Field close: drop coverage and tram lines from the map

Shared/AgOpenWeb.RemoteServer/MapBroadcaster.cs

@@ -311,6 +311,17 @@ await _ws.BroadcastAsync(WireCodec.EncodeTick(_projector.BuildTick(_sceneVersion
                             await _ws.BroadcastAsync(WireCodec.EncodeCoverageCells(delta), ct).ConfigureAwait(false);
                         }
                     }
+                    else if (_coverageInitSent && !_snapshotInFlight)
+                    {
+                        // The grid is gone (field closed → ClearFieldBounds). Nothing above runs
+                        // without a grid, so say so explicitly or the clients keep drawing the
+                        // closed field's coverage and perimeter until the next field's init.
+                        _coverageInitSent = false;
+                        _coverageReload = false;
+                        _lastCellSize = 0;
+                        _coverageProjector.ResetSent();
+                        await _ws.BroadcastAsync(WireCodec.EncodeCoverageClear(), ct).ConfigureAwait(false);
+                    }
                 }
                 catch { /* tolerate transient coverage-layer races */ }
 

Shared/AgOpenWeb.RemoteServer/WireCodec.cs

@@ -803,6 +803,11 @@ public static byte[] EncodeCoverageInit(CoverageInitDto c, bool reset)
         return ms.ToArray();
     }
 
+    /// <summary>No coverage grid any more (field closed): a reset init with an empty grid.
+    /// The client drops its raster and perimeter (transport.js / app.js onCoverageInit).</summary>
+    public static byte[] EncodeCoverageClear() =>
+        EncodeCoverageInit(new CoverageInitDto(0, 0, 0, 0, 0), reset: true);
+
     public static byte[] EncodeCoverageCells(CoverageCellsDto c)
     {
         var cells = c.Cells;

Shared/AgOpenWeb.RemoteServer/wwwroot/app.js

@@ -376,6 +376,16 @@ const transport = RemoteTransport.create({
   },
   onCoverageInit(init) {
     const cs = init.cellSize;
+    // An empty reset grid means the field closed: drop the raster and the perimeter.
+    if (init.reset && (init.width <= 0 || init.height <= 0)) {
+      if (cov) {
+        if (cov.skImg) cov.skImg.delete();
+        if (cov.surface) cov.surface.delete();
+        if (cov.covPaint) cov.covPaint.delete();
+      }
+      cov = null; covCells = 0; coverageEdges = null;
+      return;
+    }
     // Grid GROWTH at the same cell size (host bounds-expansion, reset=false): the added ground is
     // empty, so the host resends nothing. Keep the coverage we already have, re-anchor it into the
     // larger grid, and carry on with incremental deltas — no rescan, no repaint, no flicker. A

Shared/AgOpenWeb.ViewModels/MainViewModel.cs

@@ -2084,6 +2084,12 @@ private void ClearFieldState()
         // Clear U-turn state
         ClearYouTurnState();
 
+        // Clear tram lines and the field's tram systems (saved above). Field open clears them
+        // too, but between close and the next open the map was still drawing the old lines.
+        _tramLineService.Clear();
+        _tramSystemLineRanges.Clear();
+        ConfigStore.Tram.Systems.Clear();
+
         // Clear flags (without saving — IsFieldOpen is already false) so they don't carry
         // over into the next field (#107)
         LoadFlagsFromField(null);

Tests/AgOpenWeb.ViewModels.Tests/FlagPersistenceTests.cs

@@ -71,4 +71,23 @@ public async Task ClosingTheField_ClearsTheBackgroundImage()
 
         Assert.That(vm.State.Field.Imagery, Is.Null, "the web client keeps drawing the picture while the scene carries it");
     }
+
+    [Test]
+    public async Task ClosingTheField_ClearsCoverageAndTramLines()
+    {
+        var builder = new MainViewModelBuilder();
+        builder.FieldService.ActiveField.Returns(new Field { Name = "F", DirectoryPath = _dir });
+        var vm = builder.Build();
+        vm.IsFieldOpen = true;
+        var tram = AgOpenWeb.Models.Configuration.ConfigurationStore.Instance.Tram;
+        tram.Systems.Clear();
+        tram.Systems.Add(new AgOpenWeb.Models.Tram.TramSystem { Name = "T" });
+
+        await vm.CloseFieldAsync();
+
+        builder.CoverageMapService.Received().ClearAll();
+        builder.CoverageMapService.Received().ClearFieldBounds();
+        builder.TramLineService.Received().Clear();
+        Assert.That(tram.Systems, Is.Empty, "tram systems are field-scoped; they were saved before the clear");
+    }
 }

Tests/AgOpenWeb.ViewModels.Tests/MainViewModelBuilder.cs

@@ -34,6 +34,7 @@ public class MainViewModelBuilder
     public IModuleCommunicationService ModuleCommunicationService { get; set; } = Substitute.For<IModuleCommunicationService>();
     public IConfigurationService ConfigurationService { get; set; } = Substitute.For<IConfigurationService>();
     public IFieldService FieldService { get; } = Substitute.For<IFieldService>();
+    public AgOpenWeb.Services.Interfaces.ITramLineService TramLineService { get; } = Substitute.For<AgOpenWeb.Services.Interfaces.ITramLineService>();
     public AgOpenWeb.Services.Pipeline.PipelineIntents Intents { get; } = new();
 
     public MainViewModelBuilder()
@@ -87,7 +88,7 @@ public MainViewModel Build()
             audioService: Substitute.For<IAudioService>(),
             elevationLogService: Substitute.For<IElevationLogService>(),
             jobService: Substitute.For<IJobService>(),
-            tramLineService: Substitute.For<AgOpenWeb.Services.Interfaces.ITramLineService>(),
+            tramLineService: TramLineService,
             gpsPipelineService: GpsPipelineService,
             intents: Intents,
             logger: NullLogger<MainViewModel>.Instance,