onEmphasis = function () {
	                        circle.setStyle({
	                            text: hoverLabelModel.get('show') ? labelText : '',
	                            textFill: hoverTextStyleModel.getTextColor(),
	                            textFont: hoverTextStyleModel.getFont()
	                        });
	                    }
This flag is used to make sure that only one among
`pan`, `zoom`, `click` can occurs, otherwise 'selected'
action may be triggered when `pan`, which is unexpected.
@type {booelan}