TUIControl that has a position and takes some rectangular space on the container.
The position is controlled using the Left, Bottom fields. The rectangle where the control is visible can be queried using the Rect virtual method.
Note that each descendant has it's own definition of the size of the control. E.g. some descendants may automatically calculate the size (based on text or images or such placed within the control). Some descendants may allow to control the size explicitly using fields like Width, Height, FullSize. Some descendants may allow both approaches, switchable by property like TCastleButton.AutoSize or TCastleImageControl.Stretch.
Position and size of this control, assuming it exists. This must ignore the current value of the GetExists method and Exists property, that is: the result of this function assumes that control does exist.