Determines whether this contribution can handle the split operation for the given widget.
the widget to check
a priority number (higher means higher priority), or 0 if this contribution cannot handle the widget
Splits the given widget according to the specified split mode.
the widget to split
the direction in which to split
the newly created widget, or undefined if the split operation failed
Implementation of SplitEditorContribution for notebook editors (NotebookEditorWidget). Delegates to NotebookOpenHandler.openToSide which handles counter management for splits.