Your wife has got it almost exactly right.

Yes, it is an automatic sunshade.

One tiny detail is still not right. I will not prolong this bounty. It was enough so I declare that ...

@fullcoverbetting's wife is a winner :)

And the answer is ...

The shade automatically rolls in when it detects that the rain is falling.

Since it was quite a storm a pool of water already accumulated on the shade. When the canopy rolled all the way in this water obviously had someplace to go. So it dropped down like a waterfall :)

The owner warned us that this will happen so we were able to escape the watefall :)