Big images makes editor scroll top on input in iPad with iOS 9.3.2

[pxdev]

Brief summary

If I have a big image in the editor and I open it in iOS 9, everytime I add a new letter to the editor the iframe is scrolled to the top, so I cannot see the inputted text.

Steps to reproduce

1. Create an editor with some content already added. This content should have at least one image with a big height. In some of my tests I used ​http://ckeditor.com/demo, I inspected the iframe and added the following property to the first image: height="720".

1.1 You can also use this codepen: ​http://codepen.io/anon/pen/WxzExZ/

2. Open the page in an iPad with iOS 9 (I'm using 9.3.2).
3. Scroll down until the image disappears from the screen.
4. Place the cursor at the end of some line and click some letter in the virtual keyboard.

4.1 In the codepen I wrote after the text: Do not create that page?

Expected result

The letter is written and the iframe is NOT scrolled at all.

Actual result

The iframe scrolls to the top, so I cannot see the letter I have just inputted. After this I cannot scroll the iframe at all.

Other details (browser, OS, CKEditor version, installed plugins)

I reproduce it in Safari in an iPad with iOS 9.3.2, using the latest CKEditor version with default plugins.

[pxdev]

I was able to reproduce it in iPhone simulator too.

Also, this issue might be related with the total scroll height and not just the image height, since using a small image but a lot of content also failed for me once.

[Jakub Ś]

This issue could be related or same as #10694

Other issues which concern scrolling on iPad are #11730 and #12749

[kkrzton]

As @j.swiderski mentioned, this issue is related to #10694. It might be a duplicate of it but it needs further investigation to be sure. Tested with iPad 9.3.1.

[m-turek]

I have checked this issue with latest CKEditor 4.6.2 on iOS 10.2.1 and Safari 10.0 (iPad). Reproduction steps are the same. The result is: when typing additional text, the editor's content is scrolled up to the beginning. It is also impossible to scroll the editor then. After typing another character the scroll is restored to correct position. Typing another character scrolls to the top again. Broken scroll occurs after every two characters of added text.

I have also checked on iOS 9.3.5 and Safari 9.0 Reproduction steps are the same. The result is: when typing additional text, the editor's content is scrolled up. It is also impossible to scroll the editor then. After typing another character the scroll position is changed (however the new typed text is not visible). Typing another character scrolls up again. Scroll position switches between two states after every input character.