Thank you for your answers.
So basically the control hold a pointer to main ChStyle class for his style or a pointer to another ChStyle if main style get replaced for that control (only) with another style?
Buttons use the same small image (12x22) and the resizing algorithm is called every time the control Paint is called? Isn't used a cache to store new resized image for a control so not having to resize a small image every time when Paint is called?