How to get active IWpfTextView in VS2019 extension (MEF)

Question

I'm trying to get the active C# Editor IWpfTextView in VS2019 extension. I'm using a small MEF service to inject a view into the VSAsyncPackage. But it is not very reliable - sometimes the injected view is wrong (e.g. from another view) or missing. Here is the service:

public interface IActiveViewAccessor
{
    IWpfTextView? ActiveView { get; }
}

[Export(typeof(IWpfTextViewConnectionListener))]
[Export(typeof(IActiveViewAccessor))]
[ContentType("text")]
[TextViewRole(PredefinedTextViewRoles.Document)]
internal sealed class ActiveViewConnectionListener : IWpfTextViewConnectionListener, IActiveViewAccessor
    {
    public IWpfTextView? ActiveView { get; private set; }

    public void SubjectBuffersConnected(IWpfTextView textView, ConnectionReason reason, Collection<ITextBuffer> subjectBuffers)
    {
        this.ActiveView = textView;
    }

    public void SubjectBuffersDisconnected(IWpfTextView textView, ConnectionReason reason, Collection<ITextBuffer> subjectBuffers)
    {
        this.ActiveView = null;
    }
}

This service is being injected into the VSPackage as:

this.viewAccessor = this.exportProvider.GetExportedValue<IActiveViewAccessor>();

and it is being used as:

var view = this.viewAccessor?.ActiveView;

Is there a better and more stable way to get IWpfTextView in the async VSPackage?

So far, here are some related questions but not exactly what I'd expected:

I suggest you could add an answer about your tips rather than in the question. — Mr Qian, Dec 28 '20 at 09:44
@PerryQian-MSFT I was not entirely sure about the "modern" or "right" way of accessing the active IWpfTextView, but your suggestion makes sense, thanks. Done. — Pavel Sapehin, Dec 28 '20 at 15:17

score 2 · Accepted Answer · answered Dec 28 '20 at 15:09

After a bit of debugging and exploring, I concluded that my initial approach is very naive. Because IWpfTextViewConnectionListener is only firing once per editor window in a simple case, and it's not firing during switching between already connected views.

After experimenting with it and sneaking into VsVim > VsAdapter.cs I've changed IActiveViewAccessor to the this:

public interface IActiveViewAccessor
{
    IWpfTextView? ActiveView { get; }
}

[Export(typeof(IActiveViewAccessor))]
internal sealed class ActiveViewAccessor : IActiveViewAccessor
{
    private readonly SVsServiceProvider serviceProvider;
    private readonly IVsEditorAdaptersFactoryService editorAdaptersFactoryService;

    [ImportingConstructor]
    public ActiveViewAccessor(
        SVsServiceProvider vsServiceProvider,
        IVsEditorAdaptersFactoryService editorAdaptersFactoryService)
    {
        this.serviceProvider = vsServiceProvider;
        this.editorAdaptersFactoryService = editorAdaptersFactoryService;
    }

    public IWpfTextView? ActiveView
    {
        get
        {
            IVsTextManager2 textManager =
                serviceProvider.GetService<SVsTextManager, IVsTextManager2>();

            if (textManager == null)
            {
                return null;
            }

            int hr = textManager.GetActiveView2(
                fMustHaveFocus: 1,
                pBuffer: null,
                grfIncludeViewFrameType: (uint)_VIEWFRAMETYPE.vftCodeWindow,
                ppView: out IVsTextView vsTextView);

            if (ErrorHandler.Failed(hr))
            {
                return null;
            }

            return editorAdaptersFactoryService.GetWpfTextView(vsTextView);
        }
    }
}

How to get active IWpfTextView in VS2019 extension (MEF)

1 Answers1

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