TControl.OnMouseWheelUp

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

Declaration

Source position: controls.pp line 1604

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