Returns the threshold for the gridline tooltips based on the mouse location.
Calculated based on the mouse position between the two closest gridlines or edges of chart.
Parameters
mousePos: any
Returns number
getOptions
getOptions():any
graphs used in combo charts share a model with global options but can receive their own local options.
this function retrieves the global options and merges it with any options passed into this
component's config.options object.
Returns the active gridlines based on the gridline threshold and mouse position.