onRenderStart event: allow userland code to abort or otherwise replace the grid render process at will (by calling e.stopPropagation() / e.preventDefault()); one use case is where complex application logic may allow the render() timeslice while the grid is in a temporary flux, e.g. a complex data update with semi-invalid state during that update process. Then you don't want the render() timeslice to kick in and crash in userland custom formatters, etc., but instead you want the render to hold off until the other process has completed and things have stabilized again enough to warrant a grid (re)render.