PDF: experimental feature - vertical layout

[Intelligent2013]

Need add support for vertically oriented text for Japanese documents, for instance: (example from https://www.antennahouse.com/hubfs/xsl-fo-sample/language/writing-mode-1.pdf)

Apache FOP doesn't support a vertical direction property (tb-rl), see https://xmlgraphics.apache.org/fop/2.9/complexscripts.html#writing_mode_property.

Need try to check that Japanese vertical layout can be achieved with two steps:

• turn each character in 90 degrees
• turn page in 90 degrees

[Intelligent2013]

turn each character in 90 degrees

In XSL-FO there reference-orientation property, but it relates to the 'area', not for one glyph (https://www.w3.org/TR/2001/REC-xsl-20011015/xslspec.html#reference-orientation).

(In AH there is glyph-orientation property https://www.antennahouse.com/hubfs/xsl-fo-sample/character/glyph-orientation-1.pdf?hsLang=en)

There is one more idea - replace each character by SVG with text rotating instruction:

<svg xmlns="http://www.w3.org/2000/svg">
  <text transform="rotate(90)">B</text>
</svg>

[Intelligent2013]

I've tried to replace each character to the SVG with rotated text (one character):

<fo:instream-foreign-object fox:alt-text="{.}">
<svg xmlns="http://www.w3.org/2000/svg" width="15" height="15">
<text font-size="14pt" transform="rotate(-90,15,0)"><xsl:value-of select="."/></text></svg>
</fo:instream-foreign-object>

and the resulted PDF looks so: (Note: I know that some English letters didn't rotated.)

Issues:

• too small space between glyph, need to increase it (emulate font glyph distance via SVG property?)
• English glyphs didn't aligned horizontally

• overlapped bottom page margin (looks like it's Apache FOP bug, I don't figure out how to fix it)

• wrong PDF comments position

• I don't sure at all that table auto-layout algorithm will be work properly.

So, this approach is waste of time. It generates a bunch of bugs. Emulate glyph properties via SVG markup is very complicated idea.