On 7/29/2021 9:54 AM, luigi scarso wrote:

On Mon, Jun 21, 2021 at 5:03 PM Marcel Krüger mailto:tex@2krueger.de> wrote:

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) page 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  ?

it's a side effect of the direction handler picking up states ... kind of tricky code but i can probably come up with a fix (maybe under parameter control) (of course normally a macro package will catch these kind of things if needed) Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------

Hi, 1) sometimes styles requires to use small vertical indentation between paragraphs and naturally  we choose to  use \parskip and it leads to some painful programming dealing with spaces For example after float if there will be paragraph  the space will be \|textfloatsep + \parskip. |The problem is that there is no control on this and I want to ask consider the possibility to add some  tokens list like \everyparskip{} which  would be inserted before \parskip where could be possible to check \lastskip: FOR EXAMPLE: \parskip=5pt \everypar{\showthe\lastskip} a \vskip20pt \showthe\lastskip b \showlists \bye STDOUT:

0.0pt. <everypar> \showthe \lastskip

<to be read again> a l.3 a ?

20.0pt. l.6 \showthe\lastskip

?

0.0pt. <everypar> \showthe \lastskip

<to be read again> b l.7 b POSSIBLE PLACE OF \everyparskip: .\tenrm a .\penalty 10000 .\glue(\parfillskip) 0.0 plus 1.0fil .\glue(\rightskip) 0.0 \glue 20.0 ----------- HERE \glue(\parskip) 5.0 \glue(\baselineskip) 5.05556 \hbox(6.94444+0.0)x469.75499, glue set 444.1994fil, direction TLT .\localpar ..\localinterlinepenalty=0 ..\localbrokenpenalty=0 ..\localleftbox=null ..\localrightbox=null .\hbox(0.0+0.0)x20.0, direction TLT .\tenrm b Or \everyparskip{} could be always in the format like \everyparskip{\vskip\parskip} and one could deal with it. Thanks, Linas ||

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

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

...

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) page 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

On Mon, Aug 02, 2021 at 05:55:18PM +0200, luigi scarso wrote:

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

...

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

I just noticed that my repo wasn't up-to-date, so here is the patch again after resolving a conflict with the partoken change. Marcel