typedef void __fastcall (__closure *TGrpButtonDrawEvent)(System::TObject* Sender, int Index, Vcl::Graphics::TCanvas* Canvas, const System::Types::TRect &Rect, Vcl::Categorybuttons::TButtonDrawState State);
TGrpButtonDrawEvent is the type of Button Group draw event handler.
Each of these events is invoked once per button in the button group.
Sender is a reference to the TButtonGroup invoking the event.
Index is the index of the button in the button group.
Canvas is the canvas on which the drawing takes place.
Rect defines the rectangle in which the user drawing must be made.
State defines state of the button to be drawn.