A customer wanted to get the closest point on a drawing curve when the user clicks a location on the sheet. The workflow is simple: start mouse event, watch MouseEvent.OnMouseClick. In the event, calculate the closest point on the curve.

However, it looks API only provides GetClosestPoint method for Edge and Face. So we would need to calculate the closest point ourselves. There are many discussions on the algorism how to get a nearest point of 2D curve, I tested with the simplest one: disperse the parameters of a curve, then get the point, calculate the distance with the mouse point, find the shortest one.

The below is the code of MouseEvent. The whole code project is attached. It is a standalone EXE. It assumes a drawing curve is selected, then click [start event], mouse click a location, the closest point will be displayed as a client graphics point. Click [stop event] to terminate the custom mouse event.

you can change to other more efficient algorism of getting close point.

Private Sub oME_OnMouseClick(Button As MouseButtonEnum, ShiftKeys As ShiftStateEnum, ModelPosition As Point, ViewPosition As Point2d, View As View) Handles oME.OnMouseClick Dim oPickPtX = ModelPosition.X Dim oPickPtY = ModelPosition.Y Dim oCurve As DrawingCurve oCurve = oOneDrawingCurve.Parent Dim oEvaluator As Curve2dEvaluator oEvaluator = oCurve.Evaluator2D Dim oMinP, oMaxP oEvaluator.GetParamExtents(oMinP, oMaxP) Dim oMinDis = 100000000000.0 ' Get the curve length Dim dLen As Double Call oEvaluator.GetLengthAtParam(oMinP, oMaxP, dLen) Dim dInc As Double dInc = dLen / 100 'consider 100 points Dim dLenInc As Double dLenInc = 0 Dim dparams(0) As Double dparams(0) = oMinP Dim iCnt As Integer Dim oClosestPtX As Double = 0 Dim oClosestPtY As Double = 0 For iCnt = 0 To 100 Dim dParam As Double Call oEvaluator.GetParamAtLength(oMinP, dInc * iCnt, dParam) ' a spline in planar sketch is 2d. its points are ' 2d (x,y) Dim dPts(1) As Double dparams(0) = dParam Call oEvaluator.GetPointAtParam(dparams, dPts) Dim oEachDis = Math.Sqrt(Math.Pow((dPts(0) - oPickPtX), 2) +

Math.Pow((dPts(1) - oPickPtY), 2)) 'smaller distance? If (oEachDis < oMinDis) Then oMinDis = oEachDis oClosestPtX = dPts(0) oClosestPtY = dPts(1) End If Next 'draw the point graphics Dim oCoordSet As Object = Nothing Dim oGraphicsNode As Object = Nothing Dim oDataSets As Object = Nothing 'get datasets, dataset, graphics node getCG(oGraphicsNode, oCoordSet, oDataSets) 'prepare the coordinates Dim oPointCoords(2) As Double oPointCoords(0) = oClosestPtX : oPointCoords(1) = oClosestPtY : oPointCoords(2) = 0 'oPointCoords(0) = dPts(0) : oPointCoords(1) = dPts(1) : oPointCoords(2) = 0 Call oCoordSet.PutCoordinates(oPointCoords) 'add PointGraphics Dim oPointGraphics As PointGraphics oPointGraphics = oGraphicsNode.AddPointGraphics 'set the related oPointGraphics.PointRenderStyle = PointRenderStyleEnum.kCrossPointStyle oPointGraphics.CoordinateSet = oCoordSet oPointGraphics.BurnThrough = True invApp.ActiveView.Update() End Sub