Ensured zoom control invalidates adorner layer

Westermo.GraphX.Controls.Avalonia.Tests/ZoomControlAdornerLayerTests.cs

@@ -0,0 +1,175 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Markup.Xaml.Templates;
+using Avalonia.Media;
+using QuikGraph;
+using Westermo.GraphX.Common.Models;
+using Westermo.GraphX.Controls.Controls;
+using Westermo.GraphX.Controls.Controls.ZoomControl;
+using Westermo.GraphX.Controls.Controls.ZoomControl.SupportClasses;
+using Westermo.GraphX.Logic.Models;
+
+namespace Westermo.GraphX.Controls.Avalonia.Tests;
+
+/// <summary>
+/// Regression tests for adorners attached to <see cref="VertexControl"/>s while the hosting
+/// <see cref="ZoomControl"/> is zoomed or panned.
+///
+/// Avalonia's <c>AdornerLayer</c> bakes <c>adornedElement.TransformToVisual(layer)</c> into each
+/// adorner's <c>RenderTransform</c> during its own arrange pass, and only re-runs that pass when
+/// it observes a <c>RenderTransform</c>/<c>Bounds</c> change on the adorned element or an ancestor.
+/// Since the ZoomControl mutates its presenter's scale/translate transforms in place (no property
+/// change is raised), it must explicitly invalidate the adorner layer - otherwise adorners stay
+/// frozen at their pre-zoom screen position while the vertex moves underneath them.
+/// </summary>
+public class ZoomControlAdornerLayerTests
+{
+    private const double Tolerance = 0.5;
+
+    private class TVertex(string name) : VertexBase
+    {
+        public string Name { get; } = name;
+        public override string ToString() => Name;
+    }
+
+    private class TEdge(TVertex s, TVertex t) : EdgeBase<TVertex>(s, t)
+    {
+        public override Westermo.GraphX.Measure.Point[]? RoutingPoints { get; set; }
+    }
+
+    /// <summary>
+    /// Gives the vertex control a minimal template so it can be measured/arranged headlessly.
+    /// </summary>
+    private static void EnsureVertexTemplate(VertexControl vc)
+    {
+        if (vc.Template != null) return;
+        var content = new Grid();
+        var panel = new StackPanel { Name = "PART_vcproot" };
+        content.Children.Add(panel);
+        var ns = new NameScope();
+        ns.Register("PART_vcproot", panel);
+        var functor = new Func<IServiceProvider?, object?>(_ => new TemplateResult<Control>(content, ns));
+        vc.Template = new ControlTemplate { TargetType = typeof(VertexControl), Content = functor };
+        vc.ApplyTemplate();
+    }
+
+    /// <summary>
+    /// Builds a window containing a ZoomControl hosting a GraphArea with a single vertex placed
+    /// away from the origin, plus an adorner attached to that vertex via the adorner layer.
+    /// </summary>
+    private static (Window window, ZoomControl zoom, VertexControl vertex, Control adorner) CreateScene()
+    {
+        var g = new BidirectionalGraph<TVertex, TEdge>();
+        var v1 = new TVertex("Root");
+        g.AddVertex(v1);
+
+        var lc = new GXLogicCore<TVertex, TEdge, BidirectionalGraph<TVertex, TEdge>> { Graph = g };
+        var area = new GraphArea<TVertex, TEdge, BidirectionalGraph<TVertex, TEdge>> { LogicCore = lc };
+        area.PreloadVertexes();
+
+        var vc = area.VertexList[v1];
+        vc.Width = 64;
+        vc.Height = 64;
+        EnsureVertexTemplate(vc);
+        vc.SetPosition(500, 300);
+        GraphAreaBase.SetFinalX(vc, 500);
+        GraphAreaBase.SetFinalY(vc, 300);
+
+        var zc = new ZoomControl { Content = area, Mode = ZoomControlModes.Custom };
+        // The headless test app has no window theme, so no VisualLayerManager (and therefore no
+        // adorner layer) is created by the Window's template. Host one explicitly so the scene
+        // matches a real themed application.
+        var layerManager = new VisualLayerManager { Child = zc };
