app: [API] remove Main

All platforms already allow the omission of the call to Main and running
Windows on the main goroutine. This change just gets rid of Main, and
documents the special requirement on Window.Event.

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

app/app.go

@@ -120,18 +120,6 @@ func DataDir() (string, error) {
 	return dataDir()
 }
 
-// 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
-// running windows.
-func Main() {
-	osMain()
-}
-
 func (FrameEvent) ImplementsEvent() {}
 
 func init() {

app/doc.go

@@ -33,28 +33,12 @@ For example:
 A program must keep receiving events from the event channel until
 [DestroyEvent] is received.
 
-# Main
+# Main Thread
 
-The Main function must be called from a program's main function, to hand over
+Some GUI platform need access to the main thread of the program. To avoid a
-control of the main thread to operating systems that need it.
+deadlock on such platforms, at least one Window must have its Event method
-
+called by the main goroutine. It doesn't have to be any particular Window;
-Because Main is also blocking on some platforms, the event loop of a Window must run in a goroutine.
+even a destroyed Window suffices.
-
-For example, to display a blank but otherwise functional window:
-
-	package main
-
-	import "gioui.org/app"
-
-	func main() {
-		go func() {
-			w := app.NewWindow()
-			for {
-				w.Event()
-			}
-		}()
-		app.Main()
-	}
 
 # Permissions
 

app/metal_darwin.go

@@ -60,8 +60,9 @@ static void presentDrawable(CFTypeRef queueRef, CFTypeRef drawableRef) {
 		id<MTLDrawable> drawable = (__bridge id<MTLDrawable>)drawableRef;
 		id<MTLCommandQueue> queue = (__bridge id<MTLCommandQueue>)queueRef;
 		id<MTLCommandBuffer> cmdBuffer = [queue commandBuffer];
-		[cmdBuffer presentDrawable:drawable];
 		[cmdBuffer commit];
+		[cmdBuffer waitUntilScheduled];
+		[drawable present];
 	}
 }
 

app/metal_ios.go

@@ -21,7 +21,10 @@ Class gio_layerClass(void) {
 static CFTypeRef getMetalLayer(CFTypeRef viewRef) {
 	@autoreleasepool {
 		UIView *view = (__bridge UIView *)viewRef;
-		return CFBridgingRetain(view.layer);
+		CAMetalLayer *l = (CAMetalLayer *)view.layer;
+		l.needsDisplayOnBoundsChange = YES;
+		l.presentsWithTransaction = YES;
+		return CFBridgingRetain(l);
 	}
 }
 

app/metal_macos.go

@@ -14,7 +14,11 @@ package app
 
 CALayer *gio_layerFactory(void) {
 	@autoreleasepool {
-		return [CAMetalLayer layer];
+		CAMetalLayer *l = [CAMetalLayer layer];
+		l.autoresizingMask = kCALayerHeightSizable|kCALayerWidthSizable;
+		l.needsDisplayOnBoundsChange = YES;
+		l.presentsWithTransaction = YES;
+		return l;
 	}
 }
 

app/os.go

@@ -45,6 +45,8 @@ type Config struct {
 	CustomRenderer bool
 	// Decorated reports whether window decorations are provided automatically.
 	Decorated bool
+	// Focused reports whether has the keyboard focus.
+	Focused bool
 	// decoHeight is the height of the fallback decoration for platforms such
 	// as Wayland that may need fallback client-side decorations.
 	decoHeight unit.Dp

app/os_android.go

@@ -593,7 +593,8 @@ func Java_org_gioui_GioView_onBack(env *C.JNIEnv, class C.jclass, view C.jlong)
 //export Java_org_gioui_GioView_onFocusChange
 func Java_org_gioui_GioView_onFocusChange(env *C.JNIEnv, class C.jclass, view C.jlong, focus C.jboolean) {
 	w := cgo.Handle(view).Value().(*window)
-	w.processEvent(key.FocusEvent{Focus: focus == C.JNI_TRUE})
+	w.config.Focused = focus == C.JNI_TRUE
+	w.processEvent(ConfigEvent{Config: w.config})
 }
 
