Re: [NTG-context] Default values for key-value macros

10 Oct 2021


      On 10/10/2021 2:01 PM, noib3 via ntg-context wrote:
...
The way I've been defining key-value macros is to first pass them to 
Lua, handle the parsing there thanks to 
`utilities.parsers.settings_to_hash` and then assign the resulting Lua 
table to ConTeXt variables.
This worked fine up to now, but I'm having problems with the following MWE:
```
\def\style#1[#2] {
   \ctxlua{userdata.style([==[#2]==])}
   \placestyle
}
here you overload a core macro
...
\startluacode
   userdata = userdata or {}
  userdata.style = function(keyvals)
     local style = {
       color = nil,
       text = nil,
     }
     args = utilities.parsers.settings_to_hash(keyvals)
use "local args" here ^
...
    for k, v in pairs(args) do
       style[k] = v
     end
     context.setvariables({'style'}, style)
   end
\stopluacode
\define\placestyle{
   \doiftext
     {\getvariable{style}{text}}
     {\color[\getvariable{style}{color}]{\getvariable{style}{text}}}
}
\starttext
\style[
   text={Some red text},
   color=red,
]
\style[
   color=blue,
]
\stoptext
```
Here I assign a default value of `nil` to every key, and then check if 
the `text` variable is empty before printing it. I would expect the 
second macro not to print anything since its `text` should be nil, 
instead both macros print 'Some red text', the first one in red and the 
second one in blue.
context.setvariables

like any setting, it accumulates unless you group
...
I have attached a screenshot of the output.
What am I doing wrong?
local style = {
       color = "",
       text  = "",
     }

or you can go fancy with:

\startluacode
interfaces.implement {
     name      = "MyStyle",
     public    = true,
     protected = true,
     arguments = "hash",
     actions   = function(a)
         if a.text and a.text ~= ""  then
             if a.color and a.color ~= "" then
                 context.color( { a.color }, a.text)
             else
                 context(a.text)
             end
         end
     end
}
\stopluacode

\MyStyle[
   text={Some blue text},
   color=blue,
]

\MyStyle[
   color=blue,
]

\MyStyle[
   text={test \em test},
]


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