Twenty Seventeen Parallax Effect - Not Working Correctly on iOS

[bamboozle]

Theme: Twenty Seventeen
Version: 1.4 (latest at time of bug report)

The bug
When viewing the home page of this theme only the header image has the parallax effect on iOS. The featured images (further down the page) do not. I have tried it only on an iPad Pro 9.7 inch.

All images are displayed correctly (with the parallax effect) on Windows/Chrome.

I have been advised to create a bug report after first reporting the problem here:

​https://wordpress.org/support/topic/parallax-ios-ipad/#post-10065085

[bamboozle]

I should probably have included the following...

Steps to replicate

Open the demo site (​https://2017.wordpress.net/) on iOS and scroll down the page. The header image has the parallax effect, but subsequent images further down the page do not.

[bamboozle]

Hi there, I was just wondering how long it might take for someone to take a look at this. Any help would be very much appreciated - thanks.

[joyously]

I have to wonder if this is a design decision, because it behaves the same on stock Android browser also. Mobile device browsers are known to treat fixed background images differently due to the nature of the viewport.
Feel free to submit a patch if you know how to fix it.

[bamboozle]

Thanks for your reply, much appreciated. I did wonder this myself but was unable to find any documentation. I have no idea how this would be patched.

I realise that this is a free/bundled theme however, since most website traffic is now mobile in nature (for the majority of websites, at least), it does seem quite limiting.

I would be interested to find out if there are any plans for changes to iOS or Android that may enable this feature to work on all images. Again finding out any relevant information on this has proved difficult.

I have also noticed that the tablet preview button in WordPress shows all images with the parallax effect.

[melchoyce]

Hi there!

This was an intentional decision. background-attachment: fixed; isn't supported on iOS, and ends up distorting the image, so it was disabled.

You can see more background on the issue here: #38395.