What (if anything) is broken and where? In particular we should review real old iOS devices to check the experiences there.

Nothing seems broken. We can safely remove the code. Compare these screencasts:

1. iOS 3 / iPhone 3GS

a) Listening to Skin's scroll event:

b) Listening to MobileFrontend's scroll event (i.e. window.scroll):

2. IE 9 / Windows 7

a) Listening to Skin's scroll event:

b) Listening to MobileFrontend's scroll event (i.e. window.scroll):

Besides, changing of the window's height happens for all matching browsers but the value is only amended for old iOS device.

And lastly, these changes may have been developed with mobile editing in mind, but mobile editing is disabled on these browsers (A toast message shows up when the user clicks on the edit icon.)

Should we remove supportsPositionFixed and Skin#setupPositionFixedEmulation or fix them?

Remove. We can close T143337 and work on T144558.

Remove. We can close T143337 and work on T144558.

👍

@Jdlrobson, @Jhernandez, @jhobs: It'd be good if someone else could weigh in.

Sounds good @bmansurov but I'd recommend someone with a real ios device (the older the better) gives this a quick sanity check given emulators and real devices can have a different behaviour. Who in the team has one?

Nice. My oldest ones are ipad 2 and iphone 4 with ios 9, so may not qualify...

Let's see if somebody else can confirm

Given the special casing of <textarea> and <input> elements in Skin#setupPositionFixedEmulation, I tested searching and editing on a physical iPod Touch running iOS 6.1.6 (10B500) on our staging server. Before I started the test I made sure that the server was up to date by running the following:

ssh reading-web-staging-3
cd /srv/mediawiki-vagrant
vagrant git-update

Both features worked as expected – I was able to edit a page without issue.

I just checked references on iOS 3 on IPhone 3GS with and without removing the code as suggested. In both cases references are broken and don't stick to the bottom of the page.