Can we hook custom handler on click of given bold, italic button /icon click in Google document through Google app scripts -

i found google app scripts cool extending many custom functionality. stuck in 1 case want show message on click of bold, italic buttons(icons) embedded in google document. able same thing custom menu items unable trap events raised given buttons/icons.is there api exposed in google apps scripts?

document-contained scripts have ability extend document editor ui functionality adding menus, sidebars , dialogs.

there no api access standard ui menus or buttons.