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

# TControl.OnMouseWheelHorz

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

## Declaration

Source position: controls.pp line 1597

`protected property TControl.OnMouseWheelHorz : TMouseWheelEvent read FOnMouseWheelHorz write FOnMouseWheelHorz;`

## Description

OnMouseWheelHorz is a TMouseWheelEvent property with the event handler signalled when a mouse wheel tilt event occurs in the control. It is signalled (when assigned) from the DoMouseWheelHorz method, and occurs when the LM_MOUSEHWHEEL message is handled in the WMMouseHWheel method.

An application can implement and assign a TMouseWheelEvent routine to the event handler to perform actions needed when the event occurs in the control. Other control handlers, created using AddHandler and the chtOnMouseWheelHorz handler type, may be signalled if OnMouseWheelHorz has not been assigned or does not handle the mouse wheel event.

OnMouseWheelLeft or OnMouseWheelRight may be signalled (when assigned) if OnMouseWheelHorz or other control handlers have not been assigned or do not handle the mouse wheel event. The value in the WheelDelta argument determines which handler is used; OnMouseWheelLeft when the delta is a negative number and OnMouseWheelRight when the delta is 0 or a positive number.

OnMouseWheelHorz, and the other horizontal mouse wheel event handlers, require a mouse with a tilting scroll wheel to generate the event notification.

## See also

TControl.OnMouseWheelLeft |  | Event handler signalled for a leftward movement of the mouse wheel.
TControl.OnMouseWheelRight |  | Event handler signalled for a rightward movement of the mouse wheel.
TControl.OnMouseWheel |  | Event handler for mouse wheel turned.
TControl.AddHandler |  | Adds a notification handler for the specified control handler type.
TMouseWheelEvent |  | Specifies an event handler used to respond to mouse wheel events.
TControlHandlerType |  | Notification handler types.