Background

Set up zebra striping using extreme tables. The ConTeXt tables are generated by converting an ASCII Markdown table via pandoc.

Minimum Example

starttext
 startplacetable
 startxtable
 startxtablehead[head]
 startxrow
 startxcell Item stopxcell
 startxcell[align=left] Cost ($) stopxcell
 startxcell[align=left] Description stopxcell
 stopxrow
 stopxtablehead
 startxtablebody[body]
 dorecurse4
 startxrow
 startxcell Item stopxcell
 startxcell[align=left] 100 stopxcell
 startxcell[align=left] Cow text stopxcell
 stopxrow
 
 stopxtablebody
 startxtablefoot[foot]
 startxrow
 startxcell bf Total stopxcell
 startxcell[align=left] bf 400 stopxcell
 startxcell[align=left] stopxcell
 stopxrow
 stopxtablefoot
 stopxtable
 stopplacetable
stoptext

Problem

ConTeXt, which is rather consistent with its setup macros, does not appear to define a setupxrow or setupxcell. I had anticipated something like:

definecolor[lime][r=0.75, g=1, b=0] 
definecolor[transparentred][r=1,t=.5,a=1]
setupxrow[odd][background=lime]
setupxrow[even][background=transparentred]

This did not compile.

Question

Without using definextable to create a custom xtable definition, how would you apply zebra striping so that every other non-header row has a coloured background?

With natural tables this would have been easy because the environment let you set different values for even and odd rows.

startsetups [tablebackground]
 setupTABLE [row] [odd] [background=color,backgroundcolor=gray]
stopsetups

starttext

bTABLE[setups=tablebackground]
dorecurse9bTR expandedbTD Row recurselevel eTD eTR
eTABLE

stoptext

Extreme tables on the other hand don’t support this kind of setup and you have to use the overlay mechanism to create your own backgrounds for the cells.

In the overlay setting you can check the value of the currentxtablerow counter to apply a different command for odd and even rows.

startuseMPgraphic tablebackground
 fill OverlayBox withcolor MPcolorgray ;
stopuseMPgraphic

defineoverlay
 [tablebackground]
 [ifoddcurrentxtablerow
 useMPgraphictablebackground%
 fi]

starttext

startxtable[background=tablebackground]
dorecurse9startxrow expandedstartxcell Row recurselevel stopxcell stopxrow
stopxtable

stoptext

To skip the table header:

defineoverlay
 [tablebackground]
 [ifnumcurrentxtablerow>1
 ifoddcurrentxtablerowuseMPgraphictablebackgroundfi
 fi]

To apply shading against even rows:

startuseMPgraphic tablebackground
 fill OverlayBox withcolor MPcolorgray ;
stopuseMPgraphic

defineoverlay
 [tablebackground]
 [ifnumcurrentxtablerow>1
 ifoddcurrentxtablerow else
 useMPgraphictablebackground%
 fi
 fi]

setupxtable[background=tablebackground]

To apply the background against all tables in the document, use:

setupxtable[background=tablebackground]