布局和视口

布局和视口是CAD出图的重要手段之一，其中视口可以映射到模型空间的任一范围，进而在布局空间灵活组织图形成果。
本文针对布局创建及切换、视口创建封装若干接口。

切换布局

借助Database的TileMode属性来切换到模型空间

public static void SwitchLayout(this Document doc, string layoutName)
{
    if (string.IsNullOrWhiteSpace(layoutName) || ObjectId.Null == doc.Database.GetLayoutIdByName(layoutName)) 
        return;
    using (var docLock = doc.LockDocument())
        LayoutManager.Current.CurrentLayout = layoutName;
}

public static void SwitchToModel()
{
    var doc = DwgOperators.ThisDocument;
    using (var docLock = doc.LockDocument())
        doc.Database.TileMode = true;
}

//----------------------------------------------------------------------
private static ObjectId GetLayoutIdByName(this Database db, string layoutName)
{
    ObjectId resId = ObjectId.Null;

    if (string.IsNullOrWhiteSpace(layoutName))
        return resId;

    using (Transaction transaction = db.TransactionManager.StartTransaction())
    {
        BlockTable blockTable = transaction.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;
        foreach (ObjectId id in blockTable)
        {
            BlockTableRecord btr = transaction.GetObject(id, OpenMode.ForRead) as BlockTableRecord;
            if (btr.IsLayout)
            {
                Layout layout = transaction.GetObject(btr.LayoutId, OpenMode.ForRead) as Layout;
                if (layout.LayoutName == layoutName)
                {
                    resId = id;
                    break;
                }
            }
        }
        transaction.Commit();
    }
    return resId;
}

创建布局

为了使新布局生效，调用SwitchLayout()切换一下。

public static ObjectId CreateLayout(this Document doc, string layoutName)
{
    ObjectId resId = ObjectId.Null;
    if (doc == null || string.IsNullOrWhiteSpace(layoutName))
        return resId;
    var db = doc.Database;
    if (db.GetLayoutIdByName(layoutName) != ObjectId.Null) 
        return resId;
    using (var docLock = doc.LockDocument())
    {
        using (Transaction transaction = doc.TransactionManager.StartTransaction())
        {
            DBDictionary layouts = transaction.GetObject(db.LayoutDictionaryId, OpenMode.ForWrite) as DBDictionary;
            resId = LayoutManager.Current.CreateLayout(layoutName);
            transaction.Commit();
        }
    }
    doc.Database.SwitchLayout(layoutName);
    return resId;
}

创建视口

创建从任一矩形创建视口的函数，此函数的开发着实花费了不少精力，感叹一下！

• CreateViewportIntoPaperspace()：创建模型空间中任一矩形的视口（很实用）
• SetViewportLockedLayers()：设置某一视口中的图层状态
• AddUCS()：添加用户坐标系

public static ObjectId CreateViewportIntoPaperspace(this Database db,string layoutName, Point3d leftBottomPoint, double width, double height,double rotation, Point3d viewportLeftBottomPoint, double? viewportWidth = null,double? viewportHeight = null, double scale = 1.0)
{
    ObjectId resId = ObjectId.Null;

    if (string.IsNullOrWhiteSpace(layoutName))
        return resId;

    using (Transaction transaction = db.TransactionManager.StartTransaction())
    {
        Viewport vport = new Viewport();
        
        double vWidth, vHeight;
        if (viewportWidth == null)
            vWidth = width;
        else
            vWidth = viewportWidth.Value;
        if (viewportHeight == null)
            vHeight = height;
        else
            vHeight = viewportHeight.Value;
        vport.CenterPoint = new Point3d(viewportLeftBottomPoint.X + 0.5 * vWidth, viewportLeftBottomPoint.Y + 0.5 * vHeight, 0);
        vport.Width = vWidth;
        vport.Height = vHeight;
        
        var point = CoorTransform(leftBottomPoint, rotation, new Point3d(0.5 * width, 0.5 * height, 0));
        vport.ViewTarget = point;
        
        var ucsId = db.AddUCS($"ucs-{Guid.NewGuid().ToString()}", leftBottomPoint,
                              new Vector3d(Math.Cos(rotation), Math.Sin(rotation), 0),
                              new Vector3d(Math.Cos(rotation + 0.5 * Math.PI), Math.Sin(rotation + 0.5 * Math.PI), 0));
        vport.SetUcs(ucsId);
        
        vport.TwistAngle = Math.PI * 2 - rotation;
        vport.ViewDirection = new Vector3d(0, 0, 1);
        vport.CustomScale = scale;
        resId = db.AddEntity(vport, layoutName);
        db.SwitchLayout(layoutName);
        vport.On = true;

        transaction.Commit();
    }
    return resId;
}

public static void SetViewportLockedLayers(this Document doc, ObjectId id, List<string> frozenLayerNames)
{
    if (doc == null || id == ObjectId.Null) return;
    if (frozenLayerNames == null || frozenLayerNames.Count == 0) return;
    var db = doc.Database;
    using (Transaction transaction = db.TransactionManager.StartTransaction())
    {
        Viewport vp = transaction.GetObject(id, OpenMode.ForWrite) as Viewport;
        if (vp != null)
        {
            LayerTable lt = transaction.GetObject(db.LayerTableId, OpenMode.ForRead) as LayerTable;
            List<ObjectId> layerIds = new List<ObjectId>();
            foreach (var name in frozenLayerNames)
                if (lt.Has(name))
                    layerIds.Add(lt[name]);
            vp.FreezeLayersInViewport(layerIds.GetEnumerator());
        }
        transaction.Commit();
    }
}

//----------------------------------------------------------------------
private static ObjectId AddUCS(this Database db, string ucsName, Point3d origin, Vector3d xAxis, Vector3d yAxis)
{
    ObjectId resId = ObjectId.Null;

    if (string.IsNullOrWhiteSpace(ucsName))
        return resId;

    using (Transaction transaction = db.TransactionManager.StartTransaction())
    {
        UcsTable ucsTable = transaction.GetObject(db.UcsTableId, OpenMode.ForWrite) as UcsTable;
        if (!ucsTable.Has(ucsName))
        {
            UcsTableRecord ucsTableRecord = new UcsTableRecord();
            ucsTableRecord.Name = ucsName;
            ucsTableRecord.Origin = origin;
            ucsTableRecord.XAxis = xAxis;
            ucsTableRecord.YAxis = yAxis;

            resId = ucsTable.Add(ucsTableRecord);
            transaction.AddNewlyCreatedDBObject(ucsTableRecord, true);
            ucsTable.DowngradeOpen();
        }
        else
            resId = ucsTable[ucsName];
        transaction.Commit();
    }
    return resId;
}

private static Point3d CoorTransform(Point3d deltaDist, double rotation, Point3d p1)
{
    double dist1 = Math.Sqrt(p1.X * p1.X + p1.Y * p1.Y);
    double rotation1 = Arctan(p1.Y, p1.X);
    double totalRotation = rotation1 + rotation;
    Point3d resPoint = new Point3d(deltaDist.X + dist1 * Math.Cos(totalRotation), deltaDist.Y + dist1 * Math.Sin(totalRotation), 0);
    return resPoint;
}