[luatex] The effect of \pardir on \leftskip versus \parshape

Joseph Wright joseph.wright at morningstar2.co.uk
Fri Dec 7 10:36:02 CET 2012

On 07/12/2012 07:34, Taco Hoekwater wrote:
> On 12/07/2012 08:09 AM, Joseph Wright wrote:
>> On 06/12/2012 22:42, Joseph Wright wrote:
>>> Hello all,
>>> Playing around with RTL primitives, I find something a bit strange, or
>>> at least unexpected, with the treatment of paragraph parameters. In the
>>> following, "\pardir TRT" swaps the effect of \leftskip and \rightskip,
>>> which I can understand, but leaves the indent set up by \parshape on the
>>> 'absolute' left (\hangindent is the same). Is this deliberate, and if so
>>> is it documented (Omega manual?).
> As far as I know, that was not documented. I cannot even see from the
> source whether the curent behaviour was intentional or missed case. But
> the real question is: does it need changing?
> Best wishes,
> Taco

Hello Taco,

As I'm not a RTL user, I can only give a rather limited answer to that.

I'd say \leftskip and \rightskip make most sense as 'absolute' page
sides, not to the 'start of text line' and 'end of text line'. The names
does say 'left' and 'right', after all.

The case with \hangindent/\parshape is more tricky, but the description
in The TeXbook does talk about indenting from 'the left margin' rather
than 'the start of the line'. I can see the argument here that as
Knuth's TeX only does LTR this is understandable but not relevant to RTL

However, any change would presumably break stuff. More importantly, I've
no idea what really makes sense in describing a RTL page. So I guess my
bottom line is 'What do the experts think?'.
Joseph Wright

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