Bug 242020

Summary: Fixed background-attachment on scrolling element misbehaving.
Product: WebKit Reporter: omimanav
Component: Layout and RenderingAssignee: Nobody <webkit-unassigned>
Status: NEW    
Severity: Major CC: bfulgham, omimanav, simon.fraser, webkit-bug-importer, zalan
Priority: P2 Keywords: InRadar
Version: Other   
Hardware: All   
OS: All   
Attachments:
Description Flags
Video with code, demonstrating the issue, notice the laggy/glitchy behaviour.
none
Test case none

omimanav
Reported 2022-06-26 22:34:16 PDT
Created attachment 460500 [details] Video with code, demonstrating the issue, notice the laggy/glitchy behaviour. See video attached; as if a fixed background on a scrolling body has a hard time rendering on scroll instead of being a fixed background. I've included the test code below. This isn't an issue on any other browser. Browser in video is Gnome Web (latest version as of 27/7/22 on Ubuntu repository). The body is the scrolling element and the background of it tries to keep up with scrolling instead of remaining static/fixed. Example code shown in video to demonstrate the issue: <head> <style> div { height: 450vh; width: 100vw; padding: 0; margin: 0; } body { background: url("https://i.ibb.co/4FXCrmS/1651208527285.gif"); background-attachment: fixed; background-repeat: no-repeat; background-size: cover; } </style> </head> <body> <div>Test div block</div> </body> ```
Attachments
Video with code, demonstrating the issue, notice the laggy/glitchy behaviour. (4.17 MB, video/webm)
2022-06-26 22:34 PDT, omimanav 		no flags
Details
Test case (763 bytes, text/html)
2022-06-27 11:42 PDT, Simon Fraser (smfr) 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
omimanav
Comment 1 2022-06-27 11:37:03 PDT
It's an issue on macOS 10.15 Safari (don't recall what version) and misbehaving albeit differently to this on iOS 15 (doesn't behave as "fixed" attachment). Please consider leaving this an issue on all platforms not just Linux.
Simon Fraser (smfr)
Comment 2 2022-06-27 11:42:12 PDT
I don't see any performance issues on macOS, and on iOS `background-attachment: fixed;` is not supported.
Simon Fraser (smfr)
Comment 3 2022-06-27 11:42:29 PDT
Created attachment 460503 [details] Test case
Radar WebKit Bug Importer
Comment 4 2022-07-03 22:35:13 PDT
<rdar://problem/96380216>
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