[NTG-context] expansion problem: random location

Henning Hraban Ramm texml at fiee.net
Fri Sep 13 18:51:52 CEST 2019


Hi, in an example document I’m trying to get pictures of random size and placement.
Unfortunately the expansion is over my head:

%%%%%%%%%%%%%%%%%
\useMPlibrary[dum]
\usemodule[visual]

\startluacode

local locations = {
  'top',
  'bottom',
  'left',
  'right',
}

function RandomLocation()
  context(locations[math.random(1,#locations)])
end

\stopluacode

\newdimen\PicWidth
\PicWidth=\textwidth

\define[1]\Blindbild{
\getrandomnumber\imgH{1}{9}
\PicWidth=\textwidth
\doif{#1}{left}{\PicWidth=.4\textwidth}
\doif{#1}{right}{\PicWidth=.4\textwidth}
\startplacefigure[location={#1},title={#1 \fakewords{3}{20}}]
\externalfigure[place #1][width=\PicWidth,height=\dimexpr\textheight * \imgH / 10 \relax]
\stopplacefigure
}

\starttext
   \dorecurse{3}
     {\chapter{\fakewords{5}{10}}
       \dorecurse{3}
         {\dorecurse{3}{\fakewords{50}{100}\endgraf}
            \Blindbild{\ctxlua{RandomLocation()}} % expansion!?
            \dorecurse{2}{\fakewords{50}{100}\endgraf}}}
\stoptext
%%%%%%%%%%%%%%%%%%

So the parameter of \Blindbild should get generated at the time of calling the macro, so that #1 stays the same within the macro.
In this state the Lua function gets called at every use of #1.


Greetlings, Hraban
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