Re: \noindentation not working

[Hans Hagen <j.hagen@xs4all.nl>]

On 11/20/2020 6:27 PM, Wolfgang Schuster wrote:
> Pablo Rodriguez schrieb am 20.11.2020 um 17:41:
>> Dear list,
>>
>> I have the following MWE:
>>
>>    \showframe\showgrid
>>    \setupindenting[yes, always, big]
>>    \starttext
>>    \noindentation
>>    a
>>
>>    a
>>    \stoptext
>>
>> Using LMTX (2020.11.19 11:28), I get indentation with \noindentation.
>>
>> Could anyone confirm this?
> 
> Yes, something is wrong.
> 
> %%%% begin example
> \showgrid
> 
> \starttext
> 
> \parindent\emwidth
> 
> a
> 
> \everypar{\setbox\scratchbox\lastbox}
> a
> 
> \stoptext
> %%%% end example

Ah, okay. We have normalization enabled now. That means two things:

- instead if a hbox being used for indentation (with >= 0 width) we now 
have a skip (with no stretch but that might become an option some day); 
the tex engine uses a hbox because it is easier on the par builder (less 
checking, as glue, being a valid breakpoint, involves quite a bit)

- after breaking a paragraph into lines the result is normalized, that 
is: we have left/right hang, left/right skip. left/right parfilskip 
instead of a mix of either or not present left/right skip, and shifted 
boxes in case of some hang features (again, the original approach is 
easier for the engine, but machines are fast enough and have plenty of 
memory so we can stop worrying about it)

The ideas is that this way we can make some lua nodelist hackery more 
elegant (but I need to catch up with that: most tex files are now split 
in mkiv and lmtx and next comes the lua files after which we can start 
some more drastic upgrading ... keep in mind that quite some code is 
from more than a decase ago, evolved a bit but seldom changed conceptually).

Here's a fix:

\unprotect

\def\spac_indentation_remove
   {\ifzeropt\parindent \else
      \begingroup
      \unskip % we also need to check for the subtype
      \setbox\scratchbox\lastbox % we also need to check for the
      \endgroup
    \fi}

\protect

(we might need adapt some more code); actually more correct would be:

\def\spac_indentation_remove
   {\ifzeropt\parindent \else
      \begingroup
      \ifnum\lastnodetype=\gluenodecode
        \unskip % we also need to check for the subtype
      \orelse\ifnum\lastnodetype=\hlistnodecode
        \setbox\scratchbox\lastbox % we also need to check for the subtype
      \else
        % forget about it
      \fi
      \endgroup
    \fi}

(it actually makes sense to have a native \unindent primitive but we can 
simulate that in lua)

Hans

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                                           Hans Hagen | PRAGMA ADE
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