Controls / Syntax Editor / Features

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Layers

RadSyntaxEditor renders its elements on different layers based on the types of tags that are used. It does so with the help of a UILayersBuilder class. The default builder renders the following stack of layers:

  • TextHighlightUILayer
  • TextBorderUILayer
  • TextUnderlineUILayer
  • TextUILayer
  • TextToolTipUILayer
  • SelectionUILayer
  • FoldingUILayer

These layers are responsible for drawing different elements on the canvas of the RadSyntaxEditor control. For example, the FoldingUILayer generates a FoldedRegionButton with a tool-tip, containing the folded text.

Custom Layer and UILayersBuilder

We will now create a custom layer which will be responsible for highlighting any comments in the code. For the purpose, we need to override the GetLinePartUIElement method and return a FrameworkElement to be drawn on the layer - a LightGray rectangle in this case.

Creating a custom layer


public class CommentsUILayer : LineBasedUILayer<Telerik.WinForms.SyntaxEditor.Core.Tagging.ClassificationTag>
{
    public override string Name
    {
        get
        {
            return "UnderlineOnMouseOver";
        }
    }

    public CommentsUILayer()
    {
    }

    protected override FrameworkElement GetLinePartUIElement(Telerik.WinForms.SyntaxEditor.Core.Tagging.ClassificationTag tag,
        Telerik.WinForms.SyntaxEditor.Core.Text.Span span, UIUpdateContext updateContext)
    {
        if (tag.ClassificationType != Telerik.WinForms.SyntaxEditor.Core.Tagging.ClassificationTypes.Comment)
        {
            return null;
        }

        Rect rect = updateContext.Editor.GetLinePartBoundingRectangle(span);
        Telerik.WinControls.SyntaxEditor.UI.Rectangle rectangle = this.GetElementFromPool<Telerik.WinControls.SyntaxEditor.UI.Rectangle>();
        rectangle.ShouldHandleMouseInput = true;
        rectangle.Width = rect.Width;
        rectangle.Height = rect.Height;
        rectangle.Fill = new SolidBrush(System.Drawing.Color.FromArgb(100, System.Drawing.Color.LightGray));

        return rectangle;
    }

    protected override void ResetPooledElementProperties(object element)
    {
        Telerik.WinControls.SyntaxEditor.UI.Rectangle rectangle = (Telerik.WinControls.SyntaxEditor.UI.Rectangle)element;
        rectangle.ClearValue(Telerik.WinControls.SyntaxEditor.UI.Rectangle.FillProperty);
    }
}

For our custom layer to be recognized by the RadSyntaxEditor we need to add it to the UILayerStack. We can do so by creating a custom UILayersBuilder and overriding its BuildUILayers method.

Using the custom layer in a custom layers builder


public class CustomUILayersBuilder : Telerik.WinForms.Controls.SyntaxEditor.UI.Layers.UILayersBuilder
{
    private CommentsUILayer customLayer;
    public override void BuildUILayers(UILayerStack uiLayers)
            {
                base.BuildUILayers(uiLayers);

                customLayer = new CommentsUILayer();
                uiLayers.AddLast(customLayer);
            }

    public void ClearCustomLayer()
    {
        foreach (Telerik.WinControls.SyntaxEditor.UI.Rectangle item in this.customLayer.Container.Children.OfType<Telerik.WinControls.SyntaxEditor.UI.Rectangle>())
        {
            item.Fill = System.Drawing.Brushes.Transparent;
        }
    }
}

Finally, we need to set the UILayersBuilder to an instance of the custom layers builder class.

Using the custom layers builder


this.radSyntaxEditor1.SyntaxEditorElement.UILayersBuilder = new CustomUILayersBuilder();

Consider that we have the following taggers applied to RadSyntaxEditor:

            CSharpTagger currentLanguageTagger = new Telerik.WinForms.Controls.SyntaxEditor.Tagging.Taggers.CSharpTagger(this.radSyntaxEditor1.SyntaxEditorElement);
            this.radSyntaxEditor1.TaggersRegistry.RegisterTagger(currentLanguageTagger);

            CSharpFoldingTagger foldingTagger = new Telerik.WinForms.Controls.SyntaxEditor.Taggers.CSharpFoldingTagger(this.radSyntaxEditor1.SyntaxEditorElement);
            foldingTagger.FoldingRegionDefinitions.Add(new FoldingRegionDefinition("#if", "#endif"));

Once you run the application, the comments are expected to be colored as it is illustrated below:

Figure 1: Default comments' style

WinForms RadSyntaxEditor Default comments' style

Figure 2: Custom layer for comments

WinForms RadSyntaxEditor Custom layer for comments

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