app{,/internal/window}: make app.Main blocking on desktop platforms

This CL implements the app.Main function as a blocking-forever function
for JS, Wayland, Windows and X11.
This works better for applications that can now programmatically close
windows.

app/app.go

@@ -35,8 +35,10 @@ func DataDir() (string, error) {
 	return dataDir()
 }
 
-// Main must be called from the program main function. It
-// blocks until there are no more windows active.
+// Main must be called last from the program main function.
+// On most platforms Main blocks forever, for Android and
+// iOS it returns immediately to give control of the main
+// thread back to the system.
 //
 // Calling Main is necessary because some operating systems
 // require control of the main thread of the program for

app/internal/window/os_js.go

@@ -36,8 +36,6 @@ type window struct {
 	animating bool
 }
 
-var mainDone = make(chan struct{})
-
 func NewWindow(win Callbacks, opts *Options) error {
 	doc := js.Global().Get("document")
 	cont := getContainer(doc)
@@ -70,7 +68,6 @@ func NewWindow(win Callbacks, opts *Options) error {
 		w.draw(true)
 		select {}
 		w.cleanup()
-		close(mainDone)
 	}()
 	return nil
 }
@@ -449,7 +446,7 @@ func (w *window) config() (int, int, float32, unit.Metric) {
 }
 
 func Main() {
-	<-mainDone
+	select {}
 }
 
 func translateKey(k string) (string, bool) {

app/internal/window/os_macos.go

@@ -40,7 +40,6 @@ __attribute__ ((visibility ("hidden"))) CGFloat gio_getScreenBackingScale(void);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_readClipboard(void);
 __attribute__ ((visibility ("hidden"))) void gio_writeClipboard(unichar *chars, NSUInteger length);
 __attribute__ ((visibility ("hidden"))) void gio_setNeedsDisplay(CFTypeRef viewRef);
-__attribute__ ((visibility ("hidden"))) void gio_appTerminate(void);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createWindow(CFTypeRef viewRef, const char *title, CGFloat width, CGFloat height, CGFloat minWidth, CGFloat minHeight, CGFloat maxWidth, CGFloat maxHeight);
 __attribute__ ((visibility ("hidden"))) void gio_makeKeyAndOrderFront(CFTypeRef windowRef);
 __attribute__ ((visibility ("hidden"))) NSPoint gio_cascadeTopLeftFromPoint(CFTypeRef windowRef, NSPoint topLeft);
@@ -271,9 +270,6 @@ func gio_onClose(view C.CFTypeRef) {
 	w.view = 0
 	C.CFRelease(w.window)
 	w.window = 0
-	if len(viewMap) == 0 {
-		C.gio_appTerminate()
-	}
 }
 
 //export gio_onHide

app/internal/window/os_macos.m

@@ -153,12 +153,6 @@ CFTypeRef gio_createWindow(CFTypeRef viewRef, const char *title, CGFloat width,
 	}
 }
 
-void gio_appTerminate(void) {
-	@autoreleasepool {
-		[NSApp terminate:nil];
-	}
-}
-
 void gio_close(CFTypeRef windowRef) {
   NSWindow* window = (__bridge NSWindow *)windowRef;
   [window performClose:nil];

app/internal/window/os_unix.go

@@ -8,16 +8,8 @@ import (
 	"errors"
 )
 
-// windowCounter keeps track of the number of windows.
-// A send of +1 or -1 represents a change in window count.
-var windowCounter = make(chan int)
-
 func Main() {
-	// Wait for first window
-	count := <-windowCounter
-	for count > 0 {
-		count += <-windowCounter
-	}
+	select {}
 }
 
 // instead of creating files with build tags for each combination of wayland +/- x11

app/internal/window/os_wayland.go

@@ -232,14 +232,8 @@ func newWLWindow(window Callbacks, opts *Options) error {
 		d.destroy()
 		return err
 	}
-	// Increment window counter.
-	windowCounter <- +1
 	w.w = window
 	go func() {
-		defer func() {
-			// Decrement window counter.
-			windowCounter <- -1
-		}()
 		defer d.destroy()
 		defer w.destroy()
 		w.w.SetDriver(w)

app/internal/window/os_windows.go

@@ -57,10 +57,6 @@ type window struct {
 
 const _WM_REDRAW = windows.WM_USER + 0
 
-// windowCounter keeps track of the number of windows.
-// A send of +1 or -1 represents a change in window count.
-var windowCounter = make(chan int)
-
 type gpuAPI struct {
 	priority    int
 	initializer func(w *window) (Context, error)
@@ -84,11 +80,7 @@ var resources struct {
 }
 
 func Main() {
-	// Wait for first window
-	count := <-windowCounter
-	for count > 0 {
-		count += <-windowCounter
-	}
+	select {}
 }
 
 func NewWindow(window Callbacks, opts *Options) error {
@@ -104,11 +96,7 @@ func NewWindow(window Callbacks, opts *Options) error {
 		defer w.destroy()
 		cerr <- nil
 		winMap.Store(w.hwnd, w)
-		windowCounter <- +1
-		defer func() {
-			winMap.Delete(w.hwnd)
-			windowCounter <- -1
-		}()
+		defer winMap.Delete(w.hwnd)
 		w.w = window
 		w.w.SetDriver(w)
 		defer w.w.Event(system.DestroyEvent{})

app/internal/window/os_x11.go

@@ -576,12 +576,7 @@ func newX11Window(gioWin Callbacks, opts *Options) error {
 	// make the window visible on the screen
 	C.XMapWindow(dpy, win)
 
-	// Increment window counter.
-	windowCounter <- +1
 	go func() {
-		defer func() {
-			windowCounter <- -1
-		}()
 		w.w.SetDriver(w)
 		w.setStage(system.StageRunning)
 		w.loop()