Comment by thyristan

Well, kind of.

Actually, the developer should really do some work in the UI thread beyond just sending out a "button pressed" message: When I press the button, I need immediate feedback that it was pressed and that pressing it had an effect, that things are now happening. Too many UIs, especially in the web where round-trip-times can be long, rely on just firing of a message or a network request. The response to the user, by displaying a spinner, progress bar, modal or new page only happens asynchronously and after a comparatively long delay. This means that users will sometimes repeatedly click because "nothing happens", leading to multiple messages, leading to multiple actions, leading to a big mess.

So the UI thread should synchronously trigger user feedback, take a lock or other measures to prevent unintended repeated actions and start a timeout callback in case the triggered action doesn't happen in a sensible timeframe.