ui.bang should flash only a short amount of time (maybe could be specified like classic bang?), so the object's ui behavior make the visual closer to data behavior, and a bit different from ui.button.
old behavoir: [ui.bang] is on on mouse-down, and off on mouse-up
new behavoir: [ui.bang] is on on mouse-down and off after 100ms or mouse-up, which one is earlier
ui.bang should flash only a short amount of time (maybe could be specified like classic bang?), so the object's ui behavior make the visual closer to data behavior, and a bit different from ui.button.