Autolayout Table Sizing Algorithm

The layout algorithm for the incremental display mode has already been presented in a previous section. If the COLS attribute is missing from the table start tag, then the user agent should use the autolayout sizing algorithm, which uses two passes through the table data.

In the first pass, word wrapping is disabled, and the user agent keeps track of the minimum and maximum width of each cell. The maximum width is given by the widest line. As word wrap has been disabled, paragraphs are treated as long lines unless broken by <BR> elements. The minimum width is given by the widest word or image etc. taking into account leading indents and list bullets etc. In other words, if you were to format the cell's content in a window of its own, determine the minimum width you could make the window before things begin to be clipped.

The minimum and maximum cell widths are then used to determine the corresponding minimum and maximum widths for the columns. These in turn, are used to find the minimum and maximum width for the table. Note that cells can contain nested tables, but this doesn't complicate the code significantly. The next step is to assign column widths according to the current window size (more accurately - the width between the left and right margins).

The table borders and intercell margins need to be included in the assignment step. There are three cases:

1. The minimum table width is equal to or wider than the available space. In this case, assign the minimum widths and allow the user to scroll horizontally. For conversion to braille, it will be necessary to replace the cells by references to notes containing their full content. By convention these appear before the table.
2. The maximum table width fits within the available space. In this case, set the columns to their maximum widths.
3. The maximum width of the table is greater than the available space, but the minimum table width is smaller. In this case, find the difference between the available space and the minimum table width, lets call it W. Lets also call D the difference between maximum and minimum width of the table.

   For each column, let d be the the difference between maximum and minimum width of that column. Now set the column's width to the minimum width plus d times W over D. This makes columns with lots of text wider than columns with smaller amounts.

This assignment step is then repeated for nested tables. In this case, the width of the enclosing table's cell plays the role of the current window size in the above description. This process is repeated recursively for all nested tables.

If the table width is specified with the WIDTH attribute, the user agent attempts to set column widths to match. The WIDTH attribute should be disregarded if this results in columns having less than their minimum widths.

If relative widths are specified with the COLW element, the algorithm is modified to increase column widths over the minimum width to meet the relative width constraints.