
\setuplayout[width=middle,header=0pt,footer=0pt]

\startluacode 
  fonts.expansions.classes['big-expansion'] = {
    stretch = 4, shrink = 4, step = .5, vector = 'default', factor = 5
  }
\stopluacode

\definefontfeature
  [extraexpansion][default]
  [expansion=big-expansion] 

\usetypescript[pagella]
\setupbodyfont[pagella,13.4pt]

% \setupalign[hz,hanging,stretch]

\definetolerancemethod
  [horizontal] [extraspace]
  {\spaceskip.35em plus.25em minus.2em\relax}

\definetolerancemethod
  [horizontal] [extrastretch]
  {\emergencystretch=18pt}

\definestartstop
  [SloppyPar] 
  [before={\start
      \setuptolerance[horizontal,extrastretch,extraspace]
      \setfontfeature{extraexpansion}}, % changes nothing
   after=\stop]

\overfullrule=6pt


\starttext \showframe[text]

\startcolumns[balance=no]
\startSloppyPar
  {\bf sloppy:}\par
  \input tufte \par \it \input knuth
\stopSloppyPar
\column
{\bf normal:}\par
\input tufte \par \it \input knuth 
\stopcolumns

\stoptext

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