STR: - visit https://labs.jensimmons.com/2017/02-010.html - open the inspector, and select for example `.auto > div:nth-child(3)` - enable the flex highlighter - scroll the page down until `.none > div:nth-child(4)` ER: - the highlighter, incl. background pattern, should show up on the selected element AR: - parts of the highlighter show up somewhere else on the page The attached video shows another example.

This seems to be working fine since at least bug 1499630. We should retest once that bug lands.

@Martin Can you test this on the latest nightly?

Can still reproduce it on latest m-c.

Ironically, IT made me send my 4K screen back to them a month or two back because "I didn't need it." Now I am unable to reproduce the issue because I don't have a 4K screen. Anyhow, I think the cause is the canvas itself moving around... in this case whilst still drawing the highlight. Bug 1509071 should fix this.

Happens to me too on windows 10 with an external monitor (same as Martin's). Though it's not as bad as in Martin's video. For me the justify content area gets incorrectly placed by ~20px or so.

I noticed another thing about the misplaced pattern: it follows on horizontal scroll, while the outline does not. See video attached.

I can totally reproduce this without a big screen. This just happened to me on https://labs.jensimmons.com/2017/02-010.html, on my macBook 12'' laptop screen, on the element section.none > div.flex

Pushed by pbrosset@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/b89aa42e2fae take zoom and dpr into account when rendering justify-content; r=miker