ui/app,apps/gophers,apps/hello: revert NewWindow to CreateWindow

It turns out we already support multiple windows on Android: when
the activity is recreated.

This reverts commit f21b5eb1df.

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

apps/hello/hello.go

@@ -20,14 +20,24 @@ import (
 )
 
 func main() {
-	// Never called on mobile, blocks forever on
-	// desktop.
+	err := app.CreateWindow(nil)
+	if err != nil {
+		log.Fatal(err)
+	}
 	app.Main()
 }
 
 // On iOS and Android main will never be called, so
 // setting up the window must run in an init function.
 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")
@@ -35,26 +45,18 @@ func init() {
 	var faces measure.Faces
 	black := &image.Uniform{color.Black}
 	face := faces.For(regular, ui.Dp(50))
-	// On iOS and Android app.NewWindow blocks, waiting
-	// for the platform to create a window.
-	go func() {
-		w, err := app.NewWindow(nil)
-		if 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()
 		}
-		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()
-			}
-		}
-		if w.Err() != nil {
-			log.Fatal(err)
-		}
-	}()
+	}
+	if w.Err() != nil {
+		log.Fatal(err)
+	}
 }