 //export Java_org_gioui_GioView_onWindowInsets
@@ -1316,9 +1317,6 @@ func findClass(env *C.JNIEnv, name string) C.jclass {
 	return C.jni_FindClass(env, cn)
 }
 
-func osMain() {
-}
-
 func newWindow(window *callbacks, options []Option) {
 	mainWindow.in <- windowAndConfig{window, options}
 	<-mainWindow.windows

app/os_darwin.go

@@ -15,8 +15,8 @@ __attribute__ ((visibility ("hidden"))) void gio_hideCursor();
 __attribute__ ((visibility ("hidden"))) void gio_showCursor();
 __attribute__ ((visibility ("hidden"))) void gio_setCursor(NSUInteger curID);
 
-static bool isMainThread() {
+static int isMainThread() {
-	return [NSThread isMainThread];
+	return [NSThread isMainThread] ? 1 : 0;
 }
 
 static NSUInteger nsstringLength(CFTypeRef cstr) {
@@ -77,7 +77,7 @@ var mainFuncs = make(chan func(), 1)
 
 // runOnMain runs the function on the main thread.
 func runOnMain(f func()) {
-	if C.isMainThread() {
+	if isMainThread() {
 		f()
 		return
 	}
@@ -87,6 +87,10 @@ func runOnMain(f func()) {
 	}()
 }
 
+func isMainThread() bool {
+	return C.isMainThread() != 0
+}
+
 //export gio_dispatchMainFuncs
 func gio_dispatchMainFuncs() {
 	for {
@@ -259,10 +263,3 @@ func windowSetCursor(from, to pointer.Cursor) pointer.Cursor {
 	C.gio_setCursor(C.NSUInteger(macosCursorID[to]))
 	return to
 }
-
-func (w *window) wakeup() {
-	runOnMain(func() {
-		w.loop.Wakeup()
-		w.loop.FlushEvents()
-	})
-}

app/os_darwin.m

@@ -1,11 +0,0 @@
-// SPDX-License-Identifier: Unlicense OR MIT
-
-#import <Foundation/Foundation.h>
-
-#include "_cgo_export.h"
-
-void gio_wakeupMainThread(void) {
-	dispatch_async(dispatch_get_main_queue(), ^{
-		gio_dispatchMainFuncs();
-	});
-}

app/os_ios.go

@@ -211,7 +211,8 @@ func onDestroy(h C.uintptr_t) {
 //export onFocus
 func onFocus(h C.uintptr_t, focus int) {
 	w := viewFor(h)
-	w.ProcessEvent(key.FocusEvent{Focus: focus != 0})
+	w.config.Focused = focus != 0
+	w.ProcessEvent(ConfigEvent{Config: w.config})
 }
 
 //export onLowMemory
@@ -387,13 +388,17 @@ func newWindow(win *callbacks, options []Option) {
 	<-mainWindow.windows
 }
 
-func osMain() {
-}
-
 //export gio_runMain
 func gio_runMain() {
 	runMain()
 }
 
+func (w *window) wakeup() {
+	runOnMain(func() {
+		w.loop.Wakeup()
+		w.loop.FlushEvents()
+	})
+}
+
 func (UIKitViewEvent) implementsViewEvent() {}
 func (UIKitViewEvent) ImplementsEvent()     {}

app/os_ios.m

@@ -276,3 +276,9 @@ void gio_viewSetHandle(CFTypeRef viewRef, uintptr_t handle) {
 	GioView *v = (__bridge GioView *)viewRef;
 	v.handle = handle;
 }
+
+void gio_wakeupMainThread(void) {
+	dispatch_async(dispatch_get_main_queue(), ^{
+		gio_dispatchMainFuncs();
+	});
+}

