layout: add background color option

6 files changed, 97 insertions, 35 deletions

diff --git a/color.go b/color.go
new file mode 100644
index 0000000..e2b9bc1
--- /dev/null
+++ b/color.go
@@ -0,0 +1,12 @@
+package gui
+
+import (
+	"fmt"
+	"image/color"
+)
+
+func HexToColor(hex string) color.Color {
+	var r, g, b uint8
+	fmt.Sscanf(hex, "#%2X%2X%2X", &r, &g, &b)
+	return color.RGBA{r, g, b, 255}
+}
diff --git a/examples/pexeso/main.go b/examples/pexeso/main.go
index 56bd6e6..7be7baa 100644
--- a/examples/pexeso/main.go
+++ b/examples/pexeso/main.go
@@ -1,7 +1,6 @@
 package main
 
 import (
-	"fmt"
 	"image"
 	"image/color"
 	"image/draw"
@@ -19,31 +18,25 @@ func EqualColors(c1, c2 color.Color) bool {
 	return r1 == r2 && g1 == g2 && b1 == b2 && a1 == a2
 }
 
-func HexToColor(hex string) color.Color {
-	var r, g, b uint8
-	fmt.Sscanf(hex, "#%2X%2X%2X", &r, &g, &b)
-	return color.RGBA{r, g, b, 255}
-}
-
 var Colors = []color.Color{
-	HexToColor("#E53935"),
-	HexToColor("#F06292"),
-	HexToColor("#9C27B0"),
-	HexToColor("#673AB7"),
-	HexToColor("#3F51B5"),
-	HexToColor("#2196F3"),
-	HexToColor("#29B6F6"),
-	HexToColor("#00BCD4"),
-	HexToColor("#009688"),
-	HexToColor("#4CAF50"),
-	HexToColor("#8BC34A"),
-	HexToColor("#CDDC39"),
-	HexToColor("#FFEB3B"),
-	HexToColor("#FFC107"),
-	HexToColor("#FF9800"),
-	HexToColor("#8D6E63"),
-	HexToColor("#9E9E9E"),
-	HexToColor("#607D8B"),
+	gui.HexToColor("#E53935"),
+	gui.HexToColor("#F06292"),
+	gui.HexToColor("#9C27B0"),
+	gui.HexToColor("#673AB7"),
+	gui.HexToColor("#3F51B5"),
+	gui.HexToColor("#2196F3"),
+	gui.HexToColor("#29B6F6"),
+	gui.HexToColor("#00BCD4"),
+	gui.HexToColor("#009688"),
+	gui.HexToColor("#4CAF50"),
+	gui.HexToColor("#8BC34A"),
+	gui.HexToColor("#CDDC39"),
+	gui.HexToColor("#FFEB3B"),
+	gui.HexToColor("#FFC107"),
+	gui.HexToColor("#FF9800"),
+	gui.HexToColor("#8D6E63"),
+	gui.HexToColor("#9E9E9E"),
+	gui.HexToColor("#607D8B"),
 }
 
 type PairMsg struct {
@@ -59,7 +52,7 @@ func Tile(env gui.Env, pair chan PairMsg, r image.Rectangle, clr color.Color) {
 			bottomR.Min.Y = bottomR.Max.Y - coveredY
 			topR := r
 			topR.Max.Y = bottomR.Min.Y
-			draw.Draw(drw, bottomR, &image.Uniform{HexToColor("#37474F")}, image.ZP, draw.Src)
+			draw.Draw(drw, bottomR, &image.Uniform{gui.HexToColor("#37474F")}, image.ZP, draw.Src)
 			draw.Draw(drw, topR, &image.Uniform{clr}, image.ZP, draw.Src)
 			return r
 		}
@@ -124,7 +117,7 @@ func run() {
 
 	env.Draw() <- func(drw draw.Image) image.Rectangle {
 		r := image.Rect(0, 0, 600, 600)
-		draw.Draw(drw, r, &image.Uniform{HexToColor("#CFD8DC")}, image.ZP, draw.Src)
+		draw.Draw(drw, r, &image.Uniform{gui.HexToColor("#CFD8DC")}, image.ZP, draw.Src)
 		return r
 	}
 
