Custom Tagger

To create a custom tagger, you can inherit from the abstract generic TaggerBase class. You then need to implement the abstract GetTags method which is responsible for acquiring all spans of tags which meet a specific condition.

To demonstrate this we will create the following class which shows a tooltip on all occurrences of a specified search word.

Example 1: Registering taggers

• C#

public class SimpleToolTipTagger : TaggerBase<ToolTipTag> 
{ 
    private string searchWord; 
 
    public SimpleToolTipTagger(ITextDocumentEditor editor) 
        : base(editor) 
    { 
    } 
 
    public override IEnumerable<TagSpan<ToolTipTag>> GetTags(NormalizedSnapshotSpanCollection spans) 
    { 
        if (string.IsNullOrEmpty(this.searchWord)) 
        { 
            yield break; 
        } 
 
        TextSnapshot snapshot = this.Document.CurrentSnapshot; 
        foreach (TextSnapshotSpan snapshotSpan in spans) 
        { 
            string lineString = snapshotSpan.GetText(); 
            int index = lineString.IndexOf(this.searchWord); 
            while (index != -1) 
            { 
                TextSnapshotSpan tempSnapshotSpan = new TextSnapshotSpan(snapshot, 
                    new Span(snapshotSpan.Start + index, searchWord.Length)); 
 
                yield return new TagSpan<ToolTipTag>(tempSnapshotSpan, new ToolTipTag("Sample tooltip " + searchWord)); 
 
                index = lineString.IndexOf(this.searchWord, index + this.searchWord.Length); 
            } 
        } 
    } 
 
    public void UpdateSearchWord(string newSearchWord) 
    { 
        this.searchWord = newSearchWord; 
        this.CallOnTagsChanged(this.Document.CurrentSnapshot.Span); 
    } 
} 

To use the tagger you need to register it in the TaggersRegistry as you would do with any other tagger. You can then call the UpdateSearchWord method to apply the tagger to any spans containing a specific word.

Example 2: Using the custom tagger

• C#

var simpleToolTipTagger = new SimpleToolTipTagger(this.syntaxEditor); 
if (!this.syntaxEditor.TaggersRegistry.IsTaggerRegistered(simpleToolTipTagger)) 
{ 
    this.syntaxEditor.TaggersRegistry.RegisterTagger(this.simpleToolTipTagger); 
} 
simpleToolTipTagger.UpdateSearchWord("Telerik"); 

Figure 1: The custom tooltip tagger