app/os_js.go

@@ -258,11 +258,13 @@ func (w *window) addEventListeners() {
 		return nil
 	})
 	w.addEventListener(w.tarea, "focus", func(this js.Value, args []js.Value) interface{} {
-		w.processEvent(key.FocusEvent{Focus: true})
+		w.config.Focused = true
+		w.processEvent(ConfigEvent{Config: w.config})
 		return nil
 	})
 	w.addEventListener(w.tarea, "blur", func(this js.Value, args []js.Value) interface{} {
-		w.processEvent(key.FocusEvent{Focus: false})
+		w.config.Focused = false
+		w.processEvent(ConfigEvent{Config: w.config})
 		w.blur()
 		return nil
 	})
@@ -739,10 +741,6 @@ func (w *window) navigationColor(c color.NRGBA) {
 	theme.Set("content", fmt.Sprintf("#%06X", []uint8{rgba.R, rgba.G, rgba.B}))
 }
 
-func osMain() {
-	select {}
-}
-
 func translateKey(k string) (key.Name, bool) {
 	var n key.Name
 

app/os_macos.go

@@ -39,7 +39,7 @@ import (
 #define MOUSE_DOWN 3
 #define MOUSE_SCROLL 4
 
-__attribute__ ((visibility ("hidden"))) void gio_main(void);
+__attribute__ ((visibility ("hidden"))) void gio_initApp(void);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createView(void);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createWindow(CFTypeRef viewRef, CGFloat width, CGFloat height, CGFloat minWidth, CGFloat minHeight, CGFloat maxWidth, CGFloat maxHeight);
 __attribute__ ((visibility ("hidden"))) void gio_viewSetHandle(CFTypeRef viewRef, uintptr_t handle);
@@ -289,6 +289,16 @@ static void invalidateCharacterCoordinates(CFTypeRef viewRef) {
 		}
 	}
 }
+
+static void dispatchEvent(void) {
+	@autoreleasepool {
+		NSEvent *event = [NSApp nextEventMatchingMask:NSEventMaskAny
+		                                        untilDate:[NSDate distantFuture]
+		                                           inMode:NSDefaultRunLoopMode
+		                                          dequeue:YES];
+		[NSApp sendEvent:event];
+	}
+}
 */
 import "C"
 
@@ -323,13 +333,16 @@ type window struct {
 	config Config
 }
 
-// launched is closed when applicationDidFinishLaunching is called.
+// launched is closed after gio_initApp returns.
 var launched = make(chan struct{})
 
 // nextTopLeft is the offset to use for the next window's call to
 // cascadeTopLeftFromPoint.
 var nextTopLeft C.NSPoint
 
+// mainThreadWindow is the window currently in control of the main thread.
+var mainThreadWindow *window
+
 func windowFor(h C.uintptr_t) *window {
 	return cgo.Handle(h).Value().(*window)
 }
@@ -612,8 +625,9 @@ func gio_onDraw(h C.uintptr_t) {
 //export gio_onFocus
 func gio_onFocus(h C.uintptr_t, focus C.int) {
 	w := windowFor(h)
-	w.ProcessEvent(key.FocusEvent{Focus: focus == 1})
 	w.SetCursor(w.cursor)
+	w.config.Focused = focus == 1
+	w.ProcessEvent(ConfigEvent{Config: w.config})
 }
 
 //export gio_onChangeScreen
@@ -821,23 +835,51 @@ func (w *window) draw() {
 
 func (w *window) ProcessEvent(e event.Event) {
 	w.w.ProcessEvent(e)
-	w.loop.FlushEvents()
+	// The main thread window deliver events in Event.
+	if w != mainThreadWindow {
+		w.loop.FlushEvents()
+	}
 }
 
 func (w *window) Event() event.Event {
-	return w.loop.Event()
+	if !isMainThread() {
+		return w.loop.Event()
+	}
+	mainThreadWindow = w
+	defer func() { mainThreadWindow = nil }()
+	for {
+		if evt, ok := w.loop.win.nextEvent(); ok {
+			return evt
+		}
+		C.dispatchEvent()
+		gio_dispatchMainFuncs()
+	}
 }
 
