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

# TControl.OnMouseWheelUp

Event handler signalled for an upward movement of the mouse wheel.

## Declaration

Source position: controls.pp line 1596

`protected property TControl.OnMouseWheelUp : TMouseWheelUpDownEvent read FOnMouseWheelUp write FOnMouseWheelUp;`

## Description

OnMouseWheelUp is a TMouseWheelUpDownEvent property with the event handler signalled when the mouse wheel has been rotated in the upward direction. It is signalled (when assigned) in the DoMouseWheelUp method.

OnMouseWheelUp occurs when a mouse wheel event is handled in the WMMouseWheel method, and an OnMouseWheel event handler has not been assigned or does not handle the mouse wheel event in the DoMouseWheel method.

The arguments for the TMouseWheelUpDownEvent event handler include:

Sender
  The control for the event notification.
Shift
  The Ctrl, Alt, or Shift modifier in effect when the wheel event occurred.
MousePos
  The location of the mouse pointer when the event occurred.
Handled
  An variable Boolean argument which indicates if the event is handled in the routine.

OnMouseWheelUp is used when the delta value (or the relative number of units of movement) is 0 (zero) or a positive number.

OnMouseWheelDown is used when the delta value is a negative number.

Neither OnMouseWheelUp nor OnMouseWheelDown include the delta value; they are simple notifications that the event has occurred at a given position.

Use OnMouseWheel when the delta value (or the relative number of units of movement) are important.

## See also

TControl.OnMouseWheel |  | Event handler for mouse wheel turned.
TControl.OnMouseWheelDown |  | Event handler signalled for a downward movement of the mouse wheel.
TControl.DoMouseWheel |  | Signals the OnMouseWheel handlers, when the mouse wheel has been turned.
TControl.DoMouseWheelUp |  | Signals the OnMouseWheelUp handler.
TControl.WMMouseWheel |  | Handles mouse wheel messages for the control.
TMouseWheelUpDownEvent |  | Type of OnMouseWheelUp/Down event handlers.