Is it possible to align caption and caption text of figure(table) separately in ConTeXt?

Question

The align=center option of \setupcaptions can align the caption in the middle of figure or table. It's OK with one-line caption text, while not so good for multiple lines of caption texts, for all lines align in the middle.

How to make the effect like the following example, which the first words of caption text from the second line on line up with the first word after caption label?

Figure 1 This is very long caption text as 
         an example.

Answer 1

Starting with version 2019.12.27 19:26 of ConTeXt you can use \setupcaption[hang=yes] to have a hanging title for float captions.

\setupexternalfigures[location=default]

\setupcaption
  [figure]
  [align=tolerant]

\starttext

\startplacefigure[title={\samplefile{jojomayer}}]
  \externalfigure[hacker][width=.75\textwidth]
\stopplacefigure

\setupcaption
  [figure]
  [hang=yes]

\startplacefigure[title={\samplefile{jojomayer}}]
  \externalfigure[hacker][width=.75\textwidth]
\stopplacefigure

\stoptext

Answer 2

Right now that is only achievable by patching the core, but I've emailed the development list about this: https://mailman.ntg.nl/pipermail/dev-context/2019/003636.html

\unprotect

\def\strc_floats_make_complete_caption
  {\doifsomething{\floatcaptionparameter\c!spacebefore}{\blank[\floatcaptionparameter\c!spacebefore]}%
   \strc_floats_make_complete_caption_before
   \synchronizedisplaydirection % temp hack, till we have a proper model
   \noindent
   \gdef\lastcaptiontag{\strut\thecurrentfloatnumber}% was xdef ... needs checking
   \begingroup
     \usefloatcaptionstyleandcolor\c!style\c!color
     \clf_doifelselisthastitle{\currentfloat}\numexpr\currentfloatnumber\relax
       \donothing
       \emptyfloatcaptiontrue
     \ifnofloatnumber
     \else
       \floatcaptionparameter\c!headcommand % <- nieuw
         {\usefloatcaptionstyleandcolor\c!headstyle\c!headcolor\thecurrentfloatnumber}%
       \ifnofloatcaption \else \ifemptyfloatcaption \else
         \doifelsenothing{\floatcaptionparameter\c!spaceinbetween}
           {\floatcaptionparameter\c!headseparator\relax
            \scratchskip\floatcaptionparameter\c!distance\relax
            \dotfskip\scratchskip\emergencystretch.5\scratchskip}
           {\blank[\floatcaptionparameter\c!spaceinbetween]}%
       \fi \fi
     \fi
     \ifnofloatcaption
       \global\d_strc_floats_caption_height\zeropoint
       \global\d_strc_floats_caption_depth \zeropoint
     \else
       \usefloatcaptionstyleandcolor\c!textstyle\c!textcolor
       \global\d_strc_floats_caption_height\strutheight
       \global\d_strc_floats_caption_depth \strutdepth
       \thecurrentfloatcaption\endgraf
     \fi
   \endgroup
   \strc_floats_make_complete_caption_after
   \doifsomething{\floatcaptionparameter\c!spaceafter}{\blank[\floatcaptionparameter\c!spaceafter]}}

\protect

\define[1]\hanginghead{\llap{\hbox to 5em{#1\hss}}}

\setupcaption
  [figure]
  [width=\dimexpr\textwidth-5em\relax,
   headcommand=\hanginghead,
   distance=0pt]

\starttext

\startplacefigure[title={\samplefile{knuth}}]
  \externalfigure[cow]
\stopplacefigure

\stoptext