[XeTeX] Arabic fonts and line heights

[Zdenek Wagner]

2013/1/12 Nathan Camillo Sidoli <sidoli at waseda.jp>:
> This may not actually be a xetex question, but I suspect I may get a useful
> answer here.
>
> Is there someway I can more accurately control the line height when using an
> Arabic font? When I use certain Arabic fonts, such as Amiri, which stack a
> lot in certain situations, I get very mixed line heights. The effect of this
> is that in entire pages of Arabic some lines are bunched together and others
> are more spread out, while in pages where Arabic words are quoted and
> phrases in generally English text the will sometimes create large gaps
> between the lines. I can get rid of this effect by correcting with something
> like scale=.8, but this makes the Arabic text so small as to be almost
> unreadable.
>
> Is there some way I can force the text to observe certain line heights, or
> at least make them all the same on each individual page?
>
This is a basic plai TeX question. The vertical list is composed so
that the distance of the baselines is equal to \baselineskip. However,
if the distance of the lower edge of the upper line from the top edge
of the lower line is less than \lineskiplimit, the lines are
positioned so that the distance between the bottom of the upper line
and the top of the lower line is equal to \lineskip. It happens in
Urdu where Nastaleeq style is used and for instance مجھے is
practically vertical.

You can play with these dimen registers. You have not written whether
you use plain XeTeX or XeLaTeX. In XeLaTeX some macros change the
values of these registers, you have to use the LaTeX way so that LaTeX
knows that you wish to use values other than the default.

> Thanks,
>
> Nathan
>
>
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Zdeněk Wagner
http://hroch486.icpf.cas.cz/wagner/
http://icebearsoft.euweb.cz