Re: LMTX problem with doifmode in \setuplayout

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

On 6/8/2021 10:11 PM, Wolfgang Schuster wrote:
> Rik Kabel schrieb am 08.06.2021 um 18:14:
>>
>> Hello all,
>>
>> Odd issue with LMTX (works fine with --luatex). \doifelsemode causes a 
>> failure if it is used to set a simple value such as on, off, yes, no, 
>> ..., but works with a dimension. Perhaps better illustrated by an example:
>>
>>     \definemode        [aaa]
>>                        [keep]
>>     \setuplayout       [
>>                         marking=\doifmodeelse{aaa}{off}{on},
>>     %                   marking=on,
>>                         grid=\doifmodeelse{aaa}{yes}{no},
>>     %                   grid=yes,
>>                         bottom=\doifmodeelse{aaa}{10mm}{20mm},
>>                        ]
>>     \starttext
>>        This is only a test.
>>     \stoptext
>>
>> The problem occurs whether or not the mode is enabled. In the example, 
>> it fails with the mode test in the either the marking= or grid= keys, 
>> but has no problem with it in the bottom= key.
>>
>> The error message says:
>>
>>     The control sequence marked <to be read again> should not appear
>>     between \csname and \endcsname.
>>
>> pointing to the enabled \doifmodeelse line.
>>
>> The same issue occurs with the following, using \doifmode:
>>
>>     \definemode        [aaa]
>>                        [keep]
>>     \setuplayout       [
>>                         marking=on,
>>                         marking=\doifmode{aaa}{off},
>>                        ]
>>     \starttext
>>        This is only a test.
>>     \stoptext
>>
>> This did work without complaint a few months ago.
>>
> 
> You can never be sure if these combinations (\doifXXX within \setupXXX) 
> work without problems. The only reliable method in this case is:
> 
> % default setup
> 
> \setuplayout
>      [marking=on]
> 
> % mode dependent setup
> 
> \startmode[aaa]
> 
>      \setuplayout
>          [marking=off]
> 
> \stopmode
Indeed. I'll make the test more robust (not come up with an error) but 
as Wolfgang says, it won't work anyway because \doifmode is a protected 
macro.

There is actually a trick:

   \expand\doifmode{aaa}{on}

will ignore the protection .. compare

   \edef\foo{\doifmode{aaa}{on}}        [[\meaningless\foo]]

   \edef\foo{\expand\doifmode{aaa}{on}} [[\meaningless\foo]]

only in luametatex/lmtx

Hans

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                                           Hans Hagen | PRAGMA ADE
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