In the new commit r8667, the controls TVpDayView, TVpWeekView and TVpMonthView have a new event OnPrepareEventFont(Sender: TObject; AEvent: TVpEvent; AFont: TFont) which fires immediately before the event text is painted. In its handler, you can change font parameters depending on other parameter, e.g. on properties of AEvent. Note, however, that the size of the event rectangle already has been calculated, therefore it is not recommended to change the font size.