How to implement extension OSNAP for an entity

By Gopinath Taget

You can define a custom osnap like this:

//-------------------------------------------------------------------    // Osnap classes         class MkrInfo : public AcDbCustomOsnapInfo    {    public:        ACRX_DECLARE_MEMBERS(MkrInfo);             Acad::ErrorStatus   getOsnapInfo(         AcDbEntity*           pickedObject,         Adesk::GsMarker       gsSelectionMark,         const AcGePoint3d&    pickPoint,         const AcGePoint3d&    lastPoint,         const AcGeMatrix3d&   viewXform,         AcArray& snapPoints,         AcDbIntArray &     geomIdsForPts,         AcArray& snapCurves,         AcDbIntArray &     geomIdsForLines);    };                   ACRX_CONS_DEFINE_MEMBERS(MkrInfo, AcDbCustomOsnapInfo, 1);              Acad::ErrorStatus    MkrInfo::getOsnapInfo(     AcDbEntity*           pickedObject,     Adesk::GsMarker       gsSelectionMark,     const AcGePoint3d&    pickPoint,     const AcGePoint3d&    lastPoint,     const AcGeMatrix3d&   viewXform,     AcArray& snapPoints,     AcDbIntArray &     geomIdsFo
rPts,     AcArray& snapCurves,     AcDbIntArray &     geomIdsForLines     )    {        AsDkCurve *p = AsDkCurve::cast(pickedObject);        if (NULL != p)        {            AcGeLineSeg3d *pls1 = new AcGeLineSeg3d;      AcGePoint3d startP, endP;      p->startPoint(startP);      p->m_endPoint(endP);            pls1->set(startP, (endP - startP));            snapCurves.append(pls1);                 AcGeLineSeg3d *pls2 = new AcGeLineSeg3d;            pls2->set(endP, (endP - startP));            snapCurves.append(pls2);        }        return Acad::eOk;    }              //static     MkrInfo _mkrInfo;              class MkrMode : public AcDbCustomOsnapMode    {    public:        const TCHAR* localModeString() const;        const TCHAR* globalModeString() const;        const AcRxClass* entityOsnapClass() const;        AcGiGlyph* gly
ph() const;        const TCHAR*               tooltipString() const;    };         const TCHAR*    MkrMode::localModeString() const    {        return _T("XTNd");    }         const TCHAR*    MkrMode::globalModeString() const    {        return _T("_XTNd");    }         const AcRxClass*    MkrMode::entityOsnapClass() const    {        return MkrInfo::desc();    }         class MyGlyph : public AcGiGlyph    {    public:        Acad::ErrorStatus setLocation(const AcGePoint3d& dcsPoint);        void subViewportDraw(AcGiViewportDraw* vportDrawContext);    private:        AcGePoint3d m_point;    };         Acad::ErrorStatus    MyGlyph::setLocation(const AcGePoint3d& dcsPoint)    {        m_point = dcsPoint;        return Acad::eOk;    }              void    MyGlyph::subViewportDraw(AcGiViewportDraw* p)    {        // not needed for ext-like snaps    }         AcGiGlyph*    MkrMode::glyph() const    {        static MyGlyph mg;        return &mg;    }         const TCHAR*    MkrMode::tooltipString() const    {        return _T("Custom Extend");    }         MkrMode _mkrMode;

And you can register a custom osnap to associate with with an entity as follows:

And unregister as follows: