ArcObjects – Drawing Custom Selection Box for Selections

arcobjectssymbology

I have some code that I'm using to selecting features in a certain extent. I already rigged the tool properly, so it selected the objects as needed, but I want to draw interactively the selection box the user is making.

I'm using IScreenDisplay.DrawRectangle method, but it pollutes the screen with many small rectangles. Is there a way to clear up the old drawings in the screen?

This Draw method is being called from a mouse move event. Any ideas?

Here are two methods I'm using to do the dirty work:

public override void OnMouseMove(int button, int shift, int x, int y)
{
    if (button != 1)
        return;

    if (!_IsSelectOperation)
        return;

    endPoint = focusScreenDisplay.DisplayTransformation.ToMapPoint(x, y);
    envelope.PutCoords(startPoint.X, startPoint.Y, endPoint.X, endPoint.Y);
    DrawEnvelope(envelope, BuildSelectionSymbol(), focusScreenDisplay);
}

private void DrawEnvelope(IEnvelope envelope, ISymbol symbol, IScreenDisplay screenDisplay)
{
    screenDisplay.StartDrawing(screenDisplay.WindowDC, 0);
    screenDisplay.SetSymbol(symbol);
    screenDisplay.DrawRectangle(envelope);
    screenDisplay.FinishDrawing();
}

Here is the code for BuildSelectionSymbol:

private ISymbol BuildSelectionSymbol()
{
    IColor fillColor = new RgbColorClass();
    fillColor.Transparency = 0;

    IRgbColor outlineColor = new RgbColorClass();
    outlineColor.Red = 0;
    outlineColor.Green = 0;
    outlineColor.Blue = 0;

    ISimpleLineSymbol lineSymbol = new SimpleLineSymbolClass();
    lineSymbol.Color = outlineColor as IColor;
    lineSymbol.Width = 1;
    lineSymbol.Style = esriSimpleLineStyle.esriSLSDash;

    ISimpleFillSymbol fillSymbol = new SimpleFillSymbolClass();
    fillSymbol.Color = fillColor;
    fillSymbol.Outline = lineSymbol;
    fillSymbol.Style = esriSimpleFillStyle.esriSFSHollow;

    ISymbol symbol = fillSymbol as ISymbol;
    symbol.ROP2 = esriRasterOpCode.esriROPNOP;

    return symbol;
}

I already have the answer for this. I was using a normal envelope. The deal is that ESRI already has something to handle that for you and it's contained in INewEnvelopeFeedback class.

http://help.arcgis.com/en/sdk/10.0/arcobjects_net/conceptualhelp/index.html#/Sample_Display_feedback/000100000m9s000000/

Actually, this interface got me where the code snippet in the question was. It stills draws all the rectangles, but I still need a way to clean them.

Any ideas?

Best Answer

It stills draws all the rectangles, but I still need a way to clean them.

For the linesymbol, fillsymbol and symbol, set ROP2 = esriRasterOpCode.esriROPNotXOrPen.

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