Tag: Graphics

In a previous post I showed a quick demo of a PathBuilder class I created to help draw dynamic shapes. I would like to include a simple example of how to create Shape controls using the same tool.

I have created a very simple Triangle control which you can download and see run.

Download Triangle Demo

Here is the actual Triangle class

class Triangle : Shape
{
    private Geometry geometry;

    public static readonly DependencyProperty P1Property = DependencyProperty.Register(
        "P1",
        typeof(Point),
        typeof(Triangle),
        new UIPropertyMetadata(OnPointChanged));

    public static readonly DependencyProperty P2Property = DependencyProperty.Register(
        "P2",
        typeof(Point),
        typeof(Triangle),
        new UIPropertyMetadata(OnPointChanged));

    public static readonly DependencyProperty P3Property = DependencyProperty.Register(
        "P3",
        typeof(Point),
        typeof(Triangle),
        new UIPropertyMetadata(OnPointChanged));

    public Point P1
    {
        get { return (Point)GetValue(P1Property); }
        set { SetValue(P1Property, value); }
    }

    public Point P2
    {
        get { return (Point)GetValue(P2Property); }
        set { SetValue(P2Property, value); }
    }

    public Point P3
    {
        get { return (Point)GetValue(P3Property); }
        set { SetValue(P3Property, value); }
    }

    private static void OnPointChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        ((Triangle)sender).UpdateGeometry();
    }

    private void UpdateGeometry()
    {
        this.geometry = PathBuilder.Start()
            .Move(P1)
            .DrawLine(P2)
            .DrawLine(P3)
            .DrawLine(P1)
            .Close()
            .ToGeometry();
    }

    public Triangle()
    {
        this.UpdateGeometry();
    }
        

    protected override Geometry DefiningGeometry
    {
        get 
        {
            return this.geometry;
        }
    }
}

Notice I inherited from Shape and use the PathBuilder to generate a Geometry object and return it in the protected DefiningGeometry property.

I had to add one method to my PathBuilder:

public static Geometry ToGeometry(this IPath path)
{
    var converter = new GeometryConverter();
    return (Geometry)converter.ConvertFromString(path.Data);
}

This method converts the path string into a Geometry object. Here is the xaml to display this control:

<c:Triangle P1="0,0" P2="0,100" P3="100,100" StrokeThickness="1" Stroke="Black" Fill="Blue" />

And finally the Triangle in action