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>

ui/app/os_macos.go

@@ -15,7 +15,6 @@ import (
 	"errors"
 	"image"
 	"runtime"
-	"sync"
 	"time"
 	"unsafe"
 
@@ -36,13 +35,15 @@ type window struct {
 	stage Stage
 }
 
-// Only support one main window for now.
-var singleWindow struct {
-	mu      sync.Mutex
-	hasOpts bool
-	opts    WindowOptions
+type windowError struct {
+	window *Window
+	err    error
 }
 
+var windowOpts = make(chan WindowOptions)
+
+var windows = make(chan windowError)
+
 var viewFactory func() uintptr
 
 var views = make(map[C.CFTypeRef]*window)
@@ -162,7 +163,6 @@ func gio_onTerminate(view C.CFTypeRef) {
 	w := views[view]
 	delete(views, view)
 	w.setStage(StageDead)
-	close(windows)
 }
 
 //export gio_onHide
@@ -185,28 +185,23 @@ func gio_onCreate(view C.CFTypeRef) {
 	ow := newWindow(w)
 	w.w = ow
 	views[view] = w
-	windows <- ow
+	windows <- windowError{window: ow}
 }
 
-func createWindow(opts WindowOptions) error {
-	singleWindow.mu.Lock()
-	defer singleWindow.mu.Unlock()
-	if singleWindow.hasOpts {
-		panic("only one window supported")
-	}
-	singleWindow.opts = opts
-	singleWindow.hasOpts = true
-	return nil
+func createWindow(opts WindowOptions) (*Window, error) {
+	windowOpts <- opts
+	werr := <-windows
+	return werr.window, werr.err
 }
 
 func Main() {
 	view := C.CFTypeRef(viewFactory())
 	if view == 0 {
-		// TODO: return this error from CreateWindow.
-		panic(errors.New("CreateWindow: failed to create view"))
+		windows <- windowError{err: errors.New("CreateWindow: failed to create view")}
+		return
 	}
 	cfg := getConfig()
-	opts := singleWindow.opts
+	opts := <-windowOpts
 	w := cfg.Pixels(opts.Width)
 	h := cfg.Pixels(opts.Height)
 	title := C.CString(opts.Title)