[NTG-context] MetaFun - "remove the paths of text" from a rectangle to let the background visible

[Taco Hoekwater]

> On 24 Dec 2020, at 00:14, Garulfo <garulfo at azules.eu> wrote:
> 
> Thanks Taco,
> 
> I made some progress :
> https://wiki.contextgarden.net/Talk:Cover_Pages
> 
> I now have two additional questions ... ;-)
> 
> - How can I deal with "space" characters (because current solution
>  requires to explicitly add the ~ character)

Here’s what I would do (which is probably not the nicest way of doing it). Just
enable \obeyspaces while reading the argument to \EmptyLetters, then disable
it again immediately (that is needed if you have to go back to TeX from Lua):

\def\EmptyLetters
 {\obeyspaces\doEmptyLetters}

\def\doEmptyLetters#1%
  {\normalspaces
   ...
  }

and in \whatever you then need \doifinstringelse{ }{#1}

Best wishes,
Taco