Merge pull request #5042 from AvaloniaUI/update_geometry_segments_onpropchange

Update Path from PathSegments

src/Avalonia.Visuals/Media/PathFigure.cs

@@ -1,3 +1,7 @@
+#nullable enable
+using System;
+using System.Linq;
+using Avalonia.Collections;
 using Avalonia.Metadata;
 
 namespace Avalonia.Media
@@ -8,22 +12,36 @@ namespace Avalonia.Media
         /// Defines the <see cref="IsClosed"/> property.
         /// </summary>
         public static readonly StyledProperty<bool> IsClosedProperty
-                            = AvaloniaProperty.Register<PathFigure, bool>(nameof(IsClosed), true);
+            = AvaloniaProperty.Register<PathFigure, bool>(nameof(IsClosed), true);
+
         /// <summary>
         /// Defines the <see cref="IsFilled"/> property.
         /// </summary>
         public static readonly StyledProperty<bool> IsFilledProperty
-                            = AvaloniaProperty.Register<PathFigure, bool>(nameof(IsFilled), true);
+            = AvaloniaProperty.Register<PathFigure, bool>(nameof(IsFilled), true);
+
         /// <summary>
         /// Defines the <see cref="Segments"/> property.
         /// </summary>
-        public static readonly DirectProperty<PathFigure, PathSegments> SegmentsProperty
-                        = AvaloniaProperty.RegisterDirect<PathFigure, PathSegments>(nameof(Segments), f => f.Segments, (f, s) => f.Segments = s);
+        public static readonly DirectProperty<PathFigure, PathSegments?> SegmentsProperty
+            = AvaloniaProperty.RegisterDirect<PathFigure, PathSegments?>(
+                nameof(Segments), 
+                f => f.Segments,
+                (f, s) => f.Segments = s);
+
         /// <summary>
         /// Defines the <see cref="StartPoint"/> property.
         /// </summary>
         public static readonly StyledProperty<Point> StartPointProperty
-                        = AvaloniaProperty.Register<PathFigure, Point>(nameof(StartPoint));
+            = AvaloniaProperty.Register<PathFigure, Point>(nameof(StartPoint));
+
+        internal event EventHandler? SegmentsInvalidated;
+
+        private PathSegments? _segments;
+
+        private IDisposable? _segmentsDisposable;
+
+        private IDisposable? _segmentsPropertiesDisposable;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PathFigure"/> class.
@@ -33,6 +51,31 @@ namespace Avalonia.Media
             Segments = new PathSegments();
         }
 
+        static PathFigure()
+        {
+            SegmentsProperty.Changed.AddClassHandler<PathFigure>(
+                (s, e) =>
+                s.OnSegmentsChanged());
+        }
+
+        private void OnSegmentsChanged()
+        {
+            _segmentsDisposable?.Dispose();
+            _segmentsPropertiesDisposable?.Dispose();
+
+            _segmentsDisposable = _segments?.ForEachItem(
+                _ => InvalidateSegments(),
+                _ => InvalidateSegments(),
+                InvalidateSegments);
+
+            _segmentsPropertiesDisposable = _segments?.TrackItemPropertyChanged(_ => InvalidateSegments());
+        }
+
+        private void InvalidateSegments()
+        {
+            SegmentsInvalidated?.Invoke(this, EventArgs.Empty);
+        }
+
         /// <summary>
         /// Gets or sets a value indicating whether this instance is closed.
         /// </summary>
@@ -64,7 +107,7 @@ namespace Avalonia.Media
         /// The segments.
         /// </value>
         [Content]
-        public PathSegments Segments
+        public PathSegments? Segments
         {
             get { return _segments; }
             set { SetAndRaise(SegmentsProperty, ref _segments, value); }
@@ -81,22 +124,23 @@ namespace Avalonia.Media
             get { return GetValue(StartPointProperty); }
             set { SetValue(StartPointProperty, value); }
         }
+        
+        public override string ToString()
+            => $"M {StartPoint} {string.Join(" ", _segments ?? Enumerable.Empty<PathSegment>())}{(IsClosed ? "Z" : "")}";
 
         internal void ApplyTo(StreamGeometryContext ctx)
         {
             ctx.BeginFigure(StartPoint, IsFilled);
 
-            foreach (var segment in Segments)
+            if (Segments != null)
             {
-                segment.ApplyTo(ctx);
+                foreach (var segment in Segments)
+                {
+                    segment.ApplyTo(ctx);
+                }
             }
 
             ctx.EndFigure(IsClosed);
         }
-
-        private PathSegments _segments;
-
-        public override string ToString()
-            => $"M {StartPoint} {string.Join(" ", _segments)}{(IsClosed ? "Z" : "")}";
     }
-}
+}

src/Avalonia.Visuals/Media/PathGeometry.cs

@@ -104,12 +104,26 @@ namespace Avalonia.Media
             _figuresPropertiesObserver?.Dispose();
 
             _figuresObserver = figures?.ForEachItem(
-                _ => InvalidateGeometry(),
-                _ => InvalidateGeometry(),
-                () => InvalidateGeometry());
+                s =>
+                {
+                    s.SegmentsInvalidated += InvalidateGeometryFromSegments;
+                    InvalidateGeometry();
+                },
+                s =>
+                {
+                    s.SegmentsInvalidated -= InvalidateGeometryFromSegments;
+                    InvalidateGeometry();
+                },
+                InvalidateGeometry);
+            
             _figuresPropertiesObserver = figures?.TrackItemPropertyChanged(_ => InvalidateGeometry());
+ 
         }
 
+        private void InvalidateGeometryFromSegments(object _, EventArgs __)
+        {
+            InvalidateGeometry();
+        }
 
         public override string ToString()
             => $"{(FillRule != FillRule.EvenOdd ? "F1 " : "")}{(string.Join(" ", Figures))}";

tests/Avalonia.Visuals.UnitTests/Media/PathSegmentTests.cs

@@ -0,0 +1,34 @@
+using Avalonia.Media;
+using Xunit;
+
+namespace Avalonia.Visuals.UnitTests.Media
+{
+    public class PathSegmentTests
+    {
+        [Fact]
+        public void PathSegment_Triggers_Invalidation_On_Property_Change()
+        {
+            var targetSegment = new ArcSegment()
+            {
+                Size = new Size(10, 10),
+                Point = new Point(5, 5)
+            };
+
+            var target = new PathGeometry
+            {
+                Figures = new PathFigures
+                {
+                    new PathFigure { IsClosed = false, Segments = new PathSegments { targetSegment } }
+                }
+            };
+            
+            var changed = false;
+
+            target.Changed += (s, e) => changed = true;
+
+            targetSegment.Size = new Size(20, 20);
+
+            Assert.True(changed);
+        }
+    }
+}