While working a bug, I came across something very interesting in regard to a DataGrid's horizontalScrollPolicy. This was the bug: A DataGrid had a few columns, some with specific widths. Oddly though, the width properties seemed to be ignored, and the columns widths were sized in odd proportions. They weren't evenly spaced as you'd expect if the width was totally ignored. It seemed like the width was just picked at random because they made no sense.
I tracked it down to the horizontalScrollPolicy of the DataGrid.
The horizontalScrollPolicy is significant because when the policy is set to ‘off’, individual DataGridColumn widths are ignored. This prevents you from setting the width of a column, and having the rest proportional. To set specific column widths, you must set the policy to ‘auto’ or ‘on’. It you set it to ‘on’, the scrollbar is shown even if one is not needed. Setting the policy to ‘auto’ will show/hide the scrollbar if needed.
I think that this would have been an important point to address in the ASDocs. I should also point out that this was in reference to the 3.5 SDK. Perhaps 4.x is different.
