Bug 184905

Summary:	Transforming an element into the viewport causes a miscalculated height until a reflow happens
Product:	WebKit	Reporter:	Jack Hanford <jackhanford>
Component:	Animations	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	dino, simon.fraser, webkit-bug-importer, zalan
Priority:	P2
Version:	Safari Technology Preview
Hardware:	All
OS:	macOS 10.13

Description Jack Hanford 2018-04-23 21:27:44 PDT

I've noticed a bug where in my webkit based browsers (latest webkit build, Safari on my mac (10.13) and iOS 11.3) .. after animating an element into the viewport via `translate3d`, sometimes the parent elements height/width aren't properly calculated until a reflow occurs. (Easy repro, is by resizing the viewport)

I'm able to reliably reproduce this issue on this URL: https://dist-okumnjynhx.now.sh 

I've also recorded a video to help demonstrate the bug: https://d.pr/v/WYTlbj

I can link to code if it's helpful, though I noticed it while building a react plugin, so there are few abstractions on top.

The environment above works as expected in both firefox and chrome.

Let me know if there is any additional information that would help debug!