> Le 7 juin 2020 à 23:19, Aditya Mahajan <adityam@umich.edu> a écrit :
> 
> On Sun, 7 Jun 2020, Fabrice L wrote:
> 
>> Dear List,
>> 
>> I would like to insert a page using (ideally) start/stop instructions. The problem is that this page should be inserted only in a certain mode. Consulting the mailing list, I thought the following code was working, but it’s not ! The code is executed in the mode as expected, but the following instructions ("Some other text... » in the exemple) is not typeset.
>> 
>> Here is a minimal (not working!) example:
>> 
>> % ————————————————————————————————————
>> \unexpanded\def\StartQuestionsList{
>> 	\startmode[ClassRoom]  \page[yes] Here are some questions: \blank
>> }
>> \unexpanded\def\StopQuestionsList{
>> 	\page[yes] \stopmode
>> }
>> \definestartstop[Questions][
>> 	before=\StartQuestionsList,
>> 	after=\StopQuestionsList
>> 	]
>> 
>> 
>> \startQuestions
>> 	Question A….
>> 	Question B….
>> \stopQuestions
>> 
>> Some other text...
>> % ————————————————————————————————————
>> 
>> 
>> So to be clear, I would like the result in the « ClassRoom » mode to be:
>> % ————————————————————————————————————
>> Here are some questions:
>> 
>> 	Question A….
>> 	Question B….
>> 
>> Some other text...
>> % ————————————————————————————————————
>> 
>> Otherwise to be:
>> % ————————————————————————————————————
>> Some other text...
>> % ————————————————————————————————————
> 
> If you only set `ClassRoom` mode at compile time (rather than setting and unsetting it the middle of the document), then you can do:
> 
> \definebuffer[Questions]
> 
> \startmode[ClassRoom]
> \define\StopQuestionsList {...}
> 
> \definestartstop[Questions][...]
> \stopmode
> 

Thanks to Aditya, I have succeeded, but it was not trivial for me. So, in case somebody someday would need a detailed solution, here is a minimal example, and an explanation. 

A buffer « Questions » is defined. If in « ClassRoom » mode, a start/stop « Questions » is also defined. So when ConTeXt encounters the \startQuestions / \stopQuestions, if the « ClassRoom » mode is enabled, the buffer is processed (with some format if needed - framed here for the example), and if the mode « ClassRoom » is disabled, then nothing is process. You can add as many \startQuestions / \stopQuestions you wish. 


% ----------------------------------------------
\definebuffer[Questions]

\enablemode[ClassRoom] % Try "On / Off » to process "\startQuestions / \stopQuestions » or not.

\startmode[ClassRoom]
 \definestartstop[Questions][before={\startframedtext\red},after={\stopframedtext\blue}]
\stopmode

\starttext

Before...

\startQuestions
	The content of the buffer ! 
\stopQuestions

After...

\stoptext
% ----------------------------------------------

Thanks Aditya !
Fabrice.



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