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/gophers/main.go

@@ -121,6 +121,14 @@ func main() {
 		fmt.Println("The quota for anonymous GitHub API access is very low. Specify a token with -token to avoid quota errors.")
 		fmt.Println("See https://help.github.com/en/articles/creating-a-personal-access-token-for-the-command-line.")
 	}
+	err := app.CreateWindow(&app.WindowOptions{
+		Width:  ui.Dp(400),
+		Height: ui.Dp(800),
+		Title:  "Gophers",
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
 	app.Main()
 }
 
@@ -141,16 +149,13 @@ func init() {
 	fonts.italic = mustLoadFont(goitalic.TTF)
 	fonts.mono = mustLoadFont(gomono.TTF)
 	go func() {
-		w, err := app.NewWindow(&app.WindowOptions{
-			Width:  ui.Dp(400),
-			Height: ui.Dp(800),
-			Title:  "Gophers",
-		})
-		if err != nil {
-			log.Fatal(err)
-		}
-		if err := newApp(w).run(); err != nil {
-			log.Fatal(err)
+		for w := range app.Windows() {
+			w := w
+			go func() {
+				if err := newApp(w).run(); err != nil {
+					log.Fatal(err)
+				}
+			}()
 		}
 	}()
 }

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)
+	}
 }

ui/app/app.go

@@ -59,12 +59,13 @@ const (
 // Set it with the go tool linker flag -X.
 var extraArgs string
 
-// NewWindow creates a new window for a set of window
+var windows = make(chan *Window)
+
+// CreateWindow creates a new window for a set of window
 // options. The options are hints; the platform is free to
 // ignore or adjust them.
-// If the current program is running on iOS and Android,
-// NewWindow the window previously created by the platform.
-func NewWindow(opts *WindowOptions) (*Window, error) {
+// CreateWindow is not supported on iOS and Android.
+func CreateWindow(opts *WindowOptions) error {
 	if opts == nil {
 		opts = &WindowOptions{
 			Width:  ui.Dp(800),
@@ -78,6 +79,10 @@ func NewWindow(opts *WindowOptions) (*Window, error) {
 	return createWindow(opts)
 }
 
+func Windows() <-chan *Window {
+	return windows
+}
+
 func (l Stage) String() string {
 	switch l {
 	case StageDead:

ui/app/os_android.go

@@ -55,8 +55,6 @@ type window struct {
 
 var theJVM *C.JavaVM
 
-var windows = make(chan *Window)
-
 var views = make(map[C.jlong]*window)
 
 func jniGetMethodID(env *C.JNIEnv, class C.jclass, method, sig string) C.jmethodID {
@@ -381,6 +379,6 @@ func Main() {
 	panic("unreachable")
 }
 
-func createWindow(opts *WindowOptions) (*Window, error) {
-	return <-windows, nil
+func createWindow(opts *WindowOptions) error {
+	return errors.New("createWindow not supported")
 }

ui/app/os_ios.go

@@ -42,8 +42,6 @@ var layerFactory func() uintptr
 
 var views = make(map[C.CFTypeRef]*window)
 
-var windows = make(chan *Window)
-
 func init() {
 	// Darwin requires UI operations happen on the main thread only.
 	runtime.LockOSThread()
@@ -235,8 +233,8 @@ func (w *window) setTextInput(s key.TextInputState) {
 	}
 }
 
-func createWindow(opts *WindowOptions) (*Window, error) {
-	return <-windows, nil
+func createWindow(opts *WindowOptions) error {
+	panic("unsupported")
 }
 
 func Main() {

ui/app/os_macos.go

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

ui/app/os_wayland.go

@@ -141,28 +141,30 @@ func Main() {
 	<-mainDone
 }
 
-func createWindow(opts *WindowOptions) (*Window, error) {
+func createWindow(opts *WindowOptions) error {
 	connMu.Lock()
 	defer connMu.Unlock()
 	if len(winMap) > 0 {
 		panic("multiple windows are not supported")
 	}
 	if err := waylandConnect(); err != nil {
-		return nil, err
+		return err
 	}
 	w, err := createNativeWindow(opts)
 	if err != nil {
 		conn.destroy()
-		return nil, err
+		return err
 	}
 	go func() {
+		windows <- w.w
 		w.setStage(StageVisible)
 		w.loop()
 		w.destroy()
 		conn.destroy()
+		close(windows)
 		close(mainDone)
 	}()
-	return w.w, nil
+	return nil
 }
 
 func createNativeWindow(opts *WindowOptions) (*window, error) {

ui/app/os_windows.go

@@ -157,37 +157,34 @@ func Main() {
 	<-mainDone
 }
 
-func createWindow(opts *WindowOptions) (*Window, error) {
+func createWindow(opts *WindowOptions) error {
 	onceMu.Lock()
 	defer onceMu.Unlock()
 	if len(winMap) > 0 {
 		panic("multiple windows are not supported")
 	}
-	type windowError struct {
-		window *Window
-		err    error
-	}
-	cerr := make(chan windowError)
+	cerr := make(chan error)
 	go func() {
 		// Call win32 API from a single OS thread.
 		runtime.LockOSThread()
 		w, err := createNativeWindow(opts)
 		if err != nil {
-			cerr <- windowError{err: err}
+			cerr <- err
 			return
 		}
 		defer w.destroy()
-		cerr <- windowError{w.w, nil}
+		cerr <- nil
+		windows <- w.w
 		showWindow(w.hwnd, _SW_SHOWDEFAULT)
 		setForegroundWindow(w.hwnd)
 		setFocus(w.hwnd)
 		if err := w.loop(); err != nil {
 			panic(err)
 		}
+		close(windows)
 		close(mainDone)
 	}()
-	werr := <-cerr
-	return werr.window, werr.err
+	return <-cerr
 }
 
 func createNativeWindow(opts *WindowOptions) (*window, error) {

ui/app/window.go

@@ -36,7 +36,6 @@ type Window struct {
 	mu           sync.Mutex
 	stage        Stage
 	size         image.Point
-	skipAcks     int
 	syncGPU      bool
 	animating    bool
 	hasNextFrame bool
@@ -208,9 +207,11 @@ func (w *Window) event(e Event) {
 	case key.Event:
 		needRedraw = true
 	case ChangeStage:
-		needAck = true
 		w.stage = e.Stage
-		w.syncGPU = true
+		if w.stage > StageDead {
+			needAck = true
+			w.syncGPU = true
+		}
 	case Draw:
 		if e.Size == (image.Point{}) {
 			panic(errors.New("internal error: zero-sized Draw"))
@@ -223,9 +224,6 @@ func (w *Window) event(e Event) {
 		w.syncGPU = e.sync
 		w.size = e.Size
 	}
-	if !needAck {
-		w.skipAcks++
-	}
 	stage := w.stage
 	w.mu.Unlock()
 	if needRedraw {