[css-grid] IE fragmentation algorithm

Section 12 for the CSS grid spec is currently empty and I was asked to document IE's algorithm for fragmenting grids. It consists of a small modification to the regular (non-fragmented) algorithm: 

First, compute grid track sizes and grid item positions as if the grid is being laid out in unconstrained space.

Since fragmenting a grid item can increase its size, if a "content-sized row" is broken across fragments, increase its size as needed in the subsequent fragment so that it remains large enough to contain fragmented items that span only that row.  For the purposes of this heuristic a "content-sized row" is a row with a content min track sizing function or a fraction row in an auto height grid.

Other row sizes are not recomputed following the adjustment.

Note that this algorithm can easily cause unnecessary overflow.  For example, if the fragmentation heuristic comes into effect anywhere in a fixed height grid with a fraction row the rows are guaranteed to overflow the grid.

Peter

Received on Thursday, 29 August 2013 22:42:21 UTC