Actually, the \setuplocalinterlinespace[line=4.2ex] command allowed me to get what I wanted.
Thank you very much !
What I did (see below for the interested) is I put
before={\setuplocalinterlinespace[line=2.8ex]\blank[halfline]
to change the interline space of titles, but I also added
after={\setuplocalinterlinespace[line=4.2ex]
in order to put it back to the global setting of the page.
That way, it interferes less with the rest of the layout, and I don't have to reajust interline spacing everywhere.

Again, thanks for your help, it is greatly appreciated.


\setupinterlinespace[line=4.2ex]  

\setuplabeltext[chapter=CHAPITRE~]
\setupcombinedlist[content][level=3,alternative=c,]
\define[3]\ChapterList{
\setuplocalinterlinespace[line=2.8ex]
\blank
\par\noindent\currentlistsymbol\crlf
#2\enspace\listdots\enspace
#3\par
\setuplocalinterlinespace[line=4.2ex]
}
\setuplist[chapter][
label=yes,
alternative=command,
command=\ChapterList,
]
\setuplist[section][
before={\setuplocalinterlinespace[line=2.8ex]\blank[halfline]},
margin=0cm,
width=1.25cm,
distance=0cm,
after={\setuplocalinterlinespace[line=4.2ex]},
]
\setuplist[subsection][
before={\setuplocalinterlinespace[line=2.8ex]\blank[halfline]},
margin=1.25cm,
after={\setuplocalinterlinespace[line=4.2ex]},
]
\starttext

\completecontent

\startbodymatter
\chapter{THIS VERY VERY VERY VERY VERY VERY LONG TITLE SHOULD BE SINGLE INTERLINE-SPACED (line=2.8ex)}
\section{THIS VERY VERY VERY VERY LONG TITLE SHOULD BE SINGLE INTERLINE-SPACED (line=2.8ex)}
\subsection{THIS VERY VERY VERY LONG TITLE SHOULD BE SINGLE INTERLINE-SPACED (line=2.8ex)}
\stopbodymatter

\stoptext 




Mathieu




> From: context@st.estfiles.de
> Date: Wed, 25 May 2011 10:04:04 +0200
> To: ntg-context@ntg.nl
> Subject: Re: [NTG-context] TOC : Changing the interline spacing of titles, for long titles on multiple lines
>
>
> Am 25.05.2011 um 00:18 schrieb Mathieu DUPONT:
>
> >
> > Hi,
> >
> > Is there a way to have, in the table of contents, the titles (of chapters, sections, subsections, etc.) with a different interline spacing than the rest of the TOC ?
> > My TOC interline spacing is set at 1.5 (4.2ex), but I would like to have the long titles on multiples lines being only single interline spaced (2.8ex).
> > Is there something I could add in the \setuplist[chapter] command ?
> >
> > Thanks for any hint !
>
>
>
> Something like this?
>
> \setuplist[chapter][
> label=yes,
> alternative=c,style={\switchtobodyfont[10pt]\bf\setuplocalinterlinespace[line=4.2ex]},
> before={\blank[line]},after={\blank[halfline]}
> ]
>
> \setuplist[section,subsection][
> label=yes,
> alternative=c,style={\switchtobodyfont[10pt]\setuplocalinterlinespace[line=2.8ex]},
> before={\blank[line]},after={\blank[halfline]}
> ]
>
> \starttext
>
> \completecontent
>
> \startbodymatter
> \chapter{THIS VERY VERY VERY VERY VERY VERY VERY VERY LONG TITLE\\SHOULD BE BOLD INTERLINE-SPACED (line=4.2ex)}
> \section{THIS VERY VERY VERY VERY LONG TITLE SHOULD BE SINGLE INTERLINE-SPACED (line=2.8ex)}
> \subsection{THIS VERY VERY VERY VERY LONG TITLE SHOULD BE SINGLE INTERLINE-SPACED (line=2.8ex)}
> \stopbodymatter
>
> \stoptext
>
>
>
> Steffen
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
>
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage : http://www.pragma-ade.nl / http://tex.aanhet.net
> archive : http://foundry.supelec.fr/projects/contextrev/
> wiki : http://contextgarden.net
> ___________________________________________________________________________________