4 files changed, 103 insertions, 13 deletions
diff --git a/layout/layout.go b/layout/doc.go
index b04aa35..bae4673 100644
--- a/layout/layout.go
+++ b/layout/doc.go
@@ -13,16 +13,3 @@ Draw calls from the children are intercepted and translated onto their
 respective areas before being forwarded to the parent Env.
 */
 package layout
-
-import (
-	"image"
-	"image/color"
-	"image/draw"
-)
-
-func drawBackground(c color.Color) func(draw.Image) image.Rectangle {
-	return func(img draw.Image) image.Rectangle {
-		draw.Draw(img, img.Bounds(), &image.Uniform{c}, image.ZP, draw.Src)
-		return img.Bounds()
-	}
-}
diff --git a/layout/subimage.go b/layout/draw.go
index ecbe931..760a149 100644
--- a/layout/subimage.go
+++ b/layout/draw.go
@@ -2,9 +2,11 @@ package layout
 
 import (
 	"image"
+	"image/color"
 	"image/draw"
 )
 
+// subimager is implemented by most Image types.
 type subimager interface {
 	SubImage(image.Rectangle) image.Image
 }
@@ -15,3 +17,11 @@ type subimager interface {
 func subimage(m draw.Image, r image.Rectangle) draw.Image {
 	return m.(subimager).SubImage(r).(draw.Image)
 }
+
+// drawBackground returns a draw call that fills the entire image with a color.
+func drawBackground(c color.Color) func(draw.Image) image.Rectangle {
+	return func(img draw.Image) image.Rectangle {
+		draw.Draw(img, img.Bounds(), &image.Uniform{c}, image.ZP, draw.Src)
+		return img.Bounds()
+	}
+}
diff --git a/layout/resize.go b/layout/resize.go
new file mode 100644
index 0000000..1d3d6f1
--- /dev/null
+++ b/layout/resize.go
@@ -0,0 +1,35 @@
+package layout
+
+import "image"
+
+// ResizeAll resizes a layout to consume all of its parent's area.
+func ResizeAll(r image.Rectangle) image.Rectangle { return r }
+
+// ResizeQuad1 resizes a layout to consume the top-right quadrant of its parent.
+func ResizeQuad1(r image.Rectangle) image.Rectangle {
+	mid := midpoint(r)
+	return image.Rect(mid.X, r.Min.Y, r.Max.X, mid.Y)
+}
+
+// ResizeQuad2 resizes a layout to consume the top-left quadrant of its parent.
+func ResizeQuad2(r image.Rectangle) image.Rectangle {
+	mid := midpoint(r)
+	return image.Rectangle{r.Min, mid}
+}
+
+// ResizeQuad3 resizes a layout to consume the bottom-left quadrant of its parent.
+func ResizeQuad3(r image.Rectangle) image.Rectangle {
+	mid := midpoint(r)
+	return image.Rect(r.Min.X, mid.Y, mid.X, r.Max.Y)
+}
+
+// ResizeQuad4 resizes a layout to consume the bottom-right quadrant of its parent.
+func ResizeQuad4(r image.Rectangle) image.Rectangle {
+	mid := midpoint(r)
+	return image.Rectangle{mid, r.Max}
+}
+
+// midpoint returns the point in the middle of a rectangle.
+func midpoint(r image.Rectangle) image.Point {
+	return r.Min.Add(r.Max).Div(2)
+}
diff --git a/layout/resize_test.go b/layout/resize_test.go
new file mode 100644
index 0000000..5be7a41
--- /dev/null
+++ b/layout/resize_test.go
@@ -0,0 +1,58 @@
+package layout_test
+
+import (
+	"image"
+	"testing"
+
+	"github.com/faiface/gui/layout"
+)
+
+func TestResizeAll(t *testing.T) {
+	t.Parallel()
+	parent := image.Rect(111, 222, 333, 444)
+	child := layout.ResizeAll(parent)
+	want := parent
+	if child != want {
+		t.Errorf("got %v; want %v", child, want)
+	}
+}
+
+func TestResizeQuad1(t *testing.T) {
+	t.Parallel()
+	parent := image.Rect(111, 222, 333, 444)
+	child := layout.ResizeQuad1(parent)
+	want := image.Rect(222, 222, 333, 333)
+	if child != want {
+		t.Errorf("got %v; want %v", child, want)
+	}
+}
+
+func TestResizeQuad2(t *testing.T) {
+	t.Parallel()
+	parent := image.Rect(111, 222, 333, 444)
+	child := layout.ResizeQuad2(parent)
+	want := image.Rect(111, 222, 222, 333)
+	if child != want {
+		t.Errorf("got %v; want %v", child, want)
+	}
+}
+
+func TestResizeQuad3(t *testing.T) {
+	t.Parallel()
+	parent := image.Rect(111, 222, 333, 444)
+	child := layout.ResizeQuad3(parent)
+	want := image.Rect(111, 333, 222, 444)
+	if child != want {
+		t.Errorf("got %v; want %v", child, want)
+	}
+}
+
+func TestResizeQuad4(t *testing.T) {
+	t.Parallel()
+	parent := image.Rect(111, 222, 333, 444)
+	child := layout.ResizeQuad4(parent)
+	want := image.Rect(222, 333, 333, 444)
+	if child != want {
+		t.Errorf("got %v; want %v", child, want)
+	}
+}