Klappt doch. Setze mal einen Breakpoint in TCustomTabControl.DrawTab von ComCtrls in die Zeile "IF Assigned(FOnDrawTab)".
Delphi-Quellcode:
PROCEDURE TShellForm.PageControlDrawTab(control:TCustomTabControl; tab_index:Integer; CONST rect:TRect; active:Boolean);
BEGIN
WITH PageControl
DO Canvas.TextOut(rect.Left+5,6,Pages[tab_index].Caption)
END; {OF PROCEDURE TShellForm.PageControlDrawTab}