Re: [Dev-luatex] LuaTeX doesn't discard empty paragraphs when textdir is used

On Mon, Aug 2, 2021 at 5:52 PM Marcel Fabian Krüger wrote:

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On Mon, Jun 21, 2021 at 5:03 PM Marcel Krüger wrote:

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Hi,

consider the following plain LuaTeX document:

\textdir TRT \noindent\par \bye

without the `\textdir TRT` line or with `\textdir TLT`, this would lead to "warning (pdf backend): no pages of output.", but with the non default "\textdir", it creates an empty (except for the page number)

On Thu, Jul 29, 2021 at 09:54:20AM +0200, luigi scarso wrote: page

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instead.

This can be avoided by setting \pardir too:

\textdir TRT\pardir TRT \noindent\par \bye

again produces no output, but adding a group around it reintroduces the issue:

\begingroup \textdir TRT\pardir TRT \noindent\par \endgroup \bye

leads to an empty page.

Of course similar things happen not only for otherwise empty documents: Instead of empty paragraphs disappearing, they add empty lines.

Together, this is not only inconsistent with other engines which always discard empty paragraphs, but also leads to hard to predict behavior (especially for users who are not familiar with the implementation of LuaTeX's directional system), so I think it would be great if LuaTeX could always remove such empty paragraphs.

(sorry for the delay) Do you have a patch to propose ?

I attached a patch which adds a \emptyparmode parameter with three possible states:

- 0: Never ignore empty paragraphs. Not sure if this is useful, but it seemed like an obvious thing to add. - 1: The default: A paragraph is empty is it contains at most one node. This is the old behavior. - 2: A paragraph is empty if it only contains local_par and dir nodes. This is what I would consider the expected behavior.

Best regards, Marcel

Thank you ! -- luigi