Topic: Double Drag behavior

[mohnston]

I've been using this jig class but have noticed a problem.

When I'm dragging the ent I get two ghost copies. One on my cursor and one at double the distance and direction from the start point of the drag to the current cursor point.
When I drop the ent it is fine. Only the ent on my cursor is placed on the drawing and it is where I picked. The double ghost thing is bugging me. Probably a logic problem but I don't see it.

I've tried to keep the class as simple as possible.
What might be causing this behavior?

Code: [Select]

public class JigEnt : DrawJig
    {
        #region private member fields

        private Point3d previousCursorPosition;

        private Point3d currentCursorPosition;

        private Entity entityToDrag;

        #endregion

        Autodesk.AutoCAD.ApplicationServices.Document doc =
            acadApp.DocumentManager.MdiActiveDocument;

        public void DragEnt(
            ObjectId EntObjectID,
            Point3d StartPoint)
        {
            try
            {
                using (Transaction trans = doc.TransactionManager.StartTransaction())
                {
                    // Assign the Entity based on the ObjectID provided
                    entityToDrag = (Entity)trans.GetObject(EntObjectID, OpenMode.ForWrite);
                    //Initialize cursor position
                    previousCursorPosition = StartPoint;
                    doc.Editor.Drag(this);
                    trans.Commit();
                }               
            }
            catch (System.Exception)
            {
               
            }

        }

        protected override SamplerStatus Sampler(JigPrompts prompts)
        {
            //Get the current cursor position
            PromptPointResult userFeedback = prompts.AcquirePoint();
            currentCursorPosition = userFeedback.Value;

            if (CursorHasMoved())
            {
                //Get the vector of the move
                Vector3d displacementVector = previousCursorPosition.GetVectorTo(currentCursorPosition);
               
                //Transform the ent to the new location
                entityToDrag.TransformBy(Matrix3d.Displacement(displacementVector));
               
                //Save the cursor position
                previousCursorPosition = currentCursorPosition;

                return SamplerStatus.OK;
            }
            else
            {
                return SamplerStatus.NoChange;
            }
        }

        protected override bool WorldDraw(WorldDraw draw)
        {
            draw.Geometry.Draw(entityToDrag);
            return true;
        }

        private bool CursorHasMoved()
        {
            return !(currentCursorPosition == previousCursorPosition);
        }

    }


[Glenn R]

At first scan, your CursorHasMoved function looks...wrong.

It should probably be:

Code: [Select]

return (currentCursorPosition != previousCursorPosition);


[mohnston]

I'm not sure if
(WrongnessOf(return !(currentCursorPosition == previousCursorPosition)
>
WrongnessOf(return (currentCursorPosition != previousCursorPosition)))

but making that change didn't change the behavior.

My mistake is probably much much dumber than that.

[Glenn R]

Like I said - scan ie quick.

I still think that judging by your method name, it should be as I suggested. I'll have to dig up some of my jig code to do a deeper analysis, but I'm tired and might do that tomorrow.

For others that may want to help, you haven't mentioned the following:

AutoCAD version
.NET Framework version
.NET Framework version being targeted (if applicable)
Visual Studio version

[mohnston]

I do appreciate your scan.

AutoCAD 2008
.NET framework 2.0 (using and targeted)
VS 2008 (framework 2.0 selected)

[It's Alive!]

I’m using pretty much the same routine as you ( except my entity-to-drag is not database resident )
without any issues, you might try using a clone of your entity, then use the final coordinates of the jig to transform your original entity. 
If that makes sense .

[Glenn R]

CloneMeForDragging or some such if memory serves....