 func (w *window) Invalidate() {
+	if isMainThread() {
+		mainThreadWindow = w
+		defer func() { mainThreadWindow = nil }()
+	}
 	w.loop.Invalidate()
 }
 
 func (w *window) Run(f func()) {
+	if isMainThread() {
+		mainThreadWindow = w
+		defer func() { mainThreadWindow = nil }()
+	}
 	w.loop.Run(f)
 }
 
 func (w *window) Frame(frame *op.Ops) {
-	w.loop.Frame(frame)
+	if !isMainThread() {
+		w.loop.Frame(frame)
+		return
+	}
+	mainThreadWindow = w
+	defer func() { mainThreadWindow = nil }()
+	w.loop.win.ProcessFrame(frame, nil)
 }
 
 func configFor(scale float32) unit.Metric {
@@ -897,20 +939,27 @@ func gio_onWindowed(h C.uintptr_t) {
 	w.ProcessEvent(ConfigEvent{Config: w.config})
 }
 
-//export gio_onFinishLaunching
-func gio_onFinishLaunching() {
-	close(launched)
-}
-
 func newWindow(win *callbacks, options []Option) {
-	<-launched
+	w := &window{
-	res := make(chan struct{})
+		redraw: make(chan struct{}, 1),
-	runOnMain(func() {
+		w:      win,
-		w := &window{
+	}
-			redraw: make(chan struct{}, 1),
+	w.loop = newEventLoop(w.w, w.wakeup)
-			w:      win,
+	if isMainThread() {
+		mainThreadWindow = w
+		defer func() { mainThreadWindow = nil }()
+		select {
+		case <-launched:
+		default:
+			// If we're the main thread, initialize the GUI.
+			C.gio_initApp()
+			close(launched)
 		}
-		w.loop = newEventLoop(w.w, w.wakeup)
+	} else {
+		<-launched
+	}
+	res := make(chan struct{}, 1)
+	runOnMain(func() {
 		win.SetDriver(w)
 		res <- struct{}{}
 		if err := w.init(); err != nil {
@@ -963,10 +1012,6 @@ func (w *window) init() error {
 	return nil
 }
 
-func osMain() {
-	C.gio_main()
-}
-
 func convertKey(k rune) (key.Name, bool) {
 	var n key.Name
 	switch k {
@@ -1051,5 +1096,14 @@ func convertMods(mods C.NSUInteger) key.Modifiers {
 	return kmods
 }
 
+func (w *window) wakeup() {
+	runOnMain(func() {
+		w.loop.Wakeup()
+		if w != mainThreadWindow {
+			w.loop.FlushEvents()
+		}
+	})
+}
+
 func (AppKitViewEvent) implementsViewEvent() {}
 func (AppKitViewEvent) ImplementsEvent()     {}

app/os_macos.m

@@ -69,6 +69,212 @@ static void handleMouse(GioView *view, NSEvent *event, int typ, CGFloat dx, CGFl
 	gio_onMouse(view.handle, (__bridge CFTypeRef)event, typ, event.buttonNumber, p.x, height - p.y, dx, dy, [event timestamp], [event modifierFlags]);
 }
 