+        var window = new Window { Width = 800, Height = 600, Content = layerManager };
+        window.Show();
+        window.Measure(new Size(800, 600));
+        window.Arrange(new Rect(0, 0, 800, 600));
+        window.UpdateLayout();
+
+        // An adorner with no explicit size is arranged to exactly cover the adorned element, so
+        // its local coordinate space coincides with the vertex's: a correctly positioned adorner
+        // maps every local point to the same root coordinate as the vertex does.
+        var adorner = new Border { Background = Brushes.Red };
+        AdornerLayer.SetAdorner(vc, adorner);
+        window.UpdateLayout();
+
+        return (window, zc, vc, adorner);
+    }
+
+    /// <summary>
+    /// Returns the offset (in root/window coordinates) between the adorner and the vertex for the
+    /// given point expressed in their shared local coordinate space. A correctly tracking adorner
+    /// yields (0,0) for every point, at any zoom level and pan offset.
+    /// </summary>
+    private static Point OffsetInRoot(Visual root, Visual vertex, Visual adorner, Point localPoint)
+    {
+        var vertexPoint = vertex.TranslatePoint(localPoint, root) ?? default;
+        var adornerPoint = adorner.TranslatePoint(localPoint, root) ?? default;
+        return adornerPoint - vertexPoint;
+    }
+
+    /// <summary>
+    /// Asserts that the adorner is exactly aligned with the adorned vertex, checking both the
+    /// origin (catches lost translation) and the far corner (catches lost scale).
+    /// </summary>
+    private static async Task AssertAdornerAlignedAsync(Window window, VertexControl vc, Control adorner,
+        string phase)
+    {
+        var origin = OffsetInRoot(window, vc, adorner, new Point(0, 0));
+        var corner = OffsetInRoot(window, vc, adorner, new Point(vc.Width, vc.Height));
+        Console.WriteLine($"{phase}: originOffset={origin} cornerOffset={corner}");
+
+        await Assert.That(origin.X).IsEqualTo(0).Within(Tolerance);
+        await Assert.That(origin.Y).IsEqualTo(0).Within(Tolerance);
+        await Assert.That(corner.X).IsEqualTo(0).Within(Tolerance);
+        await Assert.That(corner.Y).IsEqualTo(0).Within(Tolerance);
+    }
+
+    [Test]
+    public async Task PanningZoomControl_KeepsAdornerAlignedWithVertex()
+    {
+        var (window, zc, vc, adorner) = CreateScene();
+
+        await AssertAdornerAlignedAsync(window, vc, adorner, "before pan");
+
+        // Pure pan: no content-extent change, so nothing else invalidates the adorner layer.
+        zc.TranslateX += 75;
+        zc.TranslateY += 40;
+        window.UpdateLayout();
+
+        await AssertAdornerAlignedAsync(window, vc, adorner, "after pan");
+    }
+
+    [Test]
+    public async Task ZoomingZoomControl_KeepsAdornerAlignedWithVertex()
+    {
+        var (window, zc, vc, adorner) = CreateScene();
+
+        await AssertAdornerAlignedAsync(window, vc, adorner, "before zoom");
+
+        zc.Zoom *= 2;
+        window.UpdateLayout();
+
+        await AssertAdornerAlignedAsync(window, vc, adorner, "after zoom");
+    }
+
+    [Test]
+    public async Task ZoomToFill_KeepsAdornerAlignedWithVertex()
+    {
+        var (window, zc, vc, adorner) = CreateScene();
+
+        await AssertAdornerAlignedAsync(window, vc, adorner, "before fill");
+
+        zc.ZoomToFill();
+        window.UpdateLayout();
+        await AssertAdornerAlignedAsync(window, vc, adorner, "after first fill");
+
+        // A second fill is a no-op for the content extent, so only the zoom/translate transform
+        // mutation can keep the adorner in sync.
+        zc.ZoomToFill();
+        window.UpdateLayout();
+        await AssertAdornerAlignedAsync(window, vc, adorner, "after second fill");
+    }
+}

