VS Extension+NVelocity系列(三)——让VS支持 NVelocity的智能提示（中）

internal static class NVDefinition
{
    public const string ContentType = "vm";

    public const string FileExtension = ".vm";

    [Export]
    [Name("vm")]
    [BaseDefinition("HTML")]
    internal static ContentTypeDefinition nvContentTypeDefinition = null;

    [Export]
    [FileExtension(FileExtension)]
    [ContentType("vm")]
    internal static FileExtensionToContentTypeDefinition nvFileExtensionDefinition = null;
}

[Export(typeof(IVsTextViewCreationListener))]
[ContentType(NVExtension.ContentType)]
[TextViewRole(PredefinedTextViewRoles.Interactive)]
[FileExtension(NVExtension.FileExtension)]
internal sealed class VsTextViewCreationListener : IVsTextViewCreationListener
{
    [Import]
    IVsEditorAdaptersFactoryService AdaptersFactory = null;

    [Import]
    ICompletionBroker CompletionBroker = null;

    public void VsTextViewCreated(IVsTextView textViewAdapter)
    {
        IWpfTextView textView = AdaptersFactory.GetWpfTextView(textViewAdapter);
        IOleCommandTarget next = null;
        VMCommandFilter filter = new VMCommandFilter(textView, CompletionBroker, next);
        textViewAdapter.AddCommandFilter(filter, out next);
    }
}

internal sealed class VMCommandFilter : IOleCommandTarget
{
    /// <summary>
    /// 当前会话
    /// </summary>
    ICompletionSession _CurrentSession;

    /// <summary>
    /// TextView(WPF)
    /// </summary>
    IWpfTextView _TextView { get; private set; }

    /// <summary>
    /// 代理
    /// </summary>
    ICompletionBroker _Broker { get; private set; }

    /// <summary>
    /// 执行由VMCommandFilter未执行完的命令
    /// </summary>
    IOleCommandTarget _Next { get; set; }

    public VMCommandFilter(IWpfTextView textView, ICompletionBroker broker, IOleCommandTarget next)
    {
        this._TextView = textView;
        this._Broker = broker;
        this._Next = next;
    }

    /// <summary>
    /// 获取输入的字符
    /// </summary>
    /// <param name="pvaIn">输入指针</param>
    private char GetTypeChar(IntPtr pvaIn)
    {
        return (char)(ushort)Marshal.GetObjectForNativeVariant(pvaIn);
    }

    /// <summary>
    /// 执行指定的命令
    /// </summary>
    /// <param name="pguidCmdGroup">命令组的 GUID</param>
    /// <param name="nCmdID">命令 ID</param>
    /// <param name="nCmdexecopt">指定对象应如何执行命令</param>
    /// <param name="pvaIn">命令的输入参数</param>
    /// <param name="pvaOut">命令的输出参数</param>
    public int Exec(ref Guid pguidCmdGroup, uint nCmdID, uint nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut)
    {
        int hresult = VSConstants.S_OK;
        char inputChar = Char.MinValue;
        if (pguidCmdGroup == VSConstants.VSStd2K)
        {
            VSConstants.VSStd2KCmdID cmd = (VSConstants.VSStd2KCmdID)nCmdID;

            if (cmd == VSConstants.VSStd2KCmdID.RETURN //按下回车
                ||
                cmd == VSConstants.VSStd2KCmdID.TAB //按下Tab
                )
            {
                Complete(true);
            }
            else//尚未被处理
            {
                hresult = _Next.Exec(ref pguidCmdGroup, nCmdID, nCmdexecopt, pvaIn, pvaOut); //由VS现行处理此条命令.
                //确认hresult是否是成功处理的
                if (ErrorHandler.Succeeded(hresult))
                {                    
                    if (cmd == VSConstants.VSStd2KCmdID.TYPECHAR) //字符键入
                    {
		    //获取输入值
                    inputChar = GetTypeChar(pvaIn);
                        //如果当前的会话已经被启动
                        if (_CurrentSession != null && _CurrentSession.IsStarted)
                        {
                            //执行过滤
                            _CurrentSession.SelectedCompletionSet.Filter();
                            //选择最佳匹配
                            _CurrentSession.SelectedCompletionSet.SelectBestMatch();
                            //重新计算CompletionSet
                            _CurrentSession.SelectedCompletionSet.Recalculate();
                        }
                        else if (inputChar == ‘$‘) //如果是键入了$字符
                        {
                            //获取插入符号,也就是光标位置.
                            SnapshotPoint caret = _TextView.Caret.Position.BufferPosition;
                            //文本快照
                            ITextSnapshot snapShot = caret.Snapshot;
                            //在当前插入符号位置创建积极的跟踪点
                            ITrackingPoint trackingPoint = snapShot.CreateTrackingPoint(caret, PointTrackingMode.Positive);
                            //由代理创建Completion会话
                            _CurrentSession = _Broker.CreateCompletionSession(_TextView, trackingPoint, true);
                            //启动该会话.
                            _CurrentSession.Start();
                            //添加放弃事件
                            _CurrentSession.Dismissed += (sender, args) => _CurrentSession = null;
                        }
                    }
                    else if (
                        cmd == VSConstants.VSStd2KCmdID.BACKSPACE //删除键
                        ||
                        cmd == VSConstants.VSStd2KCmdID.DELETE //删除键
                        )
                    {
                        //如果当前会话并未丢弃,执行过滤
                        if (_CurrentSession != null && !_CurrentSession.IsDismissed)
                            _CurrentSession.Filter();
                    }
                }
            }
        }
        return hresult;
    }

    /// <summary>
    /// 查询该对象以获得由用户界面事件生成的一个或多个命令的状态
    /// </summary>
    /// <param name="pguidCmdGroup">命令组的 GUID</param>
    /// <param name="cCmds">命令数</param>
    /// <param name="prgCmds">数组指示命令调用方需要状态信息的 OLECMD 结构</param>
    /// <param name="pCmdText">由OLECMDTEXT返回的单个命令的状态信息</param>
    public int QueryStatus(ref Guid pguidCmdGroup, uint cCmds, OLECMD[] prgCmds, IntPtr pCmdText)
    {
        return _Next.QueryStatus(ref pguidCmdGroup, cCmds, prgCmds, pCmdText);
    }

    /// <summary>
    /// 确认完成或者丢弃
    /// </summary>
    private bool Complete(bool force)
    {
        if (_CurrentSession == null || !_CurrentSession.IsStarted)
            return false;

        //如果用户没有选择并且主动丢弃
        if (!_CurrentSession.SelectedCompletionSet.SelectionStatus.IsSelected && !force)
        {
            _CurrentSession.Dismiss();
            return false;
        }
        else
        {
            _CurrentSession.Commit();
            return true;
        }
    }
}