Hi:

WOW! This is very impressive! Thanks for your work.

So I think we can add vertical CJK typesetting feature to LuaTeX/MKIV
next year?

[Wolfgang is busy writing the wishlist for cjk typesetting, so i think
he will be very interested in experimenting your results]

Yue Wang

On Tue, Dec 30, 2008 at 4:08 PM, Arthur Reutenauer
<arthur.reutenauer@normalesup.org> wrote:

Can you show me an example of vertical typesetting in LuaTeX?

Try the attached file.  It demonstrates vertical typesetting with LuaTeX in

three steps; unfortunately it only works in DVI mode for the moment

because the PDF output is completely buggy, I discussed with Taco about

that.

1. At first, you simply need to switch to vertical directions, using the

primitives inherited from Omega.  Here I used LTL as the general direction: the

first letter indicates the first edge of the page is at the left (lines of text

move globally from left to right); 'T' means the second edge of the page is at

the top (inside a single line, text moves from the top downwards).  The last

letter defines the notion of "top" for individual letters, I chose left, more

or less randomly.  It has some influence, as we will see later, but not as much

as the first two letters.

Then you can set English text vertically, with the columns running from left

to right.  It's akward to use OpenType fonts in DVI mode, so I simply used

Computer Modern Typewriter, stacking the letters on top of each other.  Of

course it's weird to set English text vertically without rotating the letters,

but it is possible.  There is a problem, though, because the text looks

completely clumsy: the reason is the font's metrics are not designed for

vertical typesetting, so you need to change them.  The way metrics work in

Omega's directional model is that width runs along the direction of the line,

here top-to-bottom; hence a glyph's width, in that example, is actually the sum

of its height and its depth in the original font designed for horizontal

typesetting. Its height and depth, in turn, need to be chosen so that their sum

is equal to the horizontal width, and I think it's a good choice to make them

equal to each other, so that each glyph is centered on the vertical base line.

2. On the second page I demonstrate a first way to do that, with Lua code:

you can use the define_font callback to redefine width, height and depth for

each glyph in the font, and LuaTeX will use these new metrics.

Note that the vertical width should, actually, be a little bit more than

horizontal height + horizontal depth, because these dimensions are not meant to

blend well with stacks of letters, unlike the horizontal width: the former are

really more like the dimensions of a bounding box, whereas the latter is the

distance by which you should advance the line of text in order for the text not

to look to crowded.  Thus, I cheated a bit, by stretching the vertical width by

30% (chosen, again, at random by trial and error).

But that's still not enough: as you can see, letters with descender, like 'g'

in the first line, sticks into the next letter.  That's because it has a

horizontal depth, and its origin is thus too low with respect to its enclosing

box: we need to raise those letters by their horizontal depth.

3.  We could do this by editing the font and modify every glyph so that it

sits on the baseline, but we can do better by using virtual fonts.  In LuaTeX,

there are two ways to use virtual fonts: you can use a .vf file, or you can

define it with Lua commands in the font data.  Unfortunately, the latter

doesn't work in DVI mode because your Lua code is lost once the DVI file is

produced, and your DVI reader / driver doesn't know how to create the font, so

we have to stick to the traditional method and produce a .vf file.  I wrote a

small script to that effect which you will find in the attached zip, but the

.vf and .tfm files are also attached anyway.  Now the text looks quite nice, in

my opinion.  It's still hard to read, but that's of course because English is

not supposed to be typeset that way.

The (figurative) bottom line of all this is that you need to typeset vertical

text with fonts that have vertical metrics.  Once the problems with PDF mode

are fixed, I can try and do that with Chinese or Japanese fonts; I expect it

would be quite straightforward.

      Arthur

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