the empty quarter

The technique for alternate row styling described in a previous post is applicable for tables with detail rows (a detail row in a table corresponds to a row in the bound data set). However, it is often the case that the table does not contain any detail rows at all and instead displays only aggregated data, i.e. header or footer rows of a group.

In such scenario the row.__rownum value cannot be used, because __rownum is incremented for each row in the data set, meaning its value will depend on how many rows are being aggregated into the summary row.

Instead, the highlight logic can be defined using a variable incremented on each summary row.

1. First, initialize the variable. This can be done e.g. in the onCreate method of a label in the static column header.
   
   reportContext.setPersistentGlobalVariable( "aggRowNum", "0" );

2. In an object on the summary row (either a label, aggreation or the row itself) the following code is placed in the onCreate method to increment the value of the variable (the funny stuff is to force explicit conversion between string and number and back):
   
   var n = reportContext.getPersistentGlobalVariable( "aggRowNum" );
   n = (n*1) + 1;
   reportContext.setPersistentGlobalVariable( "aggRowNum", "" + n );

3. Finally, the highlight property of the row is set as follows:
   
   reportContext.getPersistentGlobalVariable( "aggRowNum" ) % 2; | equal to | 1