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

[Joseph Wright]

On 07/12/2012 13:17, Khaled Hosny wrote:
> Being named left and right does not necessarily mean they don't
> actually mean start and end, after all who named them was only
> considering left to right, top to bottom setting.

Also a perfectly reasonable position.

> Now, if I understand
> \left and \rightskip correctly, it seems like something one wants to
> mirror with directional change, otherwise one would want to explicitly
> adapt styles depending on text directionality, which is not something I
> really like (especially when dealing with something like LaTeX styles
> that are PITA to modify).

I'm not sure that follows at an engine level (LaTeX2e's deficiencies are
a different matter). If you think about sitting down with a piece of
paper to design a layout, the text direction does not affect which side
of the paper is the left, and therefore a design description may well
refer to 'left' and 'right' of the page whether the dominant direction
is LTR or RTL.

> In general the layout in right to left settings is usually an identical
> mirror of left to right one (including the position of odd and even
> pages).

That's only true if you are assuming you are producing both LTR and RTL
documents from one design spec: seems unlikely.

> We also need to consider top to bottom directionality, which I
> suspect is handled the same.

Needs people with expertise in that area, which I certainly don't have.
I can't imagine paragraphs in vertical typesetting, but I may be wrong.
-- 
Joseph Wright