TCustomDockForm = class(TCustomForm)
class PASCALIMPLEMENTATION TCustomDockForm : public TCustomForm
TCustomDockForm is the default floating dock site class for TControl objects.
When a control is created, TCustomDockForm is the type assigned to its FloatingDockSiteClass property. You can use TCustomDockForm as the basis for your own floating dock site class, and then assign the new class to the a control's FloatingDockSiteClass property.