+@interface GioApplication: NSApplication
+@end
+
+// Variables for tracking resizes.
+static struct {
+	NSPoint dir;
+	NSEvent *lastMouseDown;
+	NSPoint off;
+} resizeState = {};
+
+static NSBitmapImageRep *nsImageBitmap(NSImage *img) {
+	NSArray<NSImageRep *> *reps = img.representations;
+	if ([reps count] == 0) {
+		return nil;
+	}
+	NSImageRep *rep = reps[0];
+	if (![rep isKindOfClass:[NSBitmapImageRep class]]) {
+		return nil;
+	}
+	return (NSBitmapImageRep *)rep;
+}
+
+static NSCursor *lookupPrivateNSCursor(SEL name) {
+	if (![NSCursor respondsToSelector:name]) {
+		return nil;
+	}
+	id obj = [NSCursor performSelector:name];
+	if (![obj isKindOfClass:[NSCursor class]]) {
+		return nil;
+	}
+	return (NSCursor *)obj;
+}
+
+static BOOL isEqualNSCursor(NSCursor *c1, SEL name2) {
+	NSCursor *c2 = lookupPrivateNSCursor(name2);
+	if (c2 == nil || !NSEqualPoints(c1.hotSpot, c2.hotSpot)) {
+		return NO;
+	}
+	NSImage *img1 = c1.image;
+	NSImage *img2 = c2.image;
+	if (!NSEqualSizes(img1.size, img2.size)) {
+		return NO;
+	}
+	NSBitmapImageRep *bit1 = nsImageBitmap(img1);
+	NSBitmapImageRep *bit2 = nsImageBitmap(img2);
+	if (bit1 == nil || bit2 == nil) {
+		return NO;
+	}
+	NSInteger n1 = bit1.numberOfPlanes*bit1.bytesPerPlane;
+	NSInteger n2 = bit1.numberOfPlanes*bit1.bytesPerPlane;
+	if (n1 != n2) {
+		return NO;
+	}
+	if (memcmp(bit1.bitmapData, bit2.bitmapData, n1) != 0) {
+		return NO;
+	}
+	return YES;
+}
+
+@implementation GioApplication
+- (NSEvent *)nextEventMatchingMask:(NSEventMask)mask
+                         untilDate:(NSDate *)expiration
+                            inMode:(NSRunLoopMode)mode
+                           dequeue:(BOOL)deqFlag {
+	if ([mode isEqualToString:NSEventTrackingRunLoopMode]) {
+		NSEvent *l = resizeState.lastMouseDown;
+		if (l != nil) {
+			//lastMouseDown = nil;
+			NSCursor *cur = [NSCursor currentSystemCursor];
+			NSPoint dir = {};
+			NSPoint off = {};
+			NSSize wsz = [l window].frame.size;
+			NSPoint center = NSMakePoint(wsz.width/2, wsz.height/2);
+			NSPoint p = [l locationInWindow];
+			if (p.x >= center.x) {
+				dir.x = 1;
+				off.x = p.x - wsz.width;
+			} else {
+				dir.x = -1;
+				off.x = p.x;
+			}
+			if (p.y >= center.y) {
+				dir.y = 1;
+				off.y = p.y - wsz.height;
+			} else {
+				dir.y = -1;
+				off.y = p.y;
+			}
+			// The button down coordinate distinguish the four quadrants. Use the
+			// cursor image to determine the precise direction.
+			SEL nw = @selector(_windowResizeNorthWestCursor);
+			SEL n = @selector(_windowResizeNorthCursor);
+			SEL ne = @selector(_windowResizeNorthEastCursor);
+			SEL e = @selector(_windowResizeEastCursor);
+			SEL se = @selector(_windowResizeSouthEastCursor);
+			SEL s = @selector(_windowResizeSouthCursor);
+			SEL sw = @selector(_windowResizeSouthWestCursor);
+			SEL w = @selector(_windowResizeWestCursor);
+			SEL ns = @selector(_windowResizeNorthSouthCursor);
+			SEL ew = @selector(_windowResizeEastWestCursor);
+			SEL nwse = @selector(_windowResizeNorthWestSouthEastCursor);
+			SEL nesw = @selector(_windowResizeNorthEastSouthWestCursor);
+			BOOL match = YES;
+			if (dir.x != 0 && (isEqualNSCursor(cur, ew) || isEqualNSCursor(cur, w) || isEqualNSCursor(cur, e))) {
+				dir.y = 0;
+			}
+			if (dir.y != 0 && (isEqualNSCursor(cur, ns) || isEqualNSCursor(cur, s) || isEqualNSCursor(cur, n))) {
+					dir.x = 0;
+			}
+			// If none of the cursors matched, we may deduce that the resize
+			// direction is one of the corners. However, to ensure that at least
+			// one cursor matches, check the corner cursors.
+			if (dir.x == 1 && dir.y == 1) {
