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Re: Problem with JAWS Table Navigation?

for

From: Jared Smith
Date: Dec 2, 2009 4:33PM

On Wed, Dec 2, 2009 at 2:25 PM, Don Mauck wrote:
> And it seems to contradict the rules they gave us a little over 1 year ago for determining a data table:
>
> 1. it has at least 2 valid data rrows
> 1.1 a valid data row contains at minimum 2 columns
> 1.2. at least 4 cells in the table fall within a given size (between 200 and 16000 square
> pixels)
> 2.1 if the attribute datatable=TRUE or datatable=1 its a data table.

Where did you get these 'rules'? I've never seen them before. Any
additional details?

Actually, these rules are accurate, I think. I'll try to explain this
as best as I can - it's a bit mind blowing.

- JAWS analyzes the size of the table cells, not the amount of text
within the cell (though these are naturally related). 16000 square
pixels (this isn't very big - a couple short sentences of default text
or a small 200X80 pixel image) is the threshold. I'll call anything
bigger than this, a "big" cell.

- A cell can be "big" even if it has one character with a very large
margin or padding.

- A cell can be "big" (>16000 square pixels) because the contents of
another cell in its row or column is tall or wide. An empty cell can
be "big". It has nothing to do with the contents or markup of the cell
- only its dimensions.

- If any cell within the table is "big", JAWS thinks it's a layout
table, regardless of whether table headers or any other data table
markup is applied. However, if there are at least 4 cells within that
table that are NOT "big", then it thinks it's a data table - even if
no data table markup is applied. So looking at the original poster's
example - the three cells in the first column are NOT big, but all
three cells in the 2nd column ARE big because the large amounts of
text in one of those cells (which makes the other two cells wide
enough to pass the threshold). This results in only 3 small cells,
thus JAWS treats it as a layout table.

- If no cell is big, then it's always a data table so long as there
are at least 2 row and 2 columns - again, regardless of presence or
absence of table headers.

I can understand the need for some heuristics for better handling
tables that are not coded with accessibility in mind, but no screen
reader should EVER treat a table with proper header markup as a layout
table - especially because a cell just happens to be big. Likewise, a
layout table should not be treated as a data table, just because more
than 3 cells happen to be small.

For those that don't understand, this is a significant issue because
screen readers treat layout and data tables significantly different.
Layout tables are essentially ignored and read as flat content. Data
tables are identified and can be navigated.

Jared Smith
WebAIM