indentAmount property for tabledrag is buggy

Confirmed that this bug still exists in 7.x-dev (so should be fixed there first and then backported).

The bug is not limited to just the book module, but rears its head anytime you have a draggable table with 0 rows. The current code in tabledrag.js does not correctly handle empty tables (it performs actions on the first draggable row, without ensuring it exists):

  if (this.indentEnabled) {
    this.indentCount = 1; // Total width of indents, set in makeDraggable.
    // Find the width of indentations to measure mouse movements against.
    // Because the table doesn't need to start with any indentations, we
    // manually append 2 indentations in the first draggable row, measure
    // the offset, then remove.
    var indent = Drupal.theme('tableDragIndentation');
    var testCell = $('tr.draggable:first td:first', table).prepend(indent).prepend(indent);
    this.indentAmount = $('.indentation', testCell).get(1).offsetLeft - $('.indentation', testCell).get(0).offsetLeft;
    $('.indentation', testCell).slice(0, 2).remove();
  }

One option might be to create an extra row in the table with the draggable class (and visiblity set to hidden), determine the indentAmount using that row, and then removing it again?

That was my first thought, but there is the off chance that rows are added dynamically to a table later on, which made me wonder if it wouldn't be better to come up with a safer way of determining indentAmount, instead of skipping it when no rows are present...

Don't know enough about this to determine the right course of action though...

I am also having this issue with Drupal 6.x.

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The bug went away for me when I turn off Devel Themer module. Changed title as this is most likely a collision of contrib and core, not just book. I found the bug on /admin/content/node-type/page/fields

Josh

Patch #8 doesn't work for 6.x for me, disabling Devel Themer helped.

same error with Drupal 6.x, d I've solved disabling Theme Devel module

Disabling the "Themer Info" solved the problem (I don't mean unchecking the checkbox but choosing "Disable Theme developer" in the Development block.

There seems to be a conflict between the handles and the themer info.

This is what IE said :
get(...).offsetLeft' is null or not an object

This is the case in Drupal 6.14

Same here hopefully, devel will fix it soon.

Related issue: #663068: $(".indentation", testCell).get(1) is undefined

DRUPAL 6
Ok, but being the problem void row, I just removed it in Drupal.tableDrag function, before anything else:

$('> tbody > tr.draggable, > tr.draggable', table)
.filter(function(index) {return $("td", this).length == 0;}).remove();

but I think this should be solved in table generation in cck/theme/content-admin-field-overview-form.tpl.php

I added a default case in switch to print

it print:
stdClass Object ( [weight] => [parent] => [hidden_name] => [label_class] => label- [row_type] => [indentation] => [class] => draggable )

... somewhere someway this kind of row are added, and is not a perfect behavior
check if this is the case for drupal 7

I believe this is a duplicate of #737596: tabledrag.js: $(".indentation", testCell).get(1) is undefined, which has been fixed.