+				if (!isEqualNSCursor(cur, nesw) && !isEqualNSCursor(cur, sw)) {
+					dir = NSZeroPoint;
+				}
+			} else if (dir.x == 1 && dir.y == -1) {
+				if (!isEqualNSCursor(cur, nwse) && !isEqualNSCursor(cur, nw)) {
+					dir = NSZeroPoint;
+				}
+			} else if (dir.x == -1 && dir.y == 1) {
+				if (!isEqualNSCursor(cur, nwse) && !isEqualNSCursor(cur, se)) {
+					dir = NSZeroPoint;
+				}
+			} else if (dir.x == -1 && dir.y == -1) {
+				if (!isEqualNSCursor(cur, nesw) && !isEqualNSCursor(cur, ne)) {
+					dir = NSZeroPoint;
+				}
+			}
+			if (!NSEqualPoints(dir, NSZeroPoint)) {
+				NSEvent *cancel = [NSEvent mouseEventWithType:NSEventTypeLeftMouseUp
+											                       location:l.locationInWindow
+											                  modifierFlags:l.modifierFlags
+											                      timestamp:l.timestamp
+											                   windowNumber:l.windowNumber
+											                        context:l.context
+											                    eventNumber:l.eventNumber
+											                     clickCount:l.clickCount
+											                       pressure:l.pressure];
+				resizeState.off = off;
+				resizeState.dir = dir;
+				return cancel;
+			}
+		}
+	}
+	return [super nextEventMatchingMask:mask untilDate:expiration inMode:mode dequeue:deqFlag];
+}
+@end
+
+@interface GioWindow: NSWindow
+@end
+
+@implementation GioWindow
+- (void)sendEvent:(NSEvent *)evt {
+	if (evt.type == NSEventTypeLeftMouseDown) {
+		resizeState.lastMouseDown = evt;
+	}
+	NSPoint dir = resizeState.dir;
+	if (NSEqualPoints(dir, NSZeroPoint)) {
+		[super sendEvent:evt];
+		return;
+	}
+	switch (evt.type) {
+	default:
+		return;
+	case NSEventTypeLeftMouseUp:
+		resizeState.dir = NSZeroPoint;
+		resizeState.lastMouseDown = nil;
+		return;
+	case NSEventTypeLeftMouseDragged:
+		// Ok to proceed.
+		break;
+	}
+	NSPoint loc = evt.locationInWindow;
+	NSPoint off = resizeState.off;
+	loc.x -= off.x;
+	loc.y -= off.y;
+	NSRect frame = [self frame];
+	NSSize min = [self minSize];
+	NSSize max = [self maxSize];
+	CGFloat width = frame.size.width;
+	if (dir.x > 0) {
+		width = loc.x;
+	} else if (dir.x < 0) {
+		width -= loc.x;
+	}
+	width = MIN(max.width, MAX(min.width, width));
+	if (dir.x < 0) {
+		frame.origin.x += frame.size.width - width;
+	}
+	frame.size.width = width;
+	CGFloat height = frame.size.height;
+	if (dir.y > 0) {
+		height = loc.y;
+	} else if (dir.y < 0) {
+		height -= loc.y;
+	}
+	height = MIN(max.height, MAX(min.height, height));
+	if (dir.y < 0) {
+		frame.origin.y += frame.size.height - height;
+	}
+	frame.size.height = height;
+	[self setFrame:frame display:YES animate:NO];
+}
+@end
+
 @implementation GioView
 - (void)setFrameSize:(NSSize)newSize {
 	[super setFrameSize:newSize];
@@ -142,7 +348,6 @@ static void handleMouse(GioView *view, NSEvent *event, int typ, CGFloat dx, CGFl
 	// Don't pass commands up the responder chain.
 	// They will end up in a beep.
 }
-
 - (BOOL)hasMarkedText {
 	int res = gio_hasMarkedText(self.handle);
 	return res ? YES : NO;
@@ -255,14 +460,11 @@ void gio_showCursor() {
 // some cursors are not public, this tries to use a private cursor
 // and uses fallback when the use of private cursor fails.
 static void trySetPrivateCursor(SEL cursorName, NSCursor* fallback) {
-	if ([NSCursor respondsToSelector:cursorName]) {
+	NSCursor *cur = lookupPrivateNSCursor(cursorName);
-		id object = [NSCursor performSelector:cursorName];
+	if (cur == nil) {
-		if ([object isKindOfClass:[NSCursor class]]) {
+		cur = fallback;
-			[(NSCursor*)object set];
-			return;
-		}
 	}
-	[fallback set];
+	[cur set];
 }
 
