You can use a constant of type ThemePopupArrowSize in the function DrawThemePopupArrow to specify the size of the pop-up arrow that is drawn on a button. The ThemePopupArrowSize constants are available with Appearance Manager 1.1 and later.
enum {
kThemeArrow3pt = 0,
kThemeArrow5pt = 1,
kThemeArrow7pt = 2,
kThemeArrow9pt = 3
};
typedef UInt16 ThemePopupArrowSize;