Created attachment 387254 [details] Screenshot of Twitter on my iPad showing the line at the top of the site. Hi. I'm a web engineer on twitter.com. I have found an infrequent rendering bug when using iPhone or iPad with mobile.twitter.com. I use dark mode on the OS and on twitter. I scroll my home timeline. When scrolling stops, I sometimes see one pixel of rendering from the timeline under the top header, appearing above the header. This is most apparent when there is a bright image in the timeline. This bug either does not appear, or is much less apparent, when the phone is not in dark mode. I suspect it is less apparent. I have made a reduced test case here: https://clumsy-biplane.glitch.me (make sure your phone is in dark mode) The bug appears far less frequently in the reduced test case. Perhaps 20-30 scrolls up and down might be needed. I find the line only appears after the scroll moment has finished. By comparing screenshots, I believe the line is an additional line, because I measured an extra 1px between the top of the screen and the text in the header.
Probably a rounding error in the positioning of the position:fixed header. Does the patch have a meta viewport that gives it unit scale (width=device-width)?
Yes, reduced test case has <meta name="viewport" content="width=device-width, initial-scale=1"> Site has <meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=0,viewport-fit=cover" />
<rdar://problem/58471889>
@Kenneth, Spring Cleaning. I don't seem to be able to reproduce this issue.