Replace unload with visibility API

[georeith]

Description

In chrome when clicking on a link that has headers of Content-Disposition: Attachment it triggers a file download, if that URL is on an external URL and you can't use the download attribute (which only works on same origin) then it also fires the unload event on window, despite not actually unloading the page.

HocuspocusProvider listens to unload and clears out the awareness state, there is then no follow up event to reinstate it:

hocuspocus/packages/provider/src/HocuspocusProvider.ts

Line 282 in d5cf421

window.addEventListener('beforeunload', this.boundBeforeUnload)

Instead we should use the Page Visibility API to clear out awareness (which will work on tabbing in and out also) but also does not trigger when clicking on downloads in Chrome.

Whilst this is partly a quirk of the browser there is a somewhat simple workaround.

Steps to reproduce the bug

1. Click on a link to an external file with the header Content-Disposition: Attachment
2. See that your awareness state is emptied despite not leaving the page
3. Awareness will not recover despite still being connected to the server

Expected behavior

Awareness should not get cleared when clicking on links that don't leave the page.

Screenshot, video, or GIF

Screen.Recording.2023-07-21.at.17.16.52.mov

Environment?

• operating system: MacOS 13
• browser: Chrome 114
• Hocuspocus version: 2.3.0

[georeith]

Actually this issue is fixed by: #658

[janthurau]

😎 closing this - let me know if is is really fixed in 2.3.0 :-)