Westermo.GraphX.Controls.Avalonia/Controls/ZoomControl/ZoomControl.cs

@@ -67,6 +67,37 @@ private void ScheduleViewportUpdate()
         }, DispatcherPriority.Render);
     }
 
+    /// <summary>
+    /// Notifies the visual/layout system that the presenter's render transform was changed.
+    /// </summary>
+    /// <remarks>
+    /// The scale/translate transforms are mutated in place (deliberately - reallocating a
+    /// <see cref="TransformGroup"/> on every pan/zoom tick would churn the heap during drag
+    /// operations). In-place mutation raises neither <see cref="Visual.RenderTransformProperty"/>
+    /// nor <see cref="Visual.BoundsProperty"/>, which are the only signals Avalonia's
+    /// <c>AdornerHelper</c> listens for when deciding to re-arrange the adorner layer.
+    ///
+    /// The adorner layer positions each adorner by baking
+    /// <c>adornedElement.TransformToVisual(layer)</c> into the adorner's render transform during
+    /// its own arrange pass, so without an explicit invalidation any adorner attached to a
+    /// <c>VertexControl</c> would stay frozen at its pre-zoom screen position while the vertex
+    /// moves and scales underneath it. Invalidating the layer's arrange is far cheaper than
+    /// invalidating the presenter subtree's layout, and leaves the graph content itself
+    /// untouched (it only needs a repaint, which <see cref="Visual.InvalidateVisual"/> covers).
+    /// </remarks>
+    private void InvalidatePresenterTransform(bool invalidateVisual = true)
+    {
+        var presenter = _presenter;
+        if (presenter == null) return;
+
+        if (invalidateVisual) presenter.InvalidateVisual();
+
+        var adornerLayer = AdornerLayer.GetAdornerLayer(presenter);
+        if (adornerLayer == null || adornerLayer.Children.Count == 0) return;
+        adornerLayer.InvalidateMeasure();
+        adornerLayer.InvalidateArrange();
+    }
+
     /// <summary>
     /// Notifies the contained GraphArea of viewport changes for culling optimization.
     /// </summary>
@@ -320,7 +351,7 @@ private static void TranslateX_PropertyChanged(ZoomControl zc, AvaloniaPropertyC
         zc._translateTransform.X = (double)e.NewValue!;
         if (!zc._isZooming) zc.Mode = ZoomControlModes.Custom;
         zc.OnPropertyChanged(nameof(Presenter));
-        if (!zc._isZooming) zc.Presenter?.InvalidateVisual();
+        zc.InvalidatePresenterTransform(!zc._isZooming);
         zc.ScheduleViewportUpdate();
     }
 
@@ -330,7 +361,7 @@ private static void TranslateY_PropertyChanged(ZoomControl zc, AvaloniaPropertyC
         zc._translateTransform.Y = (double)e.NewValue!;
         if (!zc._isZooming) zc.Mode = ZoomControlModes.Custom;
         zc.OnPropertyChanged(nameof(Presenter));
-        if (!zc._isZooming) zc.Presenter?.InvalidateVisual();
+        zc.InvalidatePresenterTransform(!zc._isZooming);
         zc.ScheduleViewportUpdate();
     }
 
@@ -371,7 +402,7 @@ private static void Zoom_PropertyChanged(ZoomControl zc, AvaloniaPropertyChanged
         }
 
         zc.OnPropertyChanged(nameof(Presenter));
-        zc.Presenter?.InvalidateVisual();
+        zc.InvalidatePresenterTransform();
         zc.OnPropertyChanged(nameof(Zoom));
         zc.HookAfterZoomChanging();
     }