Avalonia/tests/Avalonia.Controls.UnitTests/PullToRefresh/ScrollViewerIRefreshInfoProviderAdapterTests.cs

using System.Linq;
using System.Reflection;
using Avalonia.Controls.PullToRefresh;
using Avalonia.Controls.Templates;
using Avalonia.Input;
using Avalonia.UnitTests;
using Xunit;

namespace Avalonia.Controls.UnitTests.PullToRefresh
{
    public class ScrollViewerIRefreshInfoProviderAdapterTests : ScopedTestBase
    {
        // Repro for the "gesture recognizer leaked across Adapt() calls" bug.
        //
        // Adapt() cleans up the previous ScrollViewer's pointer handlers and the previous
        // RefreshInfoProvider's pull-event handlers, but never removes the previously-created
        // ScrollablePullGestureRecognizer from _interactionSource.GestureRecognizers.
        // Each subsequent Adapt() instantiates and adds a new recognizer, so the input element
        // ends up holding N recognizers after N calls. They all listen for the same pointer
        // events and raise duplicate PullGesture/PullGestureEnded pairs, which (combined with
        // the _entered desync fix in RefreshInfoProvider) corrupts the visualizer state.
        [Fact]
        public void Adapt_called_twice_does_not_leak_pull_gesture_recognizer()
        {
            var sv = new ScrollViewer
            {
                Template = new FuncControlTemplate<ScrollViewer>(ScrollViewerTests.CreateTemplate),
                Content = new Border(),
            };

            // Wrap in a TestRoot and execute the layout pass so Loaded fires and the
            // visual tree under the ScrollContentPresenter is fully wired up
            // (otherwise the adapter never reaches MakeInteractionSource).
            var root = new TestRoot(sv);
            root.LayoutManager.ExecuteInitialLayoutPass();

            var adapter = new ScrollViewerIRefreshInfoProviderAdapter(PullDirection.TopToBottom, isMouseEnabled: false);

            adapter.Adapt(sv, new Size(100, 100));
            var interactionSource = GetInteractionSource(adapter);
            Assert.NotNull(interactionSource);
            var afterFirst = interactionSource.GestureRecognizers.OfType<ScrollablePullGestureRecognizer>().Count();
            Assert.Equal(1, afterFirst);

            adapter.Adapt(sv, new Size(100, 100));
            var interactionSourceAfter = GetInteractionSource(adapter);
            Assert.NotNull(interactionSourceAfter);
            var afterSecond = interactionSourceAfter.GestureRecognizers.OfType<ScrollablePullGestureRecognizer>().Count();
            Assert.Equal(1, afterSecond);
        }

        private static InputElement GetInteractionSource(ScrollViewerIRefreshInfoProviderAdapter adapter)
        {
            var field = typeof(ScrollViewerIRefreshInfoProviderAdapter)
                .GetField("_interactionSource", BindingFlags.Instance | BindingFlags.NonPublic);
            return (InputElement)field!.GetValue(adapter)!;
        }
    }
}