Hi wp, thanks for your response.
My specific issue is that I have created a TDesignMediator which takes care of drawing the controls and components owned by my "form" (not exactly a TForm descendant, though).
All controls are painted correcly by my own code. However I'd like it to paint the other components (e.g. a TDataSource) exactly as TDesigner does. TDesigner contains a method to draw non visible components, but I can't call it directly.
Unfortunately the TDesignMediator doesn't seem to have means to let the designer know that it should paint the component as usual, or I missed something?