Invalid dropdown positioning when screen is scrolled

[Marek Lewandowski]

If you have a page with a longer content than your screen height, editors below "one screen height" will have dropdowns mispositioned.

1. Open any sample with CKEditor. (i.e. samples/replacebyclass.html)
2. Evaluate following code:

   ( function() {
   	// Increase description block height.
   	document.querySelector('.description').style.height = '3000px';
   	// Scroll down, lemme do it for you.
   	window.scrollTo(0,document.body.scrollHeight);
   }() );
   

3. Click font size dropdown.

As far as I've tested only Blink browsers seems to be affected by this issue (Chromium, Chrome, Opera). FF and IE8 were fine, don't know how about Safari.

This is a regress introduced in ​t/12747 ​git:5875b0cf0bd145156a25d60e4a4ae9afb543916b (not yet published).

[Marek Lewandowski]

It would be also nice to check if Safari is also affected, to know what tag should land in the title, but I don't have a mac right now by my hand.

[Jakub Ś]

Problem can be reproduced in Blink and Webkit browsers. In case of Webkit, I was able to reproduce this issue on Safari 7.0.6 (don't have anything newer) but not in Safari 5.1 (Windows).

[Jakub Ś]

This is a recent regression introduced by #12747.

[Artur Delura]

I made an experiment and created a file with scroll and also iframe with scroll, and checked to which elements body or html are set information about scrolling scrollLeft and scrollTop. I checked all abowsers (including quirks but compability mode only IE8). Results are various sometimes scroll information are set to html sometimes to body and to both. What is obvious is that at least in one element information is stored. So I just simplify getting scroll information by following code.

var scrollLeft = ( $docElem.scrollLeft || body.$.scrollLeft ),
    scrollTop = ( $docElem.scrollTop || body.$.scrollTop );

We don't need check whether we are in quirks mode.

I could write manual tests for this, because it's unreproducible.

[Artur Delura]

Changes in ​branch:t/12788.

[Piotrek Koszuliński]

Another DUP of #12758. Please work on this ticket there.