JavaScripting InDesign

They say that necessity is the mother of invention. Yesterday I was faced with needing to know the exact location of the top of a cell in a table so I could precisely position an anchored object. The x-coordinate of the cell was no problem because this table filled the column from side to side, so my anchored rectangle was easy to position horizontally, but vertically is another thing entirely.

It's worth stepping back a bit to explain what I was trying to achieve. I had two documents each with a huge table in it, over 300 rows and 7 or 8 columns. I wanted to have alternating fills but I could use the regular table features because the fills needed to be transparent so that the complex background could still be seen.

I conceived of the idea of putting an exactly sized rectangle over every other row by inserting it as an anchored item in the first character position of the first cell of each affected row. This would allow the "fill" to be transparent without the rest of the table also having to be transparent. It was the work of a moment to create the necessary object style to apply the fill and transparency and to set up the anchored object settings. But the heights of the rows vary and so the offset from the baseline of the text also needed to be calculated for each row. Here's the function I constructed to do that:

  function sizeAndPostionRect(table, row, rect) {
    row.cells[0].texts[0].recompose();
    var width = table.width;
    var height = row.cells[0].height;
    var myBounds = rect.geometricBounds;
    myBounds[0] = myBounds[2] - height;
    myBounds[3] = myBounds[1] + width;
    rect.geometricBounds = myBounds;
    var myCell = row.cells[0];
    var tI = myCell.topInset
    var fB = myCell.firstBaselineOffset;
    myCell.firstBaselineOffset = FirstBaseline.fixedHeight;
    myCell.minimumFirstBaselineOffset = 0;
    myCell.verticalJustification = VerticalJustification.topAlign;
    var myCellTop = myCell.texts[0].characters[1].baseline - tI;
    myCell.verticalJustification = VerticalJustification.centerAlign
    myCell.firstBaselineOffset = fB;
    rect.anchoredObjectSettings.anchorYoffset = myCellTop - myCell.texts[0].characters[1].baseline;
  }

The trick is to maneuver the baseline of the text in the cell so it sits on the top edge of the cell, then having grabbed the value, put everything back the way it was.