Added margins and padding to Grid and a test program to make sure they're the same...

grid.go

@@ -134,16 +134,19 @@ func (g *Grid) allocate(x int, y int, width int, height int, d *sysSizeData) (al
 
 	var current *allocation		// for neighboring
 
+	// TODO return if nControls == 0?
 	// before we do anything, steal the margin so nested Stacks/Grids don't double down
 	xmargin := d.xmargin
 	ymargin := d.ymargin
 	d.xmargin = 0
 	d.ymargin = 0
-	// 0) inset the available rect by the margins
+	// 0) inset the available rect by the margins and needed padding
 	x += xmargin
 	y += ymargin
 	width -= xmargin * 2
 	height -= ymargin * 2
+	width -= (len(g.colwidths) - 1) * d.xpadding
+	height -= (len(g.rowheights) - 1) * d.ypadding
 	// 1) clear data structures
 	for i := range g.rowheights {
 		g.rowheights[i] = 0
@@ -197,15 +200,16 @@ func (g *Grid) allocate(x int, y int, width int, height int, d *sysSizeData) (al
 				current = nil			// spaces don't have allocation data
 			}
 			allocations = append(allocations, as...)
-			x += g.colwidths[col]
+			x += g.colwidths[col] + d.xpadding
 		}
 		x = startx
-		y += g.rowheights[row]
+		y += g.rowheights[row] + d.ypadding
 	}
 	return
 }
 
 // filling and stretchy are ignored for preferred size calculation
+// We don't consider the margins here, but will need to if Window.SizeToFit() is ever made a thing.
 func (g *Grid) preferredSize(d *sysSizeData) (width int, height int) {
 	max := func(a int, b int) int {
 		if a > b {
@@ -214,6 +218,8 @@ func (g *Grid) preferredSize(d *sysSizeData) (width int, height int) {
 		return b
 	}
 
+	width -= (len(g.colwidths) - 1) * d.xpadding
+	height -= (len(g.rowheights) - 1) * d.ypadding
 	// 1) clear data structures
 	for i := range g.rowheights {
 		g.rowheights[i] = 0

test/main.go

@@ -280,6 +280,10 @@ var labelAlignTest = flag.Bool("label", false, "show Label Alignment test window
 var spacingTest = flag.Bool("spacing", false, "margins and padding on Window")
 
 func myMain() {
+	if *spacetest != "" {
+		spaceTest()
+		return
+	}
 	if *doArea {
 		areaTest()
 		return

test/spacing.go

@@ -0,0 +1,54 @@
+// 26 june 2014
+package main
+
+import (
+	"flag"
+	"image"
+	"image/color"
+	"image/draw"
+	. "github.com/andlabs/ui"
+)
+
+// spacing test
+
+type solidColor struct {
+	c	color.Color
+}
+func (s solidColor) Paint(r image.Rectangle) *image.RGBA {
+	i := image.NewRGBA(r)
+	draw.Draw(i, r, &image.Uniform{s.c}, image.ZP, draw.Src)
+	return i
+}
+func (s solidColor) Mouse(m MouseEvent) bool { return false }
+func (s solidColor) Key(e KeyEvent) bool { return false }
+
+var spacetest = flag.String("spacetest", "", "test space idempotency; arg is x or y; overrides -area")
+func spaceTest() {
+	w := 100
+	h := 50
+	ng := 1
+	gsx, gsy := 1, 0
+	f := NewVerticalStack
+	if *spacetest == "x" {
+		w = 50
+		h = 100
+		ng = 2
+		gsx, gsy = 0, 1
+		f = NewHorizontalStack
+	}
+	ah := solidColor{color.NRGBA{0,0,255,255}}
+	a1 := NewArea(w, h, ah)
+	a2 := NewArea(w, h, ah)
+	a3 := NewArea(w, h, ah)
+	a4 := NewArea(w, h, ah)
+	win := NewWindow("Stack", 250, 250)
+	win.SetSpaced(true)
+	win.Open(f(a1, a2))
+	win = NewWindow("Grid", 250, 250)
+	win.SetSpaced(true)
+	g := NewGrid(ng, a3, a4)
+	g.SetFilling(0, 0)
+	g.SetStretchy(gsx, gsy)
+	win.Open(g)
+	select {}
+}