Restricting user interaction while a certain process is running

MIT App Inventor Help
1

I have the following situation.
On a press of a button a canvas needs to be redrawn (practically bit by bit), and it takes a long time. I would like to pause registering user interaction while this process is running.
My idea is the following. Instead of using the button.clicked event, I use the button.touchdown event to disable all buttons (and other parts that can have user interaction) and then do the long calculation followed by enabling the buttons in the button.touchup event.
My question is the following.
As far as I know, user interactions can be registered while other processes are running, but can responses to user interactions run parallel to each other, or in any particular time only one of these are running? In particular, can I be sure that the start of the touchup script will be after the end of the touchdown script?

2

See

for some essays on the AI2 event model.