Walkthrough: Displaying SmartTags

Article
12/19/2012

Smart tags are tags on text that expand to display a set of actions. For example, in a Visual Basic or Visual C# project, a red line appears under a word when you rename an identifier such as a variable name. When you move the pointer over the underline, a button is displayed near the pointer. If you click the button, a suggested action is displayed, for example, Rename IsRead to IsReady. If you click the action, all references to IsRead in the project are renamed IsReady.

Although smart tags are part of the IntelliSense implementation in the editor, you can implement smart tags by subclassing SmartTag, and then implementing the ITagger<T> interface and the IViewTaggerProvider interface.

Note

Other kinds of tags can be implemented in a similar manner.

The following walkthrough shows how to create a smart tag that appears on the current word and has two suggested actions: Convert to upper case and Convert to lower case.

Prerequisites

To complete this walkthrough, you must install the Visual Studio 2012 SDK.

Note

For more information about the Visual Studio SDK, see Extending Visual Studio Overview. To find out how to download the Visual Studio SDK, see Visual Studio Extensibility Developer Center on the MSDN Web site.

Creating a Managed Extensibility Framework (MEF) Project

To create a MEF project

Create an Editor Classifier project. Name the solution SmartTagTest.
Open the source.extension.vsixmanifest file in the VSIX Manifest Editor.
Make sure that the Content heading contains a MEF Component content type and that the Path is set to SmartTagTest.dll.
Save and close source.extension.vsixmanifest.
Add the following reference to the project, and set CopyLocal to false:

Microsoft.VisualStudio.Language.Intellisense
Delete the existing class files.

Implementing a Tagger for Smart Tags

To implement a tagger for smart tags

Add a class file and name it TestSmartTag.

Add the following imports:

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel.Composition
Imports System.Collections.ObjectModel
Imports System.Windows.Media
Imports Microsoft.VisualStudio.Language.Intellisense
Imports Microsoft.VisualStudio.Text
Imports Microsoft.VisualStudio.Text.Editor
Imports Microsoft.VisualStudio.Text.Operations
Imports Microsoft.VisualStudio.Text.Tagging
Imports Microsoft.VisualStudio.Utilities

using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.Collections.ObjectModel;
using System.Windows.Media;
using Microsoft.VisualStudio.Language.Intellisense;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Operations;
using Microsoft.VisualStudio.Text.Tagging;
using Microsoft.VisualStudio.Utilities;

Add a class named TestSmartTag that inherits from SmartTag.

Friend Class TestSmartTag
    Inherits SmartTag

internal class TestSmartTag : SmartTag

Add a constructor for this class that calls the base constructor with a SmartTagType of Factoid, which will cause a blue line to appear under the first character of a word. (If you use Ephemeral, a red line will appear under the last character of the word.)

Public Sub New(ByVal actionSets As ReadOnlyCollection(Of SmartTagActionSet))
    MyBase.New(SmartTagType.Factoid, actionSets)
End Sub

public TestSmartTag(ReadOnlyCollection<SmartTagActionSet> actionSets) :
    base(SmartTagType.Factoid, actionSets) { }

Add a class named TestSmartTagger that inherits from ITagger<T> of type TestSmartTag, and implements IDisposable.

Friend Class TestSmartTagger
    Implements ITagger(Of TestSmartTag), IDisposable

internal class TestSmartTagger : ITagger<TestSmartTag>, IDisposable

Add the following private fields to the tagger class.

Private m_buffer As ITextBuffer
Private m_view As ITextView
Private m_provider As TestSmartTaggerProvider
Private m_disposed As Boolean

private ITextBuffer m_buffer;
private ITextView m_view;
private TestSmartTaggerProvider m_provider;
private bool m_disposed;

Add a constructor that sets the private fields, and subscribes to the LayoutChanged event.

Public Sub New(ByVal buffer As ITextBuffer, ByVal view As ITextView, ByVal provider As TestSmartTaggerProvider)
    m_buffer = buffer
    m_view = view
    m_provider = provider
    AddHandler m_view.LayoutChanged, AddressOf OnLayoutChanged
End Sub

public TestSmartTagger(ITextBuffer buffer, ITextView view, TestSmartTaggerProvider provider)
{
    m_buffer = buffer;
    m_view = view;
    m_provider = provider;
    m_view.LayoutChanged += OnLayoutChanged;
}

Implement GetTags so that the tag is created for the current word. (This method also calls a private method GetSmartTagActions that is explained later.)

