;
                     }
-
-                    //  判断依赖元素是否全部排列完毕
+                    
                     if (node.OutgoingNodes.All(item => item.Measured))
                     {
                         MeasureChild(node);
                         continue;
                     }
-
-                    //  判断是否有循环
+                    
                     if (!set.Add(node.Element))
                         throw new Exception("RelativePanel error: Circular dependency detected. Layout could not complete.");
-
-                    //  没有循环，且有依赖，则继续往下
+                    
                     Measure(node.OutgoingNodes, set);
 
                     if (!node.Measured)

tests/Avalonia.Controls.UnitTests/RelativePanelTests.cs

@@ -82,5 +82,55 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(new Rect(0, 0, 20, 20), target.Children[0].Bounds);
             Assert.Equal(new Rect(0, 20, 20, 20), target.Children[1].Bounds);
         }
+
+        [Fact]
+        public void LeftOf_Measures_Correctly()
+        {
+            var rect1 = new Rectangle { Height = 20, Width = 20 };
+            var rect2 = new Rectangle { Height = 20, Width = 20 };
+
+            var target = new RelativePanel
+            {
+                VerticalAlignment = Layout.VerticalAlignment.Center,
+                HorizontalAlignment = Layout.HorizontalAlignment.Center,
+                Children =
+                {
+                    rect1, rect2
+                }
+            };
+
+            RelativePanel.SetLeftOf(rect2, rect1);
+            target.Measure(new Size(400, 400));
+            target.Arrange(new Rect(target.DesiredSize));
+
+            Assert.Equal(new Size(20, 20), target.Bounds.Size);
+            Assert.Equal(new Rect(0, 0, 20, 20), target.Children[0].Bounds);
+            Assert.Equal(new Rect(-20, 0, 20, 20), target.Children[1].Bounds);
+        }
+
+        [Fact]
+        public void Above_Measures_Correctly()
+        {
+            var rect1 = new Rectangle { Height = 20, Width = 20 };
+            var rect2 = new Rectangle { Height = 20, Width = 20 };
+
+            var target = new RelativePanel
+            {
+                VerticalAlignment = Layout.VerticalAlignment.Center,
+                HorizontalAlignment = Layout.HorizontalAlignment.Center,
+                Children =
+                {
+                    rect1, rect2
+                }
+            };
+
+            RelativePanel.SetAbove(rect2, rect1);
+            target.Measure(new Size(400, 400));
+            target.Arrange(new Rect(target.DesiredSize));
+
+            Assert.Equal(new Size(20, 20), target.Bounds.Size);
+            Assert.Equal(new Rect(0, 0, 20, 20), target.Children[0].Bounds);
+            Assert.Equal(new Rect(0, -20, 20, 20), target.Children[1].Bounds);
+        }
     }
 }