fix #203: preserve animation on appearance updates

tests/AcDream.App.Tests/Rendering/LiveAppearanceAnimationTests.cs

@@ -0,0 +1,65 @@
+using System.Numerics;
+using AcDream.App.Rendering;
+using AcDream.Core.Physics;
+using AcDream.Core.World;
+using DatReaderWriter.DBObjs;
+
+namespace AcDream.App.Tests.Rendering;
+
+public sealed class LiveAppearanceAnimationTests
+{
+    [Fact]
+    public void RebindAppearance_PreservesEntitySequencerAndPlaybackState()
+    {
+        var setup = new Setup();
+        var animation = new Animation();
+        var sequencer = new AnimationSequencer(setup, new MotionTable(), new NullLoader());
+        var oldEntity = Entity(0x70000001u, 0x01000001u);
+        var state = new GameWindow.AnimatedEntity
+        {
+            Entity = oldEntity,
+            Setup = setup,
+            Animation = animation,
+            LowFrame = 2,
+            HighFrame = 9,
+            Framerate = 30f,
+            Scale = 1f,
+            PartTemplate = [(0x01000001u, null)],
+            CurrFrame = 6.5f,
+            Sequencer = sequencer,
+        };
+        IReadOnlyList<MeshRef> dressedParts =
+        [
+            new MeshRef(0x01000002u, Matrix4x4.Identity),
+            new MeshRef(0x01000003u, Matrix4x4.CreateTranslation(1f, 2f, 3f)),
+        ];
+
+        oldEntity.ApplyAppearance(dressedParts, paletteOverride: null, partOverrides: []);
+        GameWindow.RebindAnimatedEntityForAppearance(
+            state, oldEntity, setup, 1.25f, dressedParts);
+
+        Assert.Same(oldEntity, state.Entity);
+        Assert.Same(dressedParts, state.Entity.MeshRefs);
+        Assert.Same(sequencer, state.Sequencer);
+        Assert.Equal(6.5f, state.CurrFrame);
+        Assert.Equal((2, 9, 30f), (state.LowFrame, state.HighFrame, state.Framerate));
+        Assert.Equal(1.25f, state.Scale);
+        Assert.Equal(new[] { 0x01000002u, 0x01000003u },
+            state.PartTemplate.Select(part => part.GfxObjId));
+    }
+
+    private static WorldEntity Entity(uint id, uint gfxObjId) => new()
+    {
+        Id = id,
+        ServerGuid = 0x50000001u,
+        SourceGfxObjOrSetupId = 0x02000001u,
+        Position = Vector3.Zero,
+        Rotation = Quaternion.Identity,
+        MeshRefs = [new MeshRef(gfxObjId, Matrix4x4.Identity)],
+    };
+
+    private sealed class NullLoader : IAnimationLoader
+    {
+        public Animation? LoadAnimation(uint id) => null;
+    }
+}