Custom Widgets

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Nevron Open Vision makes it easy to create custom widgets when you want to extend the functionality of any of the existing widgets. To do that, create a class that inherits from the widget you want to extend and override the methods you want to change. For example, to paint some custom objects on a widget, you can override the OnPrePaint method of the widget.

The following code demonstrates how to create a custom label widget that inherits from NLabel and paints an ellipse occupying 1/3rd of the label bounds (content edge):

Create a custom label widget	Copy Code
public class CustomLabel : NLabel { #region Constructors /// <summary> /// Default constructor. /// </summary> public CustomLabel() { } /// <summary> /// Initializing constructor. /// </summary> /// <param name="text"></param> public CustomLabel(string text) { } /// <summary> /// Static constructor. /// </summary> static CustomLabel() { CustomLabelSchema = NSchema.Create(typeof(CustomLabel), NLabelSchema); } #endregion #region Protected Overrides - Paint protected override void OnPrePaint(NPaintVisitor visitor) { // Paint an ellipse that occupies 1/3rd of the label bounds NRectangle bounds = GetContentEdge(); visitor.SetFill(new NHatchFill(ENHatchStyle.Sphere, NColor.Red, NColor.White)); visitor.PaintEllipse(bounds.CenterX - bounds.Width / 6, bounds.X + 20, bounds.Width / 3, bounds.Height / 3); base.OnPrePaint(visitor); } #endregion #region Schema /// <summary> /// Schema associated with CustomLabel. /// </summary> public static readonly NSchema CustomLabelSchema; #endregion }

Create a custom label widget

Copy Code

public class CustomLabel : NLabel
{
    #region Constructors

    /// <summary>
    /// Default constructor.
    /// </summary>
    public CustomLabel()
    {
    }
    /// <summary>
    /// Initializing constructor.
    /// </summary>
    /// <param name="text"></param>
    public CustomLabel(string text)
    {
    }

    /// <summary>
    /// Static constructor.
    /// </summary>
    static CustomLabel()
    {
        CustomLabelSchema = NSchema.Create(typeof(CustomLabel), NLabelSchema);
    }

    #endregion

    #region Protected Overrides - Paint

    protected override void OnPrePaint(NPaintVisitor visitor)
    {
        // Paint an ellipse that occupies 1/3rd of the label bounds
        NRectangle bounds = GetContentEdge();
        visitor.SetFill(new NHatchFill(ENHatchStyle.Sphere, NColor.Red, NColor.White));
        visitor.PaintEllipse(bounds.CenterX - bounds.Width / 6, bounds.X + 20, bounds.Width / 3, bounds.Height / 3);

        base.OnPrePaint(visitor);
    }

    #endregion

    #region Schema

    /// <summary>
    /// Schema associated with CustomLabel.
    /// </summary>
    public static readonly NSchema CustomLabelSchema;

    #endregion
}

You can then create a custom label and configure it:

Configure the custom label	Copy Code
CustomLabel label = new CustomLabel("Hello World from Nevron Open Vision"); label.TextAlignment = ENContentAlignment.MiddleCenter; label.PreferredSize = new NSize(400, 200); label.SetBorder(2, NColor.Red);

Configure the custom label

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CustomLabel label = new CustomLabel("Hello World from Nevron Open Vision");
label.TextAlignment = ENContentAlignment.MiddleCenter;
label.PreferredSize = new NSize(400, 200);
label.SetBorder(2, NColor.Red);

This code will result in the following widget: