Cache mousemove and hook keyboard to allow scanning at mouse position while mouse is no longer moving

[Kuuuube]

Fixes #533

Something worth noting here is how the following interations work:

Interaction 1:

move mouse -> stop mouse -> scan -> close popup -> move mouse -> stop mouse -> scan

This works totally fine. Both times the user presses the button to scan they will get the popup and the word will be scanned.

Interaction 2:

move mouse -> stop mouse -> scan -> move mouse (first popup is not closed) -> stop mouse -> scan

This does not work. The user will get the first popup but then the second popup won't show (unless the user was scanning a word inside the first popup). This is because the user's browser will have focused inside the popup window and all event listeners outside of it can no longer access the keypresses.

On a normal webpage this wouldn't be an issue but Yomitan popups actually aren't even the same webpage. And a browser will not allow a webpage to access keystrokes being sent inside a different webpage. This behavior applies regardless of whether Yomitan is using a secure container and url or not.

Now this may raise the question of why moving the mouse before scanning while a different popup is open allows scanning with no problems. This is because modifier data can be accessed through mouse events and the browser will let those through since the mouse is hovering over the parent webpage with the event listener in it and not the popup's separate webpage.

misclick

[phly95]

How do you bind a key to scan without moving the mouse?