Public Function GetTags(ByVal spans As NormalizedSnapshotSpanCollection) As IEnumerable(Of ITagSpan(Of TestSmartTag)) Implements ITagger(Of TestSmartTag).GetTags
    Dim snapshot As ITextSnapshot = m_buffer.CurrentSnapshot
    If snapshot.Length = 0 Then 
        Return Nothing 
        Exit Function 
    End If 

    'set up the navigator 
    Dim navigator As ITextStructureNavigator = m_provider.NavigatorService.GetTextStructureNavigator(m_buffer)

    'set up a list to contain the tags 
    Dim list As List(Of TagSpan(Of TestSmartTag))
    list = New List(Of TagSpan(Of TestSmartTag))()

    For Each span In spans
        Dim caret As ITextCaret = m_view.Caret
        Dim point As SnapshotPoint

        If CInt(caret.Position.BufferPosition) > 0 Then
            point = caret.Position.BufferPosition - 1
        Else 
            Exit For 
        End If 

        Dim extent As TextExtent = navigator.GetExtentOfWord(point)
        'don't display the tag if the extent has whitespace 
        If extent.IsSignificant Then
            list.Add(New TagSpan(Of TestSmartTag)(extent.Span, New TestSmartTag(GetSmartTagActions(extent.Span))))
        Else 
            Exit For 
        End If 
    Next span

    Return list
End Function

public IEnumerable<ITagSpan<TestSmartTag>> GetTags(NormalizedSnapshotSpanCollection spans)
{
    ITextSnapshot snapshot = m_buffer.CurrentSnapshot;
    if (snapshot.Length == 0)
        yield break; //don't do anything if the buffer is empty 

    //set up the navigator
    ITextStructureNavigator navigator = m_provider.NavigatorService.GetTextStructureNavigator(m_buffer);

    foreach (var span in spans)
    {
        ITextCaret caret = m_view.Caret;
        SnapshotPoint point;

        if (caret.Position.BufferPosition > 0)
            point = caret.Position.BufferPosition - 1;
        else 
            yield break;

        TextExtent extent = navigator.GetExtentOfWord(point);
        //don't display the tag if the extent has whitespace 
        if (extent.IsSignificant)
            yield return new TagSpan<TestSmartTag>(extent.Span, new TestSmartTag(GetSmartTagActions(extent.Span)));
        else yield break;
    }
}

Add a GetSmartTagActions method to set up the smart tag actions. The actions themselves are implemented in later steps.

Private Function GetSmartTagActions(ByVal span As SnapshotSpan) As ReadOnlyCollection(Of SmartTagActionSet)
    Dim actionSetList As New List(Of SmartTagActionSet)()
    Dim actionList As New List(Of ISmartTagAction)()

    Dim trackingSpan As ITrackingSpan = span.Snapshot.CreateTrackingSpan(span, SpanTrackingMode.EdgeInclusive)
    actionList.Add(New UpperCaseSmartTagAction(trackingSpan))
    actionList.Add(New LowerCaseSmartTagAction(trackingSpan))
    Dim actionSet As New SmartTagActionSet(actionList.AsReadOnly())
    actionSetList.Add(actionSet)
    Return actionSetList.AsReadOnly()
End Function

private ReadOnlyCollection<SmartTagActionSet> GetSmartTagActions(SnapshotSpan span)
{
    List<SmartTagActionSet> actionSetList = new List<SmartTagActionSet>();
    List<ISmartTagAction> actionList = new List<ISmartTagAction>();

    ITrackingSpan trackingSpan = span.Snapshot.CreateTrackingSpan(span, SpanTrackingMode.EdgeInclusive);
    actionList.Add(new UpperCaseSmartTagAction(trackingSpan));
    actionList.Add(new LowerCaseSmartTagAction(trackingSpan));
    SmartTagActionSet actionSet = new SmartTagActionSet(actionList.AsReadOnly());
    actionSetList.Add(actionSet);
    return actionSetList.AsReadOnly();
}

Declare the SmartTagsChanged event.

Public Event TagsChanged As EventHandler(Of SnapshotSpanEventArgs) Implements ITagger(Of TestSmartTag).TagsChanged

public event EventHandler<SnapshotSpanEventArgs> TagsChanged;

Implement the OnLayoutChanged event handler to raise the TagsChanged event, which causes GetTags to be called.

Private Sub OnLayoutChanged(ByVal sender As Object, ByVal e As TextViewLayoutChangedEventArgs)
    Dim snapshot As ITextSnapshot = e.NewSnapshot
    'don't do anything if this is just a change in case 
    If Not snapshot.GetText().ToLower().Equals(e.OldSnapshot.GetText().ToLower()) Then 
        Dim span As New SnapshotSpan(snapshot, New Span(0, snapshot.Length))
        Dim handler As EventHandler(Of SnapshotSpanEventArgs) = Me.TagsChangedEvent
        If handler IsNot Nothing Then
            handler(Me, New SnapshotSpanEventArgs(span))
        End If 
    End If 
End Sub

private void OnLayoutChanged(object sender, TextViewLayoutChangedEventArgs e)
{
    ITextSnapshot snapshot = e.NewSnapshot;
    //don't do anything if this is just a change in case 
    if (!snapshot.GetText().ToLower().Equals(e.OldSnapshot.GetText().ToLower()))
    {
        SnapshotSpan span = new SnapshotSpan(snapshot, new Span(0, snapshot.Length));
        EventHandler<SnapshotSpanEventArgs> handler = this.TagsChanged;
        if (handler != null)
        {
            handler(this, new SnapshotSpanEventArgs(span));
        }
    }
}

Implement the Dispose method so that it unsubscribes from the LayoutChanged event.

Public Sub Dispose() Implements IDisposable.Dispose
    Dispose(True)
    GC.SuppressFinalize(Me)
End Sub 

Private Sub Dispose(ByVal disposing As Boolean)
    If disposing Then 
        RemoveHandler m_view.LayoutChanged, AddressOf OnLayoutChanged
        m_view = Nothing 
    End If

    m_disposed = True 
End Sub

public void Dispose()
{
    Dispose(true);
    GC.SuppressFinalize(this);
}

private void Dispose(bool disposing)
{
    if (!this.m_disposed)
    {
        if (disposing)
        {
            m_view.LayoutChanged -= OnLayoutChanged;
            m_view = null;
        }

        m_disposed = true;
    }
}

Implementing the Smart Tag Tagger Provider

To implement the smart tag tagger provider

Add a class named TestSmartTagTaggerProvider that inherits from IViewTaggerProvider. Export it with a ContentTypeAttribute of "text", a OrderAttribute of Before="default", and a TagTypeAttribute of SmartTag.

<Export(GetType(IViewTaggerProvider))>
<ContentType("text")>
<Order(Before:="default")>
<TagType(GetType(SmartTag))>
Friend Class TestSmartTaggerProvider
    Implements IViewTaggerProvider

[Export(typeof(IViewTaggerProvider))]
[ContentType("text")]
[Order(Before = "default")]
[TagType(typeof(SmartTag))]
internal class TestSmartTaggerProvider : IViewTaggerProvider

Import the ITextStructureNavigatorSelectorService as a property.

<Import(GetType(ITextStructureNavigatorSelectorService))>
Friend Property NavigatorService() As ITextStructureNavigatorSelectorService

[Import(typeof(ITextStructureNavigatorSelectorService))]
internal ITextStructureNavigatorSelectorService NavigatorService { get; set; }

Implement the CreateTagger<T> method.

Public Function CreateTagger(Of T As ITag)(ByVal textView As ITextView, ByVal buffer As ITextBuffer) As ITagger(Of T) Implements IViewTaggerProvider.CreateTagger
    If buffer Is Nothing OrElse textView Is Nothing Then 
        Return Nothing 
    End If 

    'make sure we are tagging only the top buffer 
    If buffer Is textView.TextBuffer Then 
        Return New TestSmartTagger(buffer, textView, Me)
    Else 
        Return Nothing 
    End If 
End Function

public ITagger<T> CreateTagger<T>(ITextView textView, ITextBuffer buffer) where T : ITag
{
    if (buffer == null || textView == null)
    {
        return null;
    }

    //make sure we are tagging only the top buffer 
    if (buffer == textView.TextBuffer)
    {
        return new TestSmartTagger(buffer, textView, this) as ITagger<T>;
    }
    else return null;
}

Implementing Smart Tag Actions

To implement smart tag actions

Create two classes, the first named UpperCaseSmartTagAction and the second named LowerCaseSmartTagAction. Both classes implement ISmartTagAction.

Friend Class UpperCaseSmartTagAction
    Implements ISmartTagAction

internal class UpperCaseSmartTagAction : ISmartTagAction

Friend Class LowerCaseSmartTagAction
    Implements ISmartTagAction

internal class LowerCaseSmartTagAction : ISmartTagAction

Both classes are alike except that one calls ToUpper and the other calls ToLower. The following steps cover only the uppercase action class, but you must implement both classes. Use the steps for implementing the uppercase action as a pattern for implementing the lowercase action.

Declare a set of private fields.

Private m_span As ITrackingSpan
Private m_upper As String 
Private m_display As String 
Private m_snapshot As ITextSnapshot

private ITrackingSpan m_span;
private string m_upper;
private string m_display;
private ITextSnapshot m_snapshot;

Add a constructor that sets the fields.

Public Sub New(ByVal span As ITrackingSpan)
    m_span = span
    m_snapshot = span.TextBuffer.CurrentSnapshot
    m_upper = span.GetText(m_snapshot).ToUpper()
    m_display = "Convert to upper case" 
End Sub

public UpperCaseSmartTagAction(ITrackingSpan span)
{
    m_span = span;
    m_snapshot = span.TextBuffer.CurrentSnapshot;
    m_upper = span.GetText(m_snapshot).ToUpper();
    m_display = "Convert to upper case";
}

Implement the properties as follows.

Public ReadOnly Property DisplayText() As String Implements ISmartTagAction.DisplayText
    Get 
        Return m_display
    End Get 
End Property 
Public ReadOnly Property Icon() As ImageSource Implements ISmartTagAction.Icon
    Get 
        Return Nothing 
    End Get 
End Property 
Public ReadOnly Property IsEnabled() As Boolean Implements ISmartTagAction.IsEnabled
    Get 
        Return True 
    End Get 
End Property 

Private privateSource As ISmartTagSource
Public Property Source() As ISmartTagSource
    Get 
        Return privateSource
    End Get 
    Private Set(ByVal value As ISmartTagSource)
        privateSource = value
    End Set 
End Property 

Public ReadOnly Property ActionSets() As ReadOnlyCollection(Of SmartTagActionSet) Implements ISmartTagAction.ActionSets
    Get 
        Return Nothing 
    End Get 
End Property

public string DisplayText
{
    get { return m_display; }
}
public ImageSource Icon
{
    get { return null; }
}
public bool IsEnabled
{
    get { return true; }
}

public ISmartTagSource Source
{
    get;
    private set;
}

public ReadOnlyCollection<SmartTagActionSet> ActionSets
{
    get { return null; }
}

Implement the Invoke method by replacing the text in the span with its uppercase equivalent.

Public Sub Invoke() Implements ISmartTagAction.Invoke
    m_span.TextBuffer.Replace(m_span.GetSpan(m_snapshot), m_upper)
End Sub

public void Invoke()
{
    m_span.TextBuffer.Replace(m_span.GetSpan(m_snapshot), m_upper);
}

Building and Testing the Code

To test this code, build the SmartTagTest solution and run it in the experimental instance.

To build and test the SmartTagTest solution

Build the solution.
When you run this project in the debugger, a second instance of Visual Studio is instantiated.
Create a text file and type some text.

A blue line should be displayed under the first letter of the first word of the text.
Move the pointer over the blue line.

A button should be displayed near the pointer.
When you click the button, two suggested actions should be displayed: Convert to upper case and Convert to lower case. If you click the first action, all the text in the current word should be converted to upper case. If you click the second action, all the text should be converted to lower case.

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