[NTG-context] About the use of command handlers

[Hans Hagen]

On 5/29/2020 6:29 AM, Jairo A. del Rio wrote:
> Hello list! I was reading the following:
> 
> https://wiki.contextgarden.net/Style_Alternatives
> 
> I wanted to figure out how to make a simple module. However, there's a 
> point in the example below which I don't understand
> 
> % macros=mkvi
> \startmodule[look]
> \unprotect
> \writestatus{loading}{ConTeXt User Module / look} 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> \installnamespace {look}
> \installcommandhandler \????look {look} \????look
> 
> \appendtoks
> \setuevalue{\currentlook}{\do_look{\currentlook}}
> \to \everydefinelook
> 
> \unexpanded\def\do_look#id{%
> \edef\currentlook{#id}%
> \dosingleempty\do_do_look%
> }
> 
> \def\do_do_look[#parms]#content{%
> \begingroup
> \iffirstargument\setupcurrentlook[#parms]\fi
> %This handles style and color
> \uselookstyleandcolor\c!style\c!color%
> #content%
> \endgroup%
> }
> 
> \protect %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> \stopmodule
> 
> What have I to do if, instead of "color" or "style", I want to use 
> another keyword, as "dummy" and get its value? Something like
> 
> \definelook[lol][dummy = blabla]
> \lol{words}
> %e.g. words \emph{blabla} or something similar
> so "lol" is a word, a number or whatever. I've read something about 
> command handlers, but I'm having a hard time trying to understand them. 
> Thank you in advance!
% macros=mkvi

\unprotect

\installnamespace {look}

\installcommandhandler \????look {look} \????look

\appendtoks
     \setuevalue{\currentlook}{\module_look_do{\currentlook}}
\to \everydefinelook

\unexpanded\def\module_look_do#id%
   {\edef\currentlook{#id}%
    \dosingleempty\module_look_do_do}

\def\module_look_do_do[#parms]#content%
   {\dontleavehmode
    \begingroup
    \iffirstargument
      \setupcurrentlook[#parms]%
    \fi
    \doifsomething{\lookparameter{title}}
      {\begingroup
         \uselookstyleandcolor\c!headstyle\c!headcolor
         \lookparameter{title}%
         \lookparameter{separator}%
       \endgroup}%
    \uselookstyleandcolor\c!style\c!color
    #content%
    \endgroup}

\protect

\starttext

\setuplook[separator={: }]

\definelook[lol][color=red,headcolor=green]

\lol[title=blabla]{words}

\stoptext



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