procedure Invalidate; override;
virtual void __fastcall Invalidate();
Schedules a control repaint.
Invalidate informs a control that its entire surface needs to be repainted. Calling Invalidate can prevent flicker caused by a series of partial repaints. There is no performance penalty for calling Invalidate multiple times before the control is actually repainted.
The actual repaint does not occur until the control is updated. To force an immediate repaint, call Repaint instead.