ui/app: create windows directly

Replace CreateWindow with NewWindow that immediately creates a Window
ready to use.

Drop the Windows channel of windows created by the system. For iOS
and Android where the system creates the windows, let them rendezvous
with the window created in the first NewWindow call.

Android is further changed so that destroying and re-creating the
Java Activity simply reconnects with the original Window.

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

ui/app/os_macos.go

@@ -15,7 +15,6 @@ import (
 	"errors"
 	"image"
 	"runtime"
-	"sync"
 	"time"
 	"unsafe"
 
@@ -35,12 +34,7 @@ type window struct {
 	stage Stage
 }
 
-// Only support one main window for now.
-var singleWindow struct {
-	mu      sync.Mutex
-	hasOpts bool
-	opts    *WindowOptions
-}
+var mainWindow = newWindowRendezvous()
 
 var viewFactory func() C.CFTypeRef
 
@@ -170,7 +164,6 @@ func gio_onTerminate(view C.CFTypeRef) {
 	w := views[view]
 	delete(views, view)
 	w.setStage(StageDead)
-	close(windows)
 }
 
 //export gio_onHide
@@ -190,31 +183,26 @@ func gio_onCreate(view C.CFTypeRef) {
 	w := &window{
 		view: view,
 	}
-	ow := newWindow(w)
-	w.w = ow
+	wopts := <-mainWindow.out
+	w.w = wopts.window
+	w.w.setDriver(w)
 	views[view] = w
-	windows <- 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(win *Window, opts *WindowOptions) error {
+	mainWindow.in <- windowAndOptions{win, opts}
+	return <-mainWindow.errs
 }
 
 func Main() {
+	wopts := <-mainWindow.out
 	view := viewFactory()
 	if view == 0 {
 		// TODO: return this error from CreateWindow.
 		panic(errors.New("CreateWindow: failed to create view"))
 	}
 	cfg := getConfig()
-	opts := singleWindow.opts
+	opts := wopts.opts
 	w := cfg.Px(opts.Width)
 	h := cfg.Px(opts.Height)
 	title := C.CString(opts.Title)