TControl.ClientWidth
From OpenEUO
RW ClientWidth : n Specifies the horizontal size of the control's client area in pixels.
Use ClientWidth to read or change the width of the control’s client area. For TControl, ClientWidth is the same as Width. Derived classes may implement a ClientWidth property that differs from Width. For example, the ClientWidth of a form is the value of the Width property minus the width of the resize border and scroll bars.
