TPropertyPage = class(TCustomForm)
class PASCALIMPLEMENTATION TPropertyPage : public Vcl::Forms::TCustomForm
TPropertyPage is the base class for controls that represent an ActiveX control's property page.
TPropertyPage extends TCustomForm by adding the functionality needed to embed the form in an ActiveX property page dialog. It also adds methods to copy property values from the object to the form's controls, and vice versa.
To implement your own property page for an ActiveX object, derive a new class from TPropertyPage, design the form, then override the UpdateObject and UpdatePropertyPage methods. The IDE provides an expert for creating a skeleton property page. See Creating a new property page for more information.
TPropertyPage provides a helper method, Modified, that your form can call when any of the controls on the form are changed by the user. Calling the Modified method notifies the property dialog that the user has modified the object's properties. Normally this will enable the Apply button on the property dialog.