[css-writing-modes-3] Position of vertical scrollbar in documents where principal writing-mode is 'vertical-rl' or 'sideways-rl'

Elika, Koji,

Since inline flow direction is from-top-to-bottom and since block flow 
direction is from-right-to-left for documents with principal 
writing-mode set to 'vertical-rl' or to 'sideways-rl', then when 
inline-size of a  'vertical-rl' or 'sideways-rl' block is greater than 
viewport, then the vertical scrollbar should be located at block-end 
side which is the left-hand side and not the right-hand side.

Please load this reference file in Firefox 48+:

http://www.gtalbot.org/BrowserBugsSection/CSS3WritingModes/s732-sizing-phase-ortho-vrl-002-ref.xht

In Firefox 48+ in about:config, if I set layout.scrollbar.side to 0 
(which is the default), then the vertical scrollbar is on the right-hand 
side of the viewport.

Still in Firefox 48+ in about:config, if I set layout.scrollbar.side to 
1, then the location of the vertical scrollbar will be on the left-hand 
side in Firefox, which is where it should be.

- - - - - - -

Possible layout.scrollbar.side values and their effects

0
Place the scrollbar at the end (right in LTR languages, left in RTL) of 
the content, based on the UI's direction. (Default)


1
Place the scrollbar at the end (right in LTR languages, left in RTL) of 
the content, based on the document/content's direction.


2
Place the scrollbar on the right side of the content.


3
Place the scrollbar on the left side of the content.

coming from
http://kb.mozillazine.org/Layout.scrollbar.side#Possible_values_and_their_effects

- - - - - - -

In my opinion, the best setting for layout.scrollbar.side and for 
testing each and all writing-mode values is 1

Now, if you load

http://www.gtalbot.org/BrowserBugsSection/CSS3WritingModes/s732-sizing-phase-ortho-vrl-002-ref.xht

in Chrome 53+, the vertical scrollbar will be on the right-hand side.

Q1: In Chrome, is there a chrome://flags/ equivalent to Firefox's 
layout.scrollbar.side (and where the setting matches value = 1 based on 
the document/content's direction)? I searched and could not find any.

Q2: What is the layout.scrollbar.side setting in Firefox when Mozilla 
does automated testing?

I believe the proper, most adequate, most logical and reasonable 
position of a vertical scrollbar for 'writing-mode: vertical-rl' and 
'writing-mode: sideways-rl' when inline-size is greater than viewport 
should be located at block-end side which is the left-hand side and not 
the right-hand side.

As far as I can see, MS-Edge 13 also positions the vertical scrollbar on 
the left-hand side in that s732-sizing-phase-ortho-vrl-002-ref reference 
file.

Gérard
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Received on Monday, 5 September 2016 07:06:33 UTC