Open Radar

 
Summary:
window.innerHeight reports an inaccurate value on page load when queried within a custom in-app browser - for example, Twitter for iOS (v6.43.1) and Facebook for iOS (v45.0).

Steps to Reproduce:
1. on the window's "load" event, query and log window.innerHeight
2. sometime after, re-query window.innerHeight

Expected Results:
window.innerHeight is accurate, does not change after "load" event

Actual Results:
window.innerHeight is inaccurate when "load" event fires, is accurate sometime after

Version:
iOS 9.2

Notes:
alternately, you can:

1. host the attached html file on a publicly accessible web server
2. share a link to said html file on twitter or facebook
3. view the shared link within twitter or facebook for iOS

tapping the "Calculate Dimensions" re-runs the viewport measurements. you'll see that on load "innerHeight" uses one value, then when dimensions are recalculated it uses another. the later value is accurate.

Configuration:
iPhone 6s

Attachments:
'viewport.html' was successfully uploaded.