 void gio_setCursor(NSUInteger curID) {
@@ -361,7 +563,7 @@ CFTypeRef gio_createWindow(CFTypeRef viewRef, CGFloat width, CGFloat height, CGF
 			NSMiniaturizableWindowMask |
 			NSClosableWindowMask;
 
-		NSWindow* window = [[NSWindow alloc] initWithContentRect:rect
+		GioWindow* window = [[GioWindow alloc] initWithContentRect:rect
 													   styleMask:styleMask
 														 backing:NSBackingStoreBuffered
 														   defer:NO];
@@ -410,13 +612,24 @@ void gio_viewSetHandle(CFTypeRef viewRef, uintptr_t handle) {
 - (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
 	[NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
 	[NSApp activateIgnoringOtherApps:YES];
-	gio_onFinishLaunching();
+	// Force the [NSApp run] call to return.
+	[NSApp stop:nil];
+	NSEvent *dummy = [NSEvent otherEventWithType:NSEventTypeApplicationDefined
+	              location:NSZeroPoint
+	         modifierFlags:0
+	             timestamp:0
+	          windowNumber:0
+	               context:nil
+	               subtype:0
+	                 data1:0
+	                 data2:0];
+	[NSApp postEvent:dummy atStart:YES];
 }
 @end
 
-void gio_main() {
+void gio_initApp() {
 	@autoreleasepool {
-		[NSApplication sharedApplication];
+		[GioApplication sharedApplication];
 		GioAppDelegate *del = [[GioAppDelegate alloc] init];
 		[NSApp setDelegate:del];
 
@@ -438,6 +651,22 @@ void gio_main() {
 
 		globalWindowDel = [[GioWindowDelegate alloc] init];
 
+		// Runs until stopped by applicationDidFinishLaunching.
 		[NSApp run];
 	}
 }
+
+void gio_wakeupMainThread(void) {
+	@autoreleasepool {
+		NSEvent *dummy = [NSEvent otherEventWithType:NSEventTypeApplicationDefined
+		              location:NSZeroPoint
+		         modifierFlags:0
+		             timestamp:0
+		          windowNumber:0
+		               context:nil
+		               subtype:0
+		                 data1:0
+		                 data2:0];
+		[NSApp postEvent:dummy atStart:YES];
+	}
+}

app/os_unix.go

@@ -33,10 +33,6 @@ type WaylandViewEvent struct {
 func (WaylandViewEvent) implementsViewEvent() {}
 func (WaylandViewEvent) ImplementsEvent()     {}
 
-func osMain() {
-	select {}
-}
-
 type windowDriver func(*callbacks, []Option) error
 
 // Instead of creating files with build tags for each combination of wayland +/- x11

app/os_wayland.go

@@ -1222,7 +1222,8 @@ func gio_onKeyboardEnter(data unsafe.Pointer, keyboard *C.struct_wl_keyboard, se
 	w := callbackLoad(unsafe.