MQL5 ReferenceStandard LibraryPanels and DialogsCScrollOnThumbDragStart CreateOnEventMinPosMaxPosCurrPosCreateBackCreateIncCreateDecCreateThumbOnClickIncOnClickDecOnShowOnHideOnChangePosOnThumbDragStartOnThumbDragProcessOnThumbDragEndCalcPos OnThumbDragStart The virtual handler of the control "ThumbDragStart" (drag start) event. virtual bool OnThumbDragStart() Return Value true - event processed, otherwise - false. Note The "ThumbDragStart" event occurs at start of the drag operation. OnChangePos OnThumbDragProcess