perf(streaming): cursor publication across frame budgets

tests/AcDream.App.Tests/Streaming/LandblockRenderPublisherTests.cs

@@ -1,5 +1,6 @@
 using System.Numerics;
 using System.Reflection;
+using System.Collections.Immutable;
 using AcDream.App.Rendering;
 using AcDream.App.Rendering.Wb;
 using AcDream.App.Streaming;
@@ -194,6 +195,47 @@ public sealed class LandblockRenderPublisherTests
         Assert.Equal(1, first.Diagnostics.CompleteCount);
     }
 
+    [Fact]
+    public void RetainedEnvCellPublisher_AdvancesOneShellBeforeAtomicCommit()
+    {
+        var envPublisher = new RecordingEnvCellPublisher();
+        EnvCellLandblockBuild envCells = new(
+            LandblockId,
+            Array.Empty<LoadedCell>(),
+            [
+                Shell(0xA9B40100u, 1),
+                Shell(0xA9B40101u, 2),
+                Shell(0xA9B40102u, 3),
+            ]);
+        var publisher = new LandblockRenderPublisher(
+            publishTerrain: static (_, _, _) => { },
+            removeTerrain: static _ => { },
+            cellVisibility: new CellVisibility(),
+            worldState: new GpuWorldState(),
+            envCellPublisher: envPublisher);
+        LandblockRenderPublication receipt = publisher.PreparePublication(
+            Build(envCells),
+            EmptyMesh());
+        publisher.BeginPublication(receipt);
+
+        Assert.False(publisher.AdvanceCompleteOne(receipt));
+        Assert.Equal(0, envPublisher.AdvancedShells);
+        Assert.Equal(0, envPublisher.CommitCount);
+        for (int shell = 1; shell <= 3; shell++)
+        {
+            Assert.False(publisher.AdvanceCompleteOne(receipt));
+            Assert.Equal(shell, envPublisher.AdvancedShells);
+            Assert.Equal(0, envPublisher.CommitCount);
+        }
+
+        Assert.False(publisher.AdvanceCompleteOne(receipt));
+        Assert.Equal(0, envPublisher.CommitCount);
+        Assert.False(publisher.AdvanceCompleteOne(receipt));
+        Assert.Equal(1, envPublisher.CommitCount);
+        Assert.True(publisher.AdvanceCompleteOne(receipt));
+        Assert.Equal(1, publisher.Diagnostics.CompleteCount);
+    }
+
     [Fact]
     public void PrepareAndRetirementOperationsStayBalancedAtTheirOwnerBoundary()
     {
@@ -341,6 +383,19 @@ public sealed class LandblockRenderPublisherTests
         InverseWorldTransform = Matrix4x4.Identity,
     };
 
+    private static EnvCellShellPlacement Shell(uint cellId, ulong geometryId) =>
+        new(
+            cellId,
+            geometryId,
+            EnvironmentId: 1u,
+            CellStructure: 0,
+            Surfaces: ImmutableArray<ushort>.Empty,
+            WorldPosition: Vector3.Zero,
+            Rotation: Quaternion.Identity,
+            Transform: Matrix4x4.Identity,
+            LocalBounds: new WbBoundingBox(Vector3.Zero, Vector3.One),
+            WorldBounds: new WbBoundingBox(Vector3.Zero, Vector3.One));
+
     private static LandblockMeshData MeshAtHeights(float first, float second) => new(
         [
             new TerrainVertex(new Vector3(0f, 0f, first), Vector3.UnitZ, 0, 0, 0, 0),
@@ -362,4 +417,42 @@ public sealed class LandblockRenderPublisherTests
         }
         throw new DirectoryNotFoundException("Could not locate repository root.");
     }
+
+    private sealed class RecordingEnvCellPublisher :
+        IEnvCellLandblockPublisher
+    {
+        private readonly object _owner = new();
+
+        public int AdvancedShells { get; private set; }
+        public int CommitCount { get; private set; }
+
+        public EnvCellLandblockPublication PreparePublication(
+            EnvCellLandblockBuild build) =>
+            new(_owner, build);
+
+        public bool AdvancePreparationOne(
+            EnvCellLandblockPublication publication)
+        {
+            Assert.Same(_owner, publication.Owner);
+            if (publication.PreparationCommitted)
+                return true;
+            if (publication.ShellCursor < publication.Build.Shells.Length)
+            {
+                publication.ShellCursor++;
+                AdvancedShells++;
+                return false;
+            }
+
+            publication.PreparationCommitted = true;
+            return true;
+        }
+
+        public void CommitPublication(
+            EnvCellLandblockPublication publication)
+        {
+            Assert.True(publication.PreparationCommitted);
+            publication.PublicationCommitted = true;
+            CommitCount++;
+        }
+    }
 }