The onMouseDown( ) event handler is the callback form (and more modern analogue) of the legacy onClipEvent (mouseDown) event handler. The onMouseDown( ) event handler is identical to the Mouse.onMouseDown( ) listener event, except that it allows for screen refreshes between frames via updateAfterEvent( ). It executes when mc is on stage and the primary mouse button is depressed. The MovieClip.onMouseDown( ) handler would be obsolete in Flash 6 if Mouse.onMouseDown( ) supported updateAfterEvent( ). For complete details, see Mouse.onMouseDown( ).
Example
// Callback form _root.onMouseDown = function () { trace("The mouse was pressed"); } // Flash 5-style onClipEvent() block placed directly on a movie clip instance onClipEvent (mouseDown) { trace("The mouse was pressed"); }