private bool TryInvokeSnippetCompletion(TabKeyCommandArgs args)
{
var subjectBuffer = args.SubjectBuffer;
var caretPoint = args.TextView.GetCaretPoint(subjectBuffer).Value.Position;
var text = subjectBuffer.AsTextContainer().CurrentText;
// If the user types "<line start><spaces><question><tab>"
// then the editor takes over and shows the normal *full* snippet picker UI.
// i.e. the picker with all the folders and snippet organization.
//
// However, if the user instead has something like
//
// "<line start><spaces><identifier><question><tab>"
//
// Then we take over and we show a completion list with all snippets in it
// in a flat list. This enables simple browsing and filtering of all items
// based on what the user typed so far.
//
// If we detect this pattern, then we delete the previous character (the
// question mark) and we don't send the tab through to the editor. In
// essence, the <quesiton><tab> acts as the trigger, and we act as if that
// text never makes it into the buffer.
if (!Workspace.TryGetWorkspace(subjectBuffer.AsTextContainer(), out var workspace))
{
return(false);
}
var documentId = workspace.GetDocumentIdInCurrentContext(subjectBuffer.AsTextContainer());
if (documentId == null)
{
return(false);
}
var document = workspace.CurrentSolution.GetDocument(documentId);
if (document == null)
{
return(false);
}
// There's was a buffer-Document mapping. We should be able
// to get a CompletionService.
var completionService = GetCompletionService();
Contract.ThrowIfNull(completionService, nameof(completionService));
var rules = completionService.GetRules();
if (rules.SnippetsRule != SnippetsRule.IncludeAfterTypingIdentifierQuestionTab)
{
return(false);
}
var syntaxFactsOpt = document.GetLanguageService <ISyntaxFactsService>();
if (syntaxFactsOpt == null ||
caretPoint < 2 ||
text[caretPoint - 1] != '?' ||
!CompletionSource.QuestionMarkIsPrecededByIdentifierAndWhitespace(text, caretPoint - 1, syntaxFactsOpt))
{
return(false);
}
// Because <question><tab> is actually a command to bring up snippets,
// we delete the last <question> that was typed.
var textChange = new TextChange(TextSpan.FromBounds(caretPoint - 1, caretPoint), string.Empty);
workspace.ApplyTextChanges(documentId, textChange, CancellationToken.None);
this.StartNewModelComputation(
completionService, new CompletionTrigger(CompletionTriggerKind.Snippets));
return(true);
}
