For discussion of OFFICE-4030 and OFFICE-3791

[Regina Henschel <regina.henschel@libreoffice.org>]

Hi all,

I have put Miklos Vajna, proposal owner of OFFICE-4030, in CC.

In regard to OFFICE-4030 Bottom to top, left to right writing direction:
For the intended purpose it is not enough, to describe the writing-mode 
as "bt-lr". You need to define the glyph orientation in addition.

Alternatives:
A)
Add the values from 
https://www.w3.org/TR/2001/REC-xsl-20011015/sliceA.html#writing-mode-add, 
at least the value bt-lr and tb-lr,
and in addition specify an equivalent to 
https://www.w3.org/TR/2001/REC-xsl-20011015/slice7.html#writing-mode
7.27.2 "glyph-orientation-horizontal"
and
7.27.3 "glyph-orientation-vertical"

B)
Extend the current values of writing-mode with own variants, which 
include glyph orientation. Read an outline below.

C)
Use CSS and SVG properties directly. 
https://www.w3.org/TR/css-writing-modes-3/.
See also https://svgwg.org/svg2-draft/text.html#WritingModeProperty
It will use 'writing-mode', 'direction', and 'text-orientation'. It will 
be different from CSS2 and SVG1. It is complex. I think it is not really 
suitable, but decide yourself.


ODF1.3, part3, 20.404 style:writing-mode
========================================
A writing-mode value consists of a first part for inline progression, a 
second part for block progression and an optional third part for glyph 
orientation. The parts are connected by an hyphen.

A progression is either a horizontal direction or a vertical direction. 
A horizontal direction is one of
lr: from left to right
rl: from right to left
A vertical direction is one of
tb: from top to bottom
bt: from bottom to top
A writing-mode value combines a horizontal progression with a vertical 
progression.

If a glyph orientation part is missing, a linguistic (typographic?) 
glyph orientation is used. That means, that rotation of a glyph is 
determined by the script used for the language of the text. Consumers 
should consider the rules and algorithms of the Unicode standard.
[e.g. http://www.unicode.org/reports/tr41/ Common References for Unicode 
Standard Annexes, [UAX50], [UTS37]].

If a glyph orientation part is given, a geometric glyph orientation is 
used. That means, that all glyphs are rotated as specified, no glyph has 
a special rule. Possible glyph orientations are
turn0: No glyph is rotated
turn90: All glyphs are rotated 90degree clockwise
turn180: All glyphs are rotated 180degree
turn270: All glyphs are rotated 90degree counter-clockwise.
The angles are relative to the glyph as given in the Unicode charts.

Default value for writing-mode is "lr-tb".

Consumers shall at least support one of the writing-mode values "lr-tb", 
"rl-tb" and "tb-rl".

The following shorthands are allowed: "lr" for "lr-tb", "rl" for "rl-tb" 
and "tb" for "tb-rl".


[The value 'page' is missing here and needs to be added.]



[For defining of 'inline progression', 'block progression' and 'glyph 
orientation' see http://unicode.org/notes/tn22/. That has a link to a 
pdf-file http://unicode.org/notes/tn22/RobustVerticalLayout.pdf. In that 
pdf, section 'Analyzing Text Flow'. Bibliography: Etemad, Elika J., 
Robust Vertical Text Layout. 27th Internationalization and Unicode 
Conference. Berlin, Germany, April 2005
In CSS3 it is named 'inline base direction' and 'block flow direction' 
respectively.]


Examples
linguistic
"lr-tb"     Latin, Greek
"rl-tb"     Arabic, Hebrew
"tb-rl"     Japanese    OOXML "eaVert"
"tb-lr"     Mongolian   OOXML "mongolianVert"
"bt-lr"     Batak

geometric
"tb-rl-turn90"      OOXML "vert"
"bt-lr-turn270"     OOXML "vert270"
"tb-lr-turn0"       OOXML "wordArtVert"
"tb-rl-turn0"       OOXML "wordArtVertRtl",

"tb-lr-turn0" and "tb-rl-turn0" would be similar to ODF 1.3,part 3, 
20.263 style:direction, value "ttb", but not restricted to 
table-cell-properties and chart-properties.

[some Examples are from https://www.omniglot.com/writing/direction.htm]
[OOXML values are from ST_TextVerticalType in section 20.1.10.83, 
ISO/IEC 29500-1:2016]

Kind regards
Regina