View source for TControl.ClientHeight

 RW ClientHeight : n
 
 Specifies the vertical size of the control's client area in pixels.

Use ClientHeight to read or change the height of the control’s client area. For TControl, ClientHeight is the same as Height. Derived classes may implement a ClientHeight property that differs from Height. For example, the ClientHeight of a form is the value of the Height property minus the height of the resize border and scroll bars.