[luatex] The effect of \pardir and \textdir on \indent and \parfillskip

[Joseph Wright]

On 12/12/2012 15:27, Ulrike Fischer wrote:
>>   \pardir TRT
>>   Hello world Hello world Hello world Hello world Hello world
>>   Hello world Hello world Hello world Hello world Hello world
>>   Hello world Hello world Hello world Hello world Hello world
>>   Hello world Hello world Hello world Hello world Hello world
>>   Hello world Hello world Hello world Hello world Hello world
> ...
>>
>> I find it surprising that the middle paragraph has the \indent on the
>> left, and that it's necessary to alter the text direction to get it on
>> the right.
> 
> Not only the indent is on the left. If you change the text to
> 
> \pardir TRT
>   A-Hello world Hello world Hello world Hello world Hello world
>   Hello world Hello world Hello world Hello world Hello world
>   Hello world Hello world Hello world Hello world Hello world
>   Hello world Hello world Hello world Hello world Hello world
>   Hello world Hello world Hello world Hello world Hello world-Z
> 
> You can see that also the "A" is on the left (and the Z on the
> right). So the direction of words are not changed. Only the lines
> are moved to the right -- which hasn't much effect on lines with a
> width equal to textwidth.

That's expected: \textdir is about the order of 'text-like objects
within the paragraph'. What I found odd was that I'd view the \indent as
a part of the 'shape within a paragraph', in the same way that say
\rightskip is (used to alter what happens *within* any 'outer' \parshape
or \hangindent). However, it's treated as part of the text itself, not
the shaping. May well make sense to others: I'm mainly trying to work
out 'how this is supposed to go' as there is not so much detail in the
docs I can find.
-- 
Joseph Wright