Introduce new layouts.Grid construct

layouts/grid.go

@@ -18,12 +18,18 @@ type Grid struct {
 // will contract. Boxes are laid out left to right, then top to bottom. Boxes
 // that go beyond the lengh of rows will be laid out according to columns, but
 // they will not expand vertically.
-func NewGrid (columns, rows []bool) *Grid {
-	this := &Grid {
-		xExpand: columns,
-		yExpand: rows,
+//
+// If you aren't sure how to use this constructor, here is an example:
+//
+//            X0     X1    X2     Y0    Y1    Y2
+//   NewGrid(true, false, true)(false, true, true)
+func NewGrid (columns ...bool) func (rows ...bool) *Grid {
+	return func (rows ...bool) *Grid {
+		return &Grid {
+			xExpand: columns,
+			yExpand: rows,
+		}
 	}
-	return this
 }
 
 func (this *Grid) MinimumSize (hints tomo.LayoutHints, boxes []tomo.Box) image.Point {