Bug 205792 – macOS fullscreen mode breaks user interaction in HTML5 Fullscreen with external display

• Status: RESOLVED
• Resolution: CONFIGURATION CHANGED
• Component: UI Events

[Jeremy Karlsson]

If you are on a page that supports HTML5 fullscreen and go into fullscreen the web app works if Safari is in windowed mode, but if the user has pressed the green button on the top left in the macOS GUI to make the app fullscreened in the OS before enter HTML5 Fullscreen, then any user input in the web app stops working.

Isolated test case: https://cdpn.io/enjikaka/debug/jOEYGQW/gaAeYzgXbooA

This can be reproduced on TIDAL and YouTube. And probably anywhere else that uses HTML5 Fullscreen API too.

[Radar WebKit Bug Importer]

<rdar://problem/58365418>

[Antoine Quint]

Hi Jeremy, sadly the link you provided doesn't work. Could you provide an updated test case?

[Antoine Quint]

I also don't see the problem reproducing with YouTube, but I might not run the steps correctly. Here's what I did:

1. Open YouTube.com and navigate to a video
2. Make Safari fullscreen by clicking the green button in the application menu bar
3. Enter fullscreen by clicking on the fullscreen icon in the YouTube player bar
4. Left fullscreen by clicking on the fullscreen icon in the YouTube player bar
5. Made Safari no longer fullscreen by clicking on the green button in the application menu bar

If you can provide steps to reproduce with YouTube that'd be great. A screen recording can also be useful.

Until then, filing this bug as RESOLVED/WORKSFORME as we don't have enough actionable information as it stands.

[Jeremy Karlsson]

Change the /debug/ part in the URL to /full/ and it should work.

After step 3, try using the player controls in the youtube player. That does not work.

[Jeremy Karlsson]

Created attachment 387090 [details]
Recording of error

Observe how mouse events are ignored on 0:30. Can only exit fullscreen with ESC here and not use the player at all.

[Jeremy Karlsson]

*reopening*

[Antoine Quint]

I'm not reproducing the issue you show in the screen recording in Safari with macOS 10.15.2, nor can I reproduce with your test. Does it reproduce with a Safari Technology Preview build?

[Jeremy Karlsson]

I'll test the Technology Preview build!

The exact version of Safari installed is; 13.0.4 (15608.4.9.1.3).

External monitor usage on macOS is sadly very very buggy, and it actually looks like that might be part of the issue here. I'm using a monitor through the USB-C  port with my MacBook Pro folded, so I only have output on the external monitor. When in this mode I can consitently reproduce the issue on all pages using the Fullscreen API.

I can not reproduce this is if I just use the internal screen on the MacBook Pro. If I connect the external monitor again though I can reproduce.

If I unfold the MacBook so that both the internal montitor and the external montior is running, then I can also not reproduce. 

Peculiar... With Chrome or Firefox in "macOS fullscreen" with HTML5 Fullscreen I cannot reproduce, it only happens with Safari. So must be some calculations that are off so that the mouse position isn't correctly matched to the rendered page?

[Antoine Quint]

Thanks for this information Jeremy, this does sound like an issue with external monitors.