pkg/lib: fix context menu component popdown

[allisonkarlitskaya]

f9b0166 changed the popdown behaviour of the context menu.

Before that commit, the previous code was wrong. It was:

 const wasOutside = !(event.target.contains === root.current);

 if (wasOutside)
     setVisible(false);

but because event.target.contains is a function, the comparison was always false and wasOutside would always be true. This meant that any left click would always pop the menu down.

The replacement code was:

const wasOutside = !event.target.contains(root.current);

which at least looks like it does something meaningful. Unfortunately this is also wrong, but in the other direction: this means that the menu will only pop down if it's not contained inside of the item you've clicked on. If you click on a large top-level

(ie: something which effectively contains "most things") then the menu will remain shown. That's definitely wrong.

We seemed to be happy with the behaviour before the original change, but the code has a purpose: it allows clicking on content of the menu (like on a divider, for example) without dismissing it. Let's try to implement the intended original behaviour: we should dismiss the menu only if the element that we clicked on is outside of the menu:

const wasOutside = root.current && !root.current.contains(event.target);

Fixes #20649

[martinpitt]

Thanks! I assume you interactively tested this, as we obviously don't cover this with tests.

[allisonkarlitskaya]

Ya, I did a fair amount of interactive testing to bisect the issue in the first place and then to decide what the correct behaviour ought to be, and I did test this result.

I'd probably need some help to develop a proper test case for this...