From RAD Studio API Documentation
typedef void __fastcall (__closure *TMouseMoveEvent)(System::TObject* Sender, System::Classes::TShiftState Shift, float X, float Y);
Procedural type that is used for all OnMouseMove event types.
A TMouseMoveEvent event handler must be called with the following parameters:
Sender--a pointer to the object that called this function.
Shift--indicates which shift keys--SHIFT, CTRL, ALT, and CMD (only for Mac)--were down when the user pressed the mouse button.
Y--the pixel coordinates of the mouse pointer within the client area of the control.