[Overview][Constants][Types][Classes][Procedures and functions][Variables][Index] | Reference for unit 'Controls' (#lcl)

# TControl.OnMouseWheelDown

Event handler signalled for a downward movement of the mouse wheel.

## Declaration

Source position: controls.pp line 1595

`protected property TControl.OnMouseWheelDown : TMouseWheelUpDownEvent read FOnMouseWheelDown write FOnMouseWheelDown;`

## Description

OnMouseWheelDown is a TMouseWheelUpDownEvent property with the event handler signalled when a downward movement of the mouse wheel has occurred in the control.

OnMouseWheelDown is signalled (when assigned) from the DoMouseWheelDown method using the control instance as the Sender for the event notification. It occurs when the OnMouseWheel event handler has not been assigned, or does not handle the mouse wheel event.

Use OnMouseWheelUp to perform actions needed when an upward movement of the mouse wheel has occurred.

Use OnMouseWheel when a delta value with the direction for the mouse wheel movement is needed.

## See also

TControl.OnMouseWheel |  | Event handler for mouse wheel turned.
TControl.OnMouseWheelUp |  | Event handler signalled for an upward movement of the mouse wheel.
TControl.DoMouseWheelDown |  | Signals the OnMouseWheelDown handler.
TControl.DoMouseWheel |  | Signals the OnMouseWheel handlers, when the mouse wheel has been turned.
TMouseWheelUpDownEvent |  | Type of OnMouseWheelUp/Down event handlers.