In your case the mouse button event is not being passed on. Would it work to send a mouse event when the button event occurs?
Code:
import viz
viz.go()
import vizinfo
infoObject = vizinfo.add('Give me feedback!')
button = infoObject.add(viz.BUTTON, 'Push me')
def onMouse():
pos = viz.mouse.getPosition()
print 'mouse is currently at',pos
vizact.onmousedown(viz.MOUSEBUTTON_LEFT, onMouse)
def onButton(obj,state):
if state == viz.ON:
viz.sendEvent( viz.MOUSEDOWN_EVENT, viz.MOUSEBUTTON_LEFT )
viz.callback(viz.BUTTON_EVENT,onButton)