Vertical layout: using dedicated vertical presentation forms

[Intelligent2013]

Source issue: #226

From https://github.com/metanorma/docs/blob/main/109.adoc:

The renderer shall:

• Use dedicated vertical presentation forms when available

In the Table 2 implicitly there are two categories of glyph:

1. vertical orientation of the glyph can be get in two ways

   • the rotation 90 degrees clockwise, for instance U+300C LEFT CORNER BRACKET
   • using the dedicated glyph, for instance U+FE41 PRESENTATION FORM FOR VERTICAL LEFT CORNER BRACKET
     

2. vertical orientation of the glyph can be get by using the dedicated glyph only, because the rotation can't get the proper result, for instance U+3001 IDEOGRAPHIC COMMA should be replace by U+FE11 PRESENTATION FORM FOR VERTICAL IDEOGRAPHIC COMMA
   

The rendered PDF with the vertical layout example (we are interested in the first character):

• In case of the replacement the source character into the dedicated glyph for vertical form,
  If we copy the text and then paste into the text editor, then we'll see the 'left cornet bracket' as vertically oriented symbol:
  
  Also if we'll try to find the source text from adoc with the original character U+300C LEFT CORNER BRACKET, then the result will be empty.

• In case of the 'rotation 90 degrees clockwise', If we copy the text and then paste into the text editor, the we'll see the 'left cornet bracket' in the original form:
  
  And searching also will work.

As I noted above, there are characters which require to use the dedicated characters only.
I've found 8 characters only:

• U+3001 IDEOGRAPHIC COMMA (、) to U+FE11 PRESENTATION FORM FOR VERTICAL IDEOGRAPHIC COMMA (︑)
• U+FE50 SMALL COMMA (﹐) to U+FE10 PRESENTATION FORM FOR VERTICAL COMMA (︐)
• U+FE51 SMALL IDEOGRAPHIC COMMA (﹑) to U+FE11 PRESENTATION FORM FOR VERTICAL IDEOGRAPHIC COMMA (︑)
• U+FF0C FULLWIDTH COMMA (，) to U+FE10 PRESENTATION FORM FOR VERTICAL COMMA (︐)
• U+FF1A FULLWIDTH COLON (：) to U+FE13 PRESENTATION FORM FOR VERTICAL COLON (︓)
• U+FF1B FULLWIDTH SEMICOLON (；) to U+FE14 PRESENTATION FORM FOR VERTICAL SEMICOLON
• U+FF01 FULLWIDTH EXCLAMATION MARK (！) to U+FE15 PRESENTATION FORM FOR VERTICAL EXCLAMATION MARK (︕)
• U+FF1F FULLWIDTH QUESTION MARK (？) to U+FE16 PRESENTATION FORM FOR VERTICAL QUESTION MARK (︖)

We need to use these dedicated characters in any case. I.e. the copy-paste text and search features will not work properly (As I wrote due the different U+... codes in the original adoc text and resulted PDF).

Question: @ronaldtse does it make sense to use the rotation 90 degrees clockwise for the category 1. characters if we'll use, in any case, the dedicated characters for the category 2. ?

[ronaldtse]

@Intelligent2013 yes this is definitely an interesting discussion to be had.

When the these vertical Unicode glyphs were created, I don't think a lot of thought has been placed into the actual use cases, but were meant only for display purposes.

Indeed we have these categories:

1. Glyphs that the vertical forms are easily achieved through rotation. This way we can preserve easy searching. Technically, the "search implementations" should support searching both the vertical and horizontal variants of these glyphs, but we (can't) won't fight the current situation.
2. Glyphs that the vertical forms are dedicated and cannot be artificially "rotated" from the horizontal form. These we don't have a choice.
3. Glyphs that only have horizontal form without vertical form.

As you suggested, let's encode type 1 glyphs as rotated forms for ease of use.

In any case, this situation is due to vertical text support not well done in PDF viewers, it is not technically a problem.