Returns the list of RenderBox objects that are in the given column, in row order, starting from the first row.
This is a lazily-evaluated iterable.
Source
Iterable<RenderBox> column(int x) sync* {
for (int y = 0; y < rows; y += 1) {
final int xy = x + y * columns;
RenderBox child = _children[xy];
if (child != null)
yield child;
}
}