How to use the flexx.event.reaction function in flexx

    @event.reaction('buttons.children*.pointer_down')
    def run_test(self, *events):
        global window, perf_counter
        self.status.set_text('Test results: ')
        self.progress.set_value(0)

        tests = []
        for ev in events:
            if isinstance(ev.source, ui.Button):
                sze = 5 if '5' in ev.source.text else 1
                n = int(ev.source.text.split(' ')[0])
                for i in range(n):
                    tests.append(sze)

        self.progress.set_max(len(tests))
        self._start_time = perf_counter()
        for n in tests:

    @event.reaction('disabled')
    def __disabled_changed(self, *events):
        if events[-1].new_value:
            self.node.setAttribute("disabled", "disabled")
        else:
            self.node.removeAttribute("disabled")

    @event.reaction('key_down')
    def __on_key(self, *events):
        for ev in events:
            value = self.value
            if ev.key == 'Escape':
                self.outernode.blur()
                self.user_done()
            elif ev.key == 'ArrowRight':
                if isinstance(value, float):
                    self.user_value(value + self.step)
                else:
                    self.user_value([v + self.step for v in value])
            elif ev.key == 'ArrowLeft':
                if isinstance(value, float):
                    self.user_value(value - self.step)
                else:
                    self.user_value([v - self.step for v in value])

    @event.reaction('!bar')
    def on_bar(self, *events):
        print('bar reaction called with %i events' % len(events))

    @event.reaction
    def _update_minmaxsize(self):
        """ Update the internal _size_limits.
        Note that this is an implicit reaction.
        """
        # Get new limits
        w1, w2, h1, h2 = self._query_min_max_size()
        w1 = max(0, w1)
        h1 = max(0, h1)
        # Update the property, so that our parent may react
        self._set_size_limits((w1, w2, h1, h2))
        # Update the style, so that flexbox works
        s = self.outernode.style
        s['min-width'] = w1 + 'px'
        s['max-width'] = w2 + 'px'
        s['min-height'] = h1 + 'px'
        s['max-height'] = h2 + 'px'

    @event.reaction('!eat')
    def track_eating(self, *events):
        for ev in events:
            print(ev.name + ' is eating')

    @event.reaction('!children**.pointer_click', '!children**.pointer_double_click')
    def _handle_item_clicked(self, *events):
        self._last_highlighted_hint = events[-1].source.id
        if self._highlight_on:  # highhlight tracks clicks
            self.highlight_show_item(events[-1].source)

        if self.max_selected == 0:
            # No selection allowed
            pass

        elif self.max_selected < 0:
            # Select/deselect any, but only with CTRL and SHIFT
            for ev in events:
                item = ev.source
                modifiers = ev.modifiers if ev.modifiers else []
                if 'Shift' in modifiers:  # Ctrl can also be in modifiers
                    # Select everything between last selected and current

    @event.reaction
    def __update_tabindex(self, *events):
        # Note that this also makes the widget able to get focus, and thus
        # able to do key events.
        ti = self.tabindex
        if ti < -1:
            self.node.removeAttribute('tabIndex')
        else:
            self.node.tabIndex = ti

    @event.reaction('foo')
    def react_to_foo_b(self, *events):
        # This function
        print('B: foo changed from %i to %i' % (events[0].old_value,
                                                events[-1].new_value))