Added a way to let Controls in a Grid be sized to fill their cells.

grid.go

@@ -7,15 +7,18 @@ import (
 )
 
 // A Grid arranges Controls in a two-dimensional grid.
-// All Controls in a Grid maintain their preferred sizes.
 // The height of each row and the width of each column is the maximum preferred height and width (respectively) of all the controls in that row or column (respectively).
 // Controls are aligned to the top left corner of each cell.
+// All Controls in a Grid maintain their preferred sizes by default; if a Control is marked as being "filling", it will be sized to fill its cell.
+// Even if a Control is marked as filling, its preferred size is used to calculate cell sizes.
+// All cooridnates in a Grid are given in (row,column) form with (0,0) being the top-left cell.
 // Unlike other UI toolkit Grids, this Grid does not (yet? TODO) allow Controls to span multiple rows or columns.
 // TODO differnet row/column control alignment; stretchy controls or other resizing options
 type Grid struct {
 	lock					sync.Mutex
 	created				bool
 	controls				[][]Control
+	filling				[][]bool
 	widths, heights			[][]int		// caches to avoid reallocating each time
 	rowheights, colwidths	[]int
 }
@@ -34,11 +37,13 @@ func NewGrid(nPerRow int, controls ...Control) *Grid {
 	}
 	nRows := len(controls) / nPerRow
 	cc := make([][]Control, nRows)
+	cf := make([][]bool, nRows)
 	cw := make([][]int, nRows)
 	ch := make([][]int, nRows)
 	i := 0
 	for row := 0; row < nRows; row++ {
 		cc[row] = make([]Control, nPerRow)
+		cf[row] = make([]bool, nPerRow)
 		cw[row] = make([]int, nPerRow)
 		ch[row] = make([]int, nPerRow)
 		for x := 0; x < nPerRow; x++ {
@@ -48,6 +53,7 @@ func NewGrid(nPerRow int, controls ...Control) *Grid {
 	}
 	return &Grid{
 		controls:		cc,
+		filling:		cf,
 		widths:		cw,
 		heights:		ch,
 		rowheights:	make([]int, nRows),
@@ -55,6 +61,18 @@ func NewGrid(nPerRow int, controls ...Control) *Grid {
 	}
 }
 
+// SetFilling sets the given control of the Grid as filling its cell instead of staying at its preferred size.
+// This function cannot be called after the Window that contains the Grid has been created.
+func (g *Grid) SetFilling(row int, column int) {
+	g.lock.Lock()
+	defer g.lock.Unlock()
+
+	if g.created {
+		panic("Grid.SetFilling() called after window create")		// TODO
+	}
+	g.filling[row][column] = true
+}
+
 func (g *Grid) make(window *sysData) error {
 	g.lock.Lock()
 	defer g.lock.Unlock()
@@ -106,7 +124,13 @@ func (g *Grid) setRect(x int, y int, width int, height int) error {
 	startx := x
 	for row, xcol := range g.controls {
 		for col, c := range xcol {
-			err := c.setRect(x, y, g.widths[row][col], g.heights[row][col])
+			w := g.widths[row][col]
+			h := g.heights[row][col]
+			if g.filling[row][col] {
+				w = g.colwidths[col]
+				h = g.rowheights[row]
+			}
+			err := c.setRect(x, y, w, h)
 			if err != nil {
 				return fmt.Errorf("error setting size of control (%d,%d) in Grid.setRect(): %v", row, col, err)
 			}

main_test.go

@@ -20,6 +20,7 @@ func gridWindow() (*Window, error) {
 		b00, b01, b02,
 		Space(), l11, b12,
 		l20, c21, l22)
+	g.SetFilling(1, 2)
 	return w, w.Open(g)
 }