Does anyone know why an object would miss a property?

Question

We have a script that export our Indesign documents to HTML and one of the routine is to export tables. In this script we go throught each Tables->Rows->Cells and evaluate some of the properties (i.e. bottomEdgeStrokeType, topEdgeStrokeType, etc...) and transport them to HTML.

Now yesterday we had problem converting one particular document because some cells were missing the "bottomEdgeStrokeType" property entirely. I've discovered this by outputting the properties of each cells and compare the faulty ones with the others.

This line bellow was trowing the error: "Invalid object for this request.".

var cellType = cell["bottomEdgeStrokeType"];

Now, to fix this I've wrapped this around a try catch block to handle the case when it's not there, but now what is puzzling me is how on earth can Extendscript instantiate an object with missing properties?

Indesign version: CS5.5

Answer 1

A property is not only 'undefined' if it cannot exist at all (such as asking for the parent text frame for a character in overset text), but InDesign's Javascript engine also fails to return a reasonably accurate result for multiple values.

If you ask for "the" point size of a paragraph, where this paragraph contains multiple sizes, poor ID does not consider to return something like CONSTANT.Mixed, or the first value only, or (what I might have preferred) an array of the values; it returns undefined instead.

So how can a single table cell have multiple bottom strokes? If the cell underneath it is split into multiple cells, and one has a "top" stroke but the other has not.

It's difficult to recommend an adequate solution. You could first test if the current cell is "merged" (as far as InDesign's internal table model is concerned) with columnSpan; and if so, iterate over the number of columns spanned and test the next row's cells for their top stroke, which in theory should match the bottom stroke of the cell above. (I find myself wondering if this is always true. ID's table model is ... weird. It's not entirely like a HTML table, despite the functional overlaps.)

If columnSpan is greater than 1 and equal to the number of cells immediately below the current one, you could test if all of their "top" values are the same and if so use that value. (I never tested this so ID's table model may simply fail because a cell is merged, regardless of same-values or not.)

One could attempt to flag this cell's next row to output "top" strokes as well -- but alternating top and bottom strokes may not align nicely in CSS, side to side. Perhaps it's best to translate only the first top stroke value to "the" bottom stroke property for your current cell, and fix up manually where needed (how?) or, a reasonable action, hope that no-one will ever notice it.