Microsoft.R.Editor.Tree.TreeUpdateTask.ProcessComplexChange C# (CSharp) Method

        private void ProcessComplexChange(TextChangeContext context) {
            // Cancel background parse if it is running
            Cancel();

            TextChange textChange = new TextChange() {
                OldTextProvider = context.OldTextProvider,
                NewTextProvider = context.NewTextProvider
            };

            try {
                // Get write lock since there may be concurrent readers 
                // of the tree. Note that there are no concurrent writers 
                // since changes can only come from a background parser
                // and are always applied from the main thread.
               _editorTree.AcquireWriteLock();

                if (_pendingChanges.FullParseRequired) {
                    // When full parse is required, change is like replace the entire file
                    textChange.OldRange = TextRange.FromBounds(0, context.OldText.Length);
                    textChange.NewRange = TextRange.FromBounds(0, context.NewText.Length);

                    // Remove damaged elements if any and reflect text change.
                    // the tree remains usable outside of the damaged scope.
                    bool elementsChanged = _editorTree.InvalidateInRange(context.OldRange);
                    _editorTree.NotifyTextChange(context.NewStart, context.OldLength, context.NewLength);
                } else {
                    textChange.OldRange = context.OldRange;
                    textChange.NewRange = context.NewRange;

                    DeleteAndShiftElements(context);
                    Debug.Assert(_editorTree.AstRoot.Children.Count > 0);
                }

                _pendingChanges.Combine(textChange);
                _pendingChanges.Version = TextBuffer != null ? TextBuffer.CurrentSnapshot.Version.VersionNumber : 1;

                UpdateTreeTextSnapshot();
            } finally {
                // Lock must be released before firing events otherwise we may hang
                _editorTree.ReleaseWriteLock();
            }

            _editorTree.FireOnUpdateCompleted(TreeUpdateType.NodesRemoved);
        }