Spatial Filter (XCLIP command) command in C#

By Augusto Goncalves

Is it possible to programmatically create a spatial filter like XCLIP command in .Net? Unfortunately the AcDbIndexFilterManager::addFilter method is not exposed, but we can P/Invoke it. The following C# sample illustrates how to do that. Note that some version specific decorated names are used (see EntryPoint parameter), which can cause this code not to work on other versions.

// required ObjectARX methods, called with P/Invoke    // this is valid for R19 release (AutoCAD 2013)    [DllImport("acdb19.dll",        CharSet = CharSet.Unicode,        CallingConvention = CallingConvention.Cdecl,        EntryPoint = "?addFilter@AcDbIndexFilterManager@@YA?AW4ErrorStatus@Acad@@PAVAcDbBlockReference@@PAVAcDbFilter@@@Z")]    private static extern int addFilter32(IntPtr pBlkRef, IntPtr pFilter);    [DllImport("acdb19.dll",        CharSet = CharSet.Unicode,        CallingConvention = CallingConvention.Cdecl,        EntryPoint = "?addFilter@AcDbIndexFilterManager@@YA?AW4ErrorStatus@Acad@@PEAVAcDbBlockReference@@PEAVAcDbFilter@@@Z")]    private static extern int addFilter64(IntPtr pBlkRef, IntPtr pFilter);         ///     /// Check if the OS is 32 or 64 bit    ///     static public bool is64bits    {      get { return (Application.GetSystemVariable        ("PLATFORM").ToString().IndexOf("64") > 0); }    }         //Create a spatial filter on the selected block reference    //create rectangular cliping area by providing the 2 corners    [CommandMethod("NetClip")]    public void NetClip()    {      // required variables      Document doc = Application.DocumentManager.        MdiActiveDocument;      Database db = doc.Database;      Editor ed = doc.Editor;           // select a block reference      PromptEntityOptions peo = new PromptEntityOptions(        "nSelect a block reference: ");      peo.SetRejectMessage("nMust be a block reference...");      peo.AddAllowedClass(typeof(BlockReference), true);      PromptEntityResult per = ed.GetEntity(peo);      if (per.Status != PromptStatus.OK) return;           PromptPointOptions ppo = new PromptPointOptions(        "nSelect rect clip 1st corner: ");      PromptPointResult ppr1 = ed.GetPoint(ppo);           if (ppr1.Status != PromptStatus.OK)        return;           PromptCornerOptions pco = new PromptCornerOptions(        "nSelect rect clip 2nd corner: ", ppr1.Value);      pco.UseDashedLine = true;           PromptPointResult ppr2 = ed.GetCorner(pco);           if (ppr2.Status != PromptStatus.OK)        retur
n;           using (Transaction trans = db.TransactionManager        .StartTransaction())      {        BlockReference bref = trans.GetObject(per.ObjectId,          OpenMode.ForWrite) as BlockReference;             //Define clip rectangle        Point3d pt3d1 = ppr1.Value.TransformBy(          bref.BlockTransform.Inverse());        Point3d pt3d2 = ppr2.Value.TransformBy(          bref.BlockTransform.Inverse());             Point2dCollection boundary =           GetClipRectangle(pt3d1, pt3d2);             double elevation = 0.0;             SpatialFilter filter = new SpatialFilter();             filter.Definition = new           SpatialFilterDefinition(boundary,          bref.Normal, elevation, 1000, -1000, true);             //P/Invoke AcDbIndexFilterManager::addFilter        int es;        if (is64bits)          es = addFilter64(bref.UnmanagedObject,            filter.UnmanagedObject);        else          es = addFilter32(bref.UnmanagedObject,            filter.UnmanagedObject);             if (es == 0)        {          ed.WriteMessage(            "nSpatial filter
added successfully...");          DrawClipBoundary(boundary, bref,             bref.Normal, elevation);        }        else        {          ed.WriteMessage(            "nSpatial filter failed:(...Error code:"            + es.ToString());        };             // need to explicitely close the filter        filter.Close();        trans.Commit();      }    }         // the clip rectangle needs to be provided     // with (lower-left, upper-right) so we may     // need to re-arrange depending on how the     // user selected corners    Point2dCollection GetClipRectangle(      Point3d p1, Point3d p2)    {      Point2dCollection clipRect =         new Point2dCollection();           double minX = p1.X;      double minY = p1.Y;           double maxX = p2.X;      double maxY = p2.Y;           if (minX > p2.X)      {        minX = p2.X;        maxX = p1.X;      }           if (minY > p2.Y)      {        minY = p2.Y;        maxY = p1.Y;      }           clipRect.Add(new Point2d(minX, minY));      clipRect.Add(new Point2d(maxX, maxY));           return clipRect;    }         //Just an optional method in order to visualize the clip area    void DrawClipBoundary(      Point2dCollection boundary,      BlockReference bref,      Vector3d Normal,      double elevation)    {      Database db = HostApplicationServices.        WorkingDatabase;           using (Transaction trans =         db.TransactionManager.StartTransaction())      {        BlockTable bT = trans.GetObject(          db.BlockTableId, OpenMode.ForRead)           as BlockTable;        BlockTableRecord bTR = trans.GetObject(          bT[BlockTableRecord.ModelSpace],           OpenMode.ForWrite)            as BlockTableRecord;             Polyline pline = new Polyline();        pline.Closed = true;        pline.Thickness = 0.0;        pline.SetPropertiesFrom(bref);        pline.Normal = Normal;        pline.Elevation = elevation;        pline.ColorIndex = 1;             pline.AddVertexAt(0,           new Point2d(            boundary[0].X, boundary[0].Y), 0, 0, 0);        pline.AddVertexAt(1,          new Point2d(            boundary[0].X, boundary[1].Y), 0, 0, 0);        pline.AddVertexAt(2,          new Point2d(            boundary[1].X, boundary[1].Y), 0, 0, 0);        pline.AddVertexAt(3,           new Point2d(            boundary[1].X, boundary[0].Y), 0, 0, 0);             pline.TransformBy(bref.BlockTransform);             bTR.AppendEntity(pline);        trans.AddNewlyCreatedDBObject(pline, true);        trans.Commit();      }    }