ui/app,apps/gophers,apps/hello: replace CreateWindow with NewWindow

Gio doesn't support multiple windows anyway, so get rid of the
app.Windows channel and use NewWindow call for the mobile platforms
as well.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

apps/hello/hello.go

@@ -18,26 +18,10 @@ import (
 )
 
 func main() {
-	err := app.CreateWindow(app.WindowOptions{
-		Width:  ui.Dp(400),
-		Height: ui.Dp(800),
-		Title:  "Hello World",
-	})
-	if err != nil {
-		log.Fatal(err)
-	}
 	app.Main()
 }
 
 func init() {
-	go func() {
-		for w := range app.Windows() {
-			go loop(w)
-		}
-	}()
-}
-
-func loop(w *app.Window) {
 	regular, err := sfnt.Parse(goregular.TTF)
 	if err != nil {
 		panic("failed to load font")
@@ -45,19 +29,29 @@ func loop(w *app.Window) {
 	var faces measure.Faces
 	black := &image.Uniform{color.Black}
 	face := faces.For(regular, ui.Dp(50))
-	for w.IsAlive() {
-		e := <-w.Events()
-		switch e := e.(type) {
-		case app.Draw:
-			faces.Cfg = e.Config
-			cs := layout.ExactConstraints(w.Size())
-			root, _ := (text.Label{Src: black, Face: face, Text: "Hello, World!"}).Layout(cs)
-			w.Draw(root)
-			faces.Frame()
+	go func() {
+		w, err := app.NewWindow(app.WindowOptions{
+			Width:  ui.Dp(400),
+			Height: ui.Dp(800),
+			Title:  "Hello World",
+		})
+		if err != nil {
+			log.Fatal(err)
 		}
-		w.Ack()
-	}
-	if w.Err() != nil {
-		log.Fatal(err)
-	}
+		for w.IsAlive() {
+			e := <-w.Events()
+			switch e := e.(type) {
+			case app.Draw:
+				faces.Cfg = e.Config
+				cs := layout.ExactConstraints(w.Size())
+				root, _ := (text.Label{Src: black, Face: face, Text: "Hello, World!"}).Layout(cs)
+				w.Draw(root)
+				faces.Frame()
+			}
+			w.Ack()
+		}
+		if w.Err() != nil {
+			log.Fatal(err)
+		}
+	}()
 }