I was trying to merge table's cell in a Powerpoint document and found nothing in the API. Searching on the net, I only found out that it's was simply not implemented.

http://apache-poi.1045710.n5.nabble.com/HSLF-merging-tablecells-possible-td2294865.html

I made a quick patch in the XSLFTableCell class to expose the 'gridSpan', 'rowSpan', 'hMerge' and 'vMerge' attributes of the "tc" element (the table cell node in the OOXML schema) and added a method in the XSLFTable class to merge the desired cells :
  public void mergeCells(int firstRow, int lastRow, int firstCol, int lastCol);

In the client code :

   XSLFTable table = newSlide.createTable();
   ...
   XSLFTableRow row = table.addRow();
   ....
   table.mergeCells(0, 1, 0, 1);

Note : You need the full OOXML-schemas jar file (16 MB) to make the (Powerpoint) table work in POI.  The lite version don't seem to work for me.

Due to project rush I only implemented what I need and didn't review side effect s or alternative uses (exemple : merge all the cell in the table, unmerge cells, etc ?)