You can customize the appearance of editor margins by using custom editor extensions. This walkthrough puts a custom glyph on the indicator margin whenever the word "todo" appears in a code comment.
Create a MEF project
Create a C# VSIX project. (In the New Project dialog, select Visual C# / Extensibility, then VSIX Project.) Name the solution TodoGlyphTest.
using System.ComponentModel.Composition;
using System.Windows;
using System.Windows.Shapes;
using System.Windows.Media;
using System.Windows.Controls;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Formatting;
using Microsoft.VisualStudio.Text.Tagging;
using Microsoft.VisualStudio.Utilities;
public UIElement GenerateGlyph(IWpfTextViewLine line, IGlyphTag tag)
{
// Ensure we can draw a glyph for this marker.
if (tag == null || !(tag is TodoTag))
{
return null;
}
System.Windows.Shapes.Ellipse ellipse = new Ellipse();
ellipse.Fill = Brushes.LightBlue;
ellipse.StrokeThickness = 2;
ellipse.Stroke = Brushes.DarkBlue;
ellipse.Height = m_glyphSize;
ellipse.Width = m_glyphSize;
return ellipse;
}
Public Function GenerateGlyph(ByVal line As IWpfTextViewLine, ByVal tag As IGlyphTag) As System.Windows.UIElement Implements IGlyphFactory.GenerateGlyph
' Ensure we can draw a glyph for this marker.
If tag Is Nothing OrElse Not (TypeOf tag Is TodoTag) Then
Return Nothing
End If
Dim ellipse As Ellipse = New Ellipse()
ellipse.Fill = Brushes.LightBlue
ellipse.StrokeThickness = 2
ellipse.Stroke = Brushes.DarkBlue
ellipse.Height = m_glyphSize
ellipse.Width = m_glyphSize
Return ellipse
End Function
public IGlyphFactory GetGlyphFactory(IWpfTextView view, IWpfTextViewMargin margin)
{
return new TodoGlyphFactory();
}
Public Function GetGlyphFactory(ByVal view As IWpfTextView, ByVal margin As IWpfTextViewMargin) As IGlyphFactory Implements IGlyphFactoryProvider.GetGlyphFactory
Return New TodoGlyphFactory()
End Function
Define a Todo tag and tagger
Define the relationship between the UI element that you defined in the previous steps and the indicator margin. Create a tag type and tagger and export it by using a tagger provider.
To define a todo tag and tagger
Add a new class file to the project and name it TodoTagger.
using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Tagging;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Classification;
using Microsoft.VisualStudio.Utilities;
Friend Sub New(ByVal classifier As IClassifier)
m_classifier = classifier
End Sub
Implement the GetTags method by finding all the classification spans whose names include the word "comment" and whose text includes the search text. Whenever the search text is found, yield back a new TagSpan<T> of type TodoTag.
IEnumerable<ITagSpan<TodoTag>> ITagger<TodoTag>.GetTags(NormalizedSnapshotSpanCollection spans)
{
foreach (SnapshotSpan span in spans)
{
//look at each classification span \
foreach (ClassificationSpan classification in m_classifier.GetClassificationSpans(span))
{
//if the classification is a comment
if (classification.ClassificationType.Classification.ToLower().Contains("comment"))
{
//if the word "todo" is in the comment,
//create a new TodoTag TagSpan
int index = classification.Span.GetText().ToLower().IndexOf(m_searchText);
if (index != -1)
{
yield return new TagSpan<TodoTag>(new SnapshotSpan(classification.Span.Start + index, m_searchText.Length), new TodoTag());
}
}
}
}
}
Private Function GetTags(ByVal spans As NormalizedSnapshotSpanCollection) As IEnumerable(Of ITagSpan(Of TodoTag)) Implements ITagger(Of TodoTag).GetTags
Dim list As List(Of ITagSpan(Of TodoTag))
list = New List(Of ITagSpan(Of TodoTag))()
For Each span As SnapshotSpan In spans
'look at each classification span \
For Each classification As ClassificationSpan In m_classifier.GetClassificationSpans(span)
'if the classification is a comment
If classification.ClassificationType.Classification.ToLower().Contains("comment") Then
'if the word "todo" is in the comment,
'create a new TodoTag TagSpan
Dim index As Integer = classification.Span.GetText().ToLower().IndexOf(m_searchText)
If index <> -1 Then
list.Add(New TagSpan(Of TodoTag)(New SnapshotSpan(classification.Span.Start + index, m_searchText.Length), New TodoTag()))
End If
End If
Next classification
Next span
Return list
End Function
public event EventHandler<SnapshotSpanEventArgs> TagsChanged;
Public Event TagsChanged(ByVal sender As Object, ByVal e As Microsoft.VisualStudio.Text.SnapshotSpanEventArgs) Implements Microsoft.VisualStudio.Text.Tagging.ITagger(Of TodoTag).TagsChanged
public ITagger<T> CreateTagger<T>(ITextBuffer buffer) where T : ITag
{
if (buffer == null)
{
throw new ArgumentNullException("buffer");
}
return new TodoTagger(AggregatorService.GetClassifier(buffer)) as ITagger<T>;
}
Public Function CreateTagger(Of T As Microsoft.VisualStudio.Text.Tagging.ITag)(ByVal buffer As Microsoft.VisualStudio.Text.ITextBuffer) As Microsoft.VisualStudio.Text.Tagging.ITagger(Of T) Implements Microsoft.VisualStudio.Text.Tagging.ITaggerProvider.CreateTagger
If buffer Is Nothing Then
Throw New ArgumentNullException("buffer")
End If
Return TryCast(New TodoTagger(AggregatorService.GetClassifier(buffer)), ITagger(Of T))
End Function
Build and test the code
To test this code, build the TodoGlyphTest solution and run it in the experimental instance.
To build and test the TodoGlyphTest solution
Build the solution.
Run the project by pressing F5. A second instance of Visual Studio starts.
Make sure that the indicator margin is showing. (On the Tools menu, click Options. On the Text Editor page, make sure that Indicator margin is selected.)
Open a code file that has comments. Add the word "todo" to one of the comment sections.
A light blue circle with a dark blue outline appears in the indicator margin to the left of the code window.