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Walkthrough: Display QuickInfo tooltips

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QuickInfo is an IntelliSense feature that displays method signatures and descriptions when a user moves the pointer over a method name. You can implement language-based features such as QuickInfo by defining the identifiers for which you want to provide QuickInfo descriptions, and then creating a tooltip in which to display the content. You can define QuickInfo in the context of a language service, or you can define your own file name extension and content type and display the QuickInfo for just that type, or you can display QuickInfo for an existing content type (such as "text"). This walkthrough shows how to display QuickInfo for the "text" content type.

The QuickInfo example in this walkthrough displays the tooltips when a user moves the pointer over a method name. This design requires you to implement these four interfaces:

  • source interface

  • source provider interface

  • controller interface

  • controller provider interface

    The source and controller providers are Managed Extensibility Framework (MEF) component parts, and are responsible for exporting the source and controller classes and importing services and brokers such as the ITextBufferFactoryService, which creates the tooltip text buffer, and the IQuickInfoBroker, which triggers the QuickInfo session.

    In this example, the QuickInfo source uses a hard-coded list of method names and descriptions, but in full implementations, the language service and the language documentation are responsible for providing that content.

Create a MEF project

To create a MEF project

  1. Create a C# VSIX project. (In the New Project dialog, select Visual C# / Extensibility, then VSIX Project.) Name the solution QuickInfoTest.

  2. Add an Editor Classifier item template to the project. For more information, see Create an extension with an editor item template.

  3. Delete the existing class files.

Implement the QuickInfo source

The QuickInfo source is responsible for collecting the set of identifiers and their descriptions and adding the content to the tooltip text buffer when one of the identifiers is encountered. In this example, the identifiers and their descriptions are just added in the source constructor.

To implement the QuickInfo source

  1. Add a class file and name it TestQuickInfoSource.

  2. Add a reference to Microsoft.VisualStudio.Language.IntelliSense.

  3. Add the following imports.

    using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel.Composition;
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;

  4. Declare a class that implements IQuickInfoSource, and name it TestQuickInfoSource.

    internal class TestQuickInfoSource : IQuickInfoSource

  5. Add fields for the QuickInfo source provider, the text buffer, and a set of method names and method signatures. In this example, the method names and signatures are initialized in the TestQuickInfoSource constructor.

    private TestQuickInfoSourceProvider m_provider;
private ITextBuffer m_subjectBuffer;
private Dictionary<string, string> m_dictionary;

  6. Add a constructor that sets the QuickInfo source provider and the text buffer, and populates the set of method names, and method signatures and descriptions.

    public TestQuickInfoSource(TestQuickInfoSourceProvider provider, ITextBuffer subjectBuffer)
{
    m_provider = provider;
    m_subjectBuffer = subjectBuffer;

    //these are the method names and their descriptions
    m_dictionary = new Dictionary<string, string>();
    m_dictionary.Add("add", "int add(int firstInt, int secondInt)\nAdds one integer to another.");
    m_dictionary.Add("subtract", "int subtract(int firstInt, int secondInt)\nSubtracts one integer from another.");
    m_dictionary.Add("multiply", "int multiply(int firstInt, int secondInt)\nMultiplies one integer by another.");
    m_dictionary.Add("divide", "int divide(int firstInt, int secondInt)\nDivides one integer by another.");
}

  7. Implement the AugmentQuickInfoSession method. In this example, the method finds the current word, or the previous word if the cursor is at the end of a line or a text buffer. If the word is one of the method names, the description for that method name is added to the QuickInfo content.

    public void AugmentQuickInfoSession(IQuickInfoSession session, IList<object> qiContent, out ITrackingSpan applicableToSpan)
{
    // Map the trigger point down to our buffer.
    SnapshotPoint? subjectTriggerPoint = session.GetTriggerPoint(m_subjectBuffer.CurrentSnapshot);
    if (!subjectTriggerPoint.HasValue)
    {
        applicableToSpan = null;
        return;
    }

    ITextSnapshot currentSnapshot = subjectTriggerPoint.Value.Snapshot;
    SnapshotSpan querySpan = new SnapshotSpan(subjectTriggerPoint.Value, 0);

    //look for occurrences of our QuickInfo words in the span
    ITextStructureNavigator navigator = m_provider.NavigatorService.GetTextStructureNavigator(m_subjectBuffer);
    TextExtent extent = navigator.GetExtentOfWord(subjectTriggerPoint.Value);
    string searchText = extent.Span.GetText();

    foreach (string key in m_dictionary.Keys)
    {
        int foundIndex = searchText.IndexOf(key, StringComparison.CurrentCultureIgnoreCase);
        if (foundIndex > -1)
        {
            applicableToSpan = currentSnapshot.CreateTrackingSpan
                (
                //querySpan.Start.Add(foundIndex).Position, 9, SpanTrackingMode.EdgeInclusive
                                        extent.Span.Start + foundIndex, key.Length, SpanTrackingMode.EdgeInclusive
                );

            string value;
            m_dictionary.TryGetValue(key, out value);
            if (value != null)
                qiContent.Add(value);
            else
                qiContent.Add("");

            return;
        }
    }

    applicableToSpan = null;
}

  8. You must also implement a Dispose() method, since IQuickInfoSource implements IDisposable:

    private bool m_isDisposed;
public void Dispose()
{
    if (!m_isDisposed)
    {
        GC.SuppressFinalize(this);
        m_isDisposed = true;
    }
}

Implement a QuickInfo source provider

The provider of the QuickInfo source serves primarily to export itself as a MEF component part and instantiate the QuickInfo source. Because it's a MEF component part, it can import other MEF component parts.

To implement a QuickInfo source provider

  1. Declare a QuickInfo source provider named TestQuickInfoSourceProvider that implements IQuickInfoSourceProvider, and export it with a NameAttribute of "ToolTip QuickInfo Source", an OrderAttribute of Before="default", and a ContentTypeAttribute of "text".

    [Export(typeof(IQuickInfoSourceProvider))]
[Name("ToolTip QuickInfo Source")]
[Order(Before = "Default Quick Info Presenter")]
[ContentType("text")]
internal class TestQuickInfoSourceProvider : IQuickInfoSourceProvider

  2. Import two editor services, ITextStructureNavigatorSelectorService and ITextBufferFactoryService, as properties of TestQuickInfoSourceProvider.

    [Import]
internal ITextStructureNavigatorSelectorService NavigatorService { get; set; }

[Import]
internal ITextBufferFactoryService TextBufferFactoryService { get; set; }

  3. Implement TryCreateQuickInfoSource to return a new TestQuickInfoSource.

    public IQuickInfoSource TryCreateQuickInfoSource(ITextBuffer textBuffer)
{
    return new TestQuickInfoSource(this, textBuffer);
}

Implement a QuickInfo controller

QuickInfo controllers determine when QuickInfo is displayed. In this example, QuickInfo appears when the pointer is over a word that corresponds to one of the method names. The QuickInfo controller implements a mouse hover event handler that triggers a QuickInfo session.

To implement a QuickInfo controller

  1. Declare a class that implements IIntellisenseController, and name it TestQuickInfoController.

    internal class TestQuickInfoController : IIntellisenseController

  2. Add private fields for the text view, the text buffers represented in the text view, the QuickInfo session, and the QuickInfo controller provider.

    private ITextView m_textView;
private IList<ITextBuffer> m_subjectBuffers;
private TestQuickInfoControllerProvider m_provider;
private IQuickInfoSession m_session;

  3. Add a constructor that sets the fields and adds the mouse hover event handler.

    internal TestQuickInfoController(ITextView textView, IList<ITextBuffer> subjectBuffers, TestQuickInfoControllerProvider provider)
{
    m_textView = textView;
    m_subjectBuffers = subjectBuffers;
    m_provider = provider;

    m_textView.MouseHover += this.OnTextViewMouseHover;
}

  4. Add the mouse hover event handler that triggers the QuickInfo session.

    private void OnTextViewMouseHover(object sender, MouseHoverEventArgs e)
{
    //find the mouse position by mapping down to the subject buffer
    SnapshotPoint? point = m_textView.BufferGraph.MapDownToFirstMatch
         (new SnapshotPoint(m_textView.TextSnapshot, e.Position),
        PointTrackingMode.Positive,
        snapshot => m_subjectBuffers.Contains(snapshot.TextBuffer),
        PositionAffinity.Predecessor);

    if (point != null)
    {
        ITrackingPoint triggerPoint = point.Value.Snapshot.CreateTrackingPoint(point.Value.Position,
        PointTrackingMode.Positive);

        if (!m_provider.QuickInfoBroker.IsQuickInfoActive(m_textView))
        {
            m_session = m_provider.QuickInfoBroker.TriggerQuickInfo(m_textView, triggerPoint, true);
        }
    }
}

  5. Implement the Detach method so that it removes the mouse hover event handler when the controller is detached from the text view.

    public void Detach(ITextView textView)
{
    if (m_textView == textView)
    {
        m_textView.MouseHover -= this.OnTextViewMouseHover;
        m_textView = null;
    }
}

  6. Implement the ConnectSubjectBuffer method and the DisconnectSubjectBuffer method as empty methods for this example.

    public void ConnectSubjectBuffer(ITextBuffer subjectBuffer)
{
}

public void DisconnectSubjectBuffer(ITextBuffer subjectBuffer)
{
}

Implementing the QuickInfo controller provider

The provider of the QuickInfo controller serves primarily to export itself as a MEF component part and instantiate the QuickInfo controller. Because it's a MEF component part, it can import other MEF component parts.

To implement the QuickInfo controller provider

  1. Declare a class named TestQuickInfoControllerProvider that implements IIntellisenseControllerProvider, and export it with a NameAttribute of "ToolTip QuickInfo Controller" and a ContentTypeAttribute of "text":

    [Export(typeof(IIntellisenseControllerProvider))]
[Name("ToolTip QuickInfo Controller")]
[ContentType("text")]
internal class TestQuickInfoControllerProvider : IIntellisenseControllerProvider

  2. Import the IQuickInfoBroker as a property.

    [Import]
internal IQuickInfoBroker QuickInfoBroker { get; set; }

  3. Implement the TryCreateIntellisenseController method by instantiating the QuickInfo controller.

    public IIntellisenseController TryCreateIntellisenseController(ITextView textView, IList<ITextBuffer> subjectBuffers)
{
    return new TestQuickInfoController(textView, subjectBuffers, this);
}

Build and test the Code

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

To build and test the QuickInfoTest solution

  1. Build the solution.

  2. When you run this project in the debugger, a second instance of Visual Studio is started.

  3. Create a text file and type some text that includes the words "add" and "subtract".

  4. Move the pointer over one of the occurrences of "add". The signature and the description of the add method should be displayed.

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