diff --git a/layout/doc.go b/layout/layout.go
index bae4673..b04aa35 100644
--- a/layout/doc.go
+++ b/layout/layout.go
@@ -13,3 +13,16 @@ 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/options.go b/layout/options.go
new file mode 100644
index 0000000..2ea0c81
--- /dev/null
+++ b/layout/options.go
@@ -0,0 +1,34 @@
+package layout
+
+import (
+	"image/color"
+)
+
+var (
+	defaultBg = color.Transparent
+)
+
+// Option is a function option for layout constructors.
+type Option func(*options)
+
+type options struct {
+	bg color.Color // background color
+}
+
+// Background sets the background color of a layout.
+func Background(bg color.Color) Option {
+	return func(o *options) {
+		o.bg = bg
+	}
+}
+
+// EvalOptions evaluates a list of option functions, returning the final set.
+func evalOptions(o ...Option) options {
+	opts := options{
+		bg: defaultBg,
+	}
+	for i := range o {
+		o[i](&opts)
+	}
+	return opts
+}
diff --git a/layout/region.go b/layout/region.go
index 1e92455..4e3a791 100644
--- a/layout/region.go
+++ b/layout/region.go
@@ -15,7 +15,9 @@ type Region struct {
 
 // NewRegion creates a region layout that occupies part of the parent env's area, as determined by the resize function.
 // Resize takes the area of the parent and returns the area of the region.
-func NewRegion(env gui.Env, resize func(image.Rectangle) image.Rectangle) gui.Env {
+func NewRegion(env gui.Env, resize func(image.Rectangle) image.Rectangle, o ...Option) gui.Env {
+	opts := evalOptions(o...)
+
 	events := make(chan gui.Event)                     // to child
 	drw := make(chan func(draw.Image) image.Rectangle) // from child
 
@@ -25,17 +27,20 @@ func NewRegion(env gui.Env, resize func(image.Rectangle) image.Rectangle) gui.En
 		area := resize(event.(gui.Resize).Rectangle) // first event guaranteed to be Resize
 		events <- gui.Resize{area}
 
+		env.Draw() <- drawBackground(opts.bg)
+
 		for {
 			select {
-			case event := <-env.Events():
+			case event := <-env.Events(): // event from parent
 				switch event := event.(type) {
 				case gui.Resize:
+					env.Draw() <- drawBackground(opts.bg)
 					area = resize(event.Rectangle)
-					events <- gui.Resize{area}
+					events <- gui.Resize{area} // forward to child
 				default:
 					events <- event
 				}
-			case f, ok := <-drw:
+			case f, ok := <-drw: // draw call from child
 				if !ok {
 					close(events)
 					close(env.Draw())
diff --git a/test/region.go b/test/region.go
index afd739e..0b99a3a 100644
--- a/test/region.go
+++ b/test/region.go
@@ -11,6 +11,10 @@ import (
 	"github.com/faiface/mainthread"
 )
 
+var (
+	bg = gui.HexToColor("#999999") // background color
+)
+
 func main() {
 	mainthread.Run(run)
 }
@@ -24,9 +28,10 @@ func run() {
 	mux, env := gui.NewMux(w)
 
 	// Create region in bottom-right quadrant of window
-	region := layout.NewRegion(mux.MakeEnv(), func(r image.Rectangle) image.Rectangle {
+	resize := func(r image.Rectangle) image.Rectangle {
 		return image.Rect(r.Min.X+r.Dx()/2, r.Min.Y+r.Dy()/2, r.Max.X, r.Max.Y)
-	})
+	}
+	region := layout.NewRegion(mux.MakeEnv(), resize, layout.Background(bg))
 	go blinker(region)
 
 	for event := range env.Events() {
@@ -64,9 +69,9 @@ func blinker(env gui.Env) {
 				go func() {
 					for i := 0; i < 3; i++ {
 						env.Draw() <- redraw(false)
-						time.Sleep(time.Second / 3)
+						time.Sleep(time.Second / 6)
 						env.Draw() <- redraw(true)
-						time.Sleep(time.Second / 3)
+						time.Sleep(time.Second / 6)
 					}
 				}()
 			}