207256 2020-02-05 04:20:05 -0800 visibilitychange event does not get always fired on background but it may on foreground 2020-07-13 16:13:45 -0700 1 1 1 Unclassified WebKit WebCore JavaScript Safari 12 iPhone / iPad iOS 12 NEW https://bugs.webkit.org/show_bug.cgi?id=205942 InRadar P2 Normal --- 1 cerutti.alexander webkit-unassigned cdumez Kongpheng.Nanthavongsa webkit-bug-importer oldest_to_newest 1614999 0 cerutti.alexander 2020-02-05 04:20:05 -0800 Hello, this is my first bug here and I'm not too sure about the information I filled to report this problem, since I'm not that into Webkit. What I experienced is that I've tried to attach a `visibilitychange` listener on my application. It contains a `console.log` and some logics that depend on `document.hidden`. So, if home button or sleep button is pressed, the event is fired and we can see in the debugging console the log. I've been reported, and I've verified, that sometimes this event is not fired when, for sure on iPad (also iOS 13), one of those two buttons are pressed. Instead the event is fired when Safari goes back in foreground. So the log gets printed twice. Moreover, sometimes `document.hidden` is `false` in both events. So if some logic is based on a check on that property, wrong code block may be run. I wasn't able to find a steady way to reproduce this, and this seems to happen in different cases. For example, I'm developing a video player (here is where the event is created). We are importing a third-party video AD engine. What we experienced is that during some ADs, on home/sleep buttons, the event is not fired on background but twice on foreground. This happened also during other video contents playback, but I'm not sure it is related to multimedia contents playback but instead on the amount of work the engine that is has to do when the buttons get pressed or some kind of concurrency problem on Safari background (but these are only thoughts of mine). If I'll ever find more details I'll edit or add a comment to increase the details. I hope this bug report is good enough (but I think this won't be) to find the problem. Thank you. 1615085 1 389818 cerutti.alexander 2020-02-05 09:43:03 -0800 Created attachment 389818 Repro html page 1615086 2 cerutti.alexander 2020-02-05 09:43:11 -0800 I've found a way to reproduce almost-steadly the problem while using sleep button. With the sample that I'm attaching, which is a normal video tag with a `visibilitychange` event attached on document, I've tried to lock and unlock the iPad with iOS 12, different times. The video was playing before this happened. Some unlocks (may vary from 3 to 5 or more), the video didn't came back to playing automatically and the `visibilitychanged` event started being fired only on foreground. This situation can persist for some other lock-unlock actions but it will recover somehow and then can fall back in this again. I don't know how this can be related or linked under the hood, but seems the only almost-steady way I found to reproduce this problem. Instead, I didn't found yet a way to reproduce the problem that happens when home button is pressed. Anyway, if the player is paused after unlock, pressing home button still fires the event `visibilitychanged`. I think that they might be two different but related problems. 1615552 3 webkit-bug-importer 2020-02-05 23:28:51 -0800 <rdar://problem/59215749> 1657505 4 cdumez 2020-05-29 16:29:54 -0700 Likely related to process suspension on iOS. When you lock the screen or home out of Safari, our processes get suspended shortly after. As a result, we may or may not have time to fire the visibilitychange event before we get suspended. The event normally gets fired when the process resumes if it did to have time to get fired before suspension. 1671216 5 Kongpheng.Nanthavongsa 2020-07-13 16:13:45 -0700 Any updates? This bug is still reproducible on iOS 13.5.1. I included a fiddle to reproduce the issue, without the need for a video element: https://jsfiddle.net/vkpheng/pv0omfrn/. To reproduce: * On iOS Safari, open this fiddle and run it * Click Home button to background Safari * Immediately click Safari icon to bring Safari back to the foreground * Notice that no alert pops up Expected: an alert pops up, since there was a visibility change. Please advise. Thanks! 389818 2020-02-05 09:43:03 -0800 2020-02-05 09:43:03 -0800 Repro html page index.html text/html 1487 cerutti.alexander PCFET0NUWVBFIGh0bWw+CjxodG1sIGxhbmc9ImVuIj4KPGhlYWQ+Cgk8bWV0YSBjaGFyc2V0PSJV VEYtOCI+Cgk8bWV0YSBuYW1lPSJ2aWV3cG9ydCIgY29udGVudD0id2lkdGg9ZGV2aWNlLXdpZHRo LCBpbml0aWFsLXNjYWxlPTEuMCI+Cgk8bWV0YSBodHRwLWVxdWl2PSJYLVVBLUNvbXBhdGlibGUi IGNvbnRlbnQ9ImllPWVkZ2UiPgoJPHRpdGxlPlZpc2liaWxpdHkgY2hhbmdlIHJlcHJvIG9uIHdl YmtpdDwvdGl0bGU+CgoJPHN0eWxlPgoJCXZpZGVvIHsKCQkJd2lkdGg6IDUwMHB4OwoJCX0KCTwv c3R5bGU+CjwvaGVhZD4KPGJvZHk+Cgk8dmlkZW8gc3JjPSJodHRwOi8vY29tbW9uZGF0YXN0b3Jh Z2UuZ29vZ2xlYXBpcy5jb20vZ3R2LXZpZGVvcy1idWNrZXQvc2FtcGxlL0JpZ0J1Y2tCdW5ueS5t cDQiIGNvbnRyb2xzPjwvdmlkZW8+Cgk8c2NyaXB0IHR5cGU9InRleHQvamF2YXNjcmlwdCI+CgkJ Y29uc3QgdmlkZW9UYWcgPSBkb2N1bWVudC5nZXRFbGVtZW50c0J5VGFnTmFtZSgidmlkZW8iKVsw XTsKCQl2aWRlb1RhZy5tdXRlZCA9IHRydWU7CgkJdmlkZW9UYWcudm9sdW1lID0gMDsKCgkJY29u c29sZS5sb2coIlN0YXR1czoiKTsKCQljb25zb2xlLmxvZygiSGFzIHN1cHBvcnQgZm9yICdvbnZp c2liaWxpdHljaGFuZ2UnIiwgIm9udmlzaWJpbGl0eWNoYW5nZSIgaW4gZG9jdW1lbnQpOwoKCQlj b25zdCB2aXNpYmlsaXR5RXZlbnRXaXRoUHJlZml4ID0gKAoJCQkoZG9jdW1lbnQuaGlkZGVuICE9 PSB1bmRlZmluZWQgJiYgInZpc2liaWxpdHljaGFuZ2UiKSB8fAoJCQkoZG9jdW1lbnQubXNIaWRk ZW4gIT09IHVuZGVmaW5lZCAmJiAibXN2aXNpYmlsaXR5Y2hhbmdlIikgfHwKCQkJKGRvY3VtZW50 LndlYmtpdEhpZGRlbiAhPT0gdW5kZWZpbmVkICYmICJ3ZWJraXR2aXNpYmlsaXR5Y2hhbmdlIikK CQkpOwoKCQljb25zdCBoaWRkZW5XaXRoUHJlZml4ID0gKAoJCQkoZG9jdW1lbnQuaGlkZGVuICE9 PSB1bmRlZmluZWQgJiYgImhpZGRlbiIpIHx8CgkJCShkb2N1bWVudC5tc0hpZGRlbiAhPT0gdW5k ZWZpbmVkICYmICJtc0hpZGRlbiIpIHx8CgkJCShkb2N1bWVudC53ZWJraXRIaWRkZW4gIT09IHVu ZGVmaW5lZCAmJiAid2Via2l0SGlkZGVuIikKCQkpOwoKCQljb25zb2xlLmxvZygiQ2hvc2VuIGV2 ZW50OiIsIHZpc2liaWxpdHlFdmVudFdpdGhQcmVmaXgsIGhpZGRlbldpdGhQcmVmaXgpOwoKCQlk b2N1bWVudC5hZGRFdmVudExpc3RlbmVyKHZpc2liaWxpdHlFdmVudFdpdGhQcmVmaXgsICgpID0+ IHsKCQkJY29uc29sZS5sb2coYCR7dmlzaWJpbGl0eUV2ZW50V2l0aFByZWZpeH0gaGFzIGJlZW4g Y2FsbGVkIG5vdyAoJHtEYXRlLm5vdygpfSkuIEhpZGRlbjpgLCBkb2N1bWVudFtoaWRkZW5XaXRo UHJlZml4XSk7CgkJCWNvbnNvbGUubG9nKCItLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0t LS0tLS0tIikKCQl9KTsKCgkJdmlkZW9UYWcucGxheSgpOwoJPC9zY3JpcHQ+CjwvYm9keT4KPC9o dG1sPgo=