--- name: acad-layers description: Layer table, layer records, properties, states, filters, color/linetype assignment --- # AutoCAD Layers Use this skill when creating, reading, or modifying layers — accessing the layer table, setting layer properties (color, linetype, frozen, locked, off), managing layer states, and filtering layers. ## Layer Table Access ```csharp Database db = doc.Database; using (Transaction tr = db.TransactionManager.StartTransaction()) { LayerTable lt = (LayerTable)tr.GetObject(db.LayerTableId, OpenMode.ForRead); // Check if a layer exists (case-insensitive) bool exists = lt.Has("MyLayer"); // Get layer by name ObjectId layerId = lt["MyLayer"]; LayerTableRecord layer = (LayerTableRecord)tr.GetObject(layerId, OpenMode.ForRead); // Get current layer LayerTableRecord current = (LayerTableRecord)tr.GetObject(db.Clayer, OpenMode.ForRead); tr.Commit(); } ``` ### Enumerating All Layers ```csharp LayerTable lt = (LayerTable)tr.GetObject(db.LayerTableId, OpenMode.ForRead); List names = new List(); foreach (ObjectId id in lt) { LayerTableRecord layer = (LayerTableRecord)tr.GetObject(id, OpenMode.ForRead); if (layer.IsDependent) continue; // skip xref layers if (layer.IsLocked) continue; // skip locked layers names.Add(layer.Name); } names.Sort(StringComparer.OrdinalIgnoreCase); ``` ## Creating Layers ### Basic Layer Creation ```csharp private static void EnsureLayerExists(LayerTable lt, Transaction tr, string layerName) { if (string.IsNullOrWhiteSpace(layerName) || layerName == "0") return; if (!lt.Has(layerName)) { lt.UpgradeOpen(); // must upgrade the TABLE, not the record LayerTableRecord newLayer = new LayerTableRecord { Name = layerName }; lt.Add(newLayer); tr.AddNewlyCreatedDBObject(newLayer, true); } } ``` ### Layer with Full Properties ```csharp lt.UpgradeOpen(); LayerTableRecord layer = new LayerTableRecord { Name = "C-ROAD-CURB", Color = Color.FromColorIndex(ColorMethod.ByAci, 3), // green LinetypeObjectId = GetLinetypeId(tr, db, "CONTINUOUS"), LineWeight = LineWeight.LineWeight030, IsPlottable = true, Description = "Road curb lines" }; lt.Add(layer); tr.AddNewlyCreatedDBObject(layer, true); ``` ### Looking Up a Linetype ```csharp private static ObjectId GetLinetypeId(Transaction tr, Database db, string name) { LinetypeTable ltt = (LinetypeTable)tr.GetObject(db.LinetypeTableId, OpenMode.ForRead); if (ltt.Has(name)) return ltt[name]; return db.ContinuousLinetype; // fallback } ``` ## Color Assignment ### ACI (AutoCAD Color Index) ```csharp // Standard ACI color (1-255) layer.Color = Color.FromColorIndex(ColorMethod.ByAci, 1); // red // ByLayer (index 256) and ByBlock (index 0) entity.ColorIndex = 256; // ByLayer entity.ColorIndex = 0; // ByBlock ``` ### True Color (RGB) ```csharp layer.Color = Color.FromRgb(128, 64, 0); // Read back byte r = layer.Color.Red; byte g = layer.Color.Green; byte b = layer.Color.Blue; ``` ### Color Book ```csharp layer.Color = Color.FromNames("PANTONE+ Solid Coated", "PANTONE 185 C"); ``` ## LineWeight Values Common `LineWeight` enum values: - `LineWeight.ByLayer` (-1), `LineWeight.ByBlock` (-2), `LineWeight.ByLineWeightDefault` (-3) - `LineWeight.LineWeight000` (0.00mm), `LineWeight.LineWeight013` (0.13mm) - `LineWeight.LineWeight025` (0.25mm), `LineWeight.LineWeight030` (0.30mm) - `LineWeight.LineWeight050` (0.50mm), `LineWeight.LineWeight100` (1.00mm) ## Transparency ```csharp // Set transparency (0 = opaque, 90 = maximum transparency) // AutoCAD limits transparency to 0–90, not 0–100 layer.Transparency = new Transparency(50); // 50% transparent // Read back int percent = (int)(layer.Transparency.Alpha / 255.0 * 100.0); ``` ## Reading Layer Properties ```csharp private static bool IsLayerUsable(string layerName, Transaction tr, Database db, out string message) { message = string.Empty; LayerTable lt = (LayerTable)tr.GetObject(db.LayerTableId, OpenMode.ForRead); if (!lt.Has(layerName)) { message = $"Layer '{layerName}' was not found."; return false; } LayerTableRecord layer = (LayerTableRecord)tr.GetObject(lt[layerName], OpenMode.ForRead); if (layer.IsDependent) { message = $"Layer '{layerName}' is xref-dependent."; return false; } if (layer.IsLocked) { message = $"Layer '{layerName}' is locked."; return false; } return true; } ``` ## Modifying Layer Properties ```csharp LayerTableRecord layer = (LayerTableRecord)tr.GetObject(lt[layerName], OpenMode.ForRead); layer.UpgradeOpen(); // switch to ForWrite layer.IsLocked = false; layer.IsFrozen = false; layer.IsOff = false; layer.Color = Color.FromColorIndex(ColorMethod.ByAci, 7); ``` ### Setting the Current Layer ```csharp // Set by ObjectId db.Clayer = lt["MyLayer"]; // Verify string currentName = ((LayerTableRecord)tr.GetObject(db.Clayer, OpenMode.ForRead)).Name; ``` ## Deleting and Purging Layers ```csharp // Erase a layer (fails if layer has entities or is current/0/xref) LayerTableRecord layer = (LayerTableRecord)tr.GetObject(lt[layerName], OpenMode.ForWrite); layer.Erase(true); // Check purgeable layers ObjectIdCollection layerIds = new ObjectIdCollection(); foreach (ObjectId id in lt) layerIds.Add(id); db.Purge(layerIds); // removes non-purgeable IDs from the collection foreach (ObjectId id in layerIds) { LayerTableRecord purgeableLayer = (LayerTableRecord)tr.GetObject(id, OpenMode.ForWrite); purgeableLayer.Erase(true); } ``` ## Layer Filters ```csharp // Access the layer filter tree LayerFilterTree filterTree = db.LayerFilters; LayerFilterCollection filters = filterTree.Root.NestedFilters; foreach (LayerFilter filter in filters) { ed.WriteMessage($"\nFilter: {filter.Name}, Expression: {filter.FilterExpression}"); } // Create a new filter LayerFilter newFilter = new LayerFilter(); newFilter.Name = "Road Layers"; newFilter.FilterExpression = "NAME==\"C-ROAD-*\""; filterTree.Root.NestedFilters.Add(newFilter); db.LayerFilters = filterTree; // save back ``` ## Layer States ```csharp LayerStateManager lsm = db.LayerStateManager; // Save current layer states lsm.SaveLayerState("DesignFreeze", LayerStateMasks.Color | LayerStateMasks.On | LayerStateMasks.Frozen); // Restore lsm.RestoreLayerState("DesignFreeze", ObjectId.Null, 0, // no viewport LayerStateMasks.Color | LayerStateMasks.On | LayerStateMasks.Frozen); // Check existence bool exists = lsm.HasLayerState("DesignFreeze"); // Delete lsm.DeleteLayerState("DesignFreeze"); // Export/import .las files lsm.ExportLayerState("DesignFreeze", @"C:\Temp\DesignFreeze.las"); lsm.ImportLayerState(@"C:\Temp\DesignFreeze.las"); ``` ### LayerStateMasks Flags - `LayerStateMasks.On`, `Frozen`, `Locked`, `Color`, `Linetype`, `LineWeight` - `LayerStateMasks.PlotStyle`, `Plot`, `NewViewport`, `Transparency` - Combine with `|` operator ## Gotchas - Layer `"0"` cannot be deleted, renamed, or frozen — it is always present - Must call `UpgradeOpen()` on the **LayerTable** before `Add()`, not on individual records - `IsDependent = true` means xref-dependent layer — cannot modify properties - Setting `IsFrozen = true` on the current layer throws an exception - `Color.FromColorIndex` uses `ColorMethod.ByAci`; ByLayer = index 256, ByBlock = index 0 - `LayerTable.Has()` is case-insensitive - `db.Clayer` requires an ObjectId, not a name string — use `lt["name"]` to convert - Layer names cannot contain: `< > / \ " : ; ? * | = '` - Transparency range is 0–90 (AutoCAD limitation), not 0–100 - Viewport-specific overrides (VP Freeze, VP Color) require the viewport override API, not direct layer properties - Erasing a layer that has entities on it throws — move or erase the entities first ## Related Skills - `acad-blocks` — entities within blocks inherit layer properties - `acad-polylines` — polylines and other entities reference layers via the Layer property - `acad-editor-input` — selection filters can filter entities by DxfCode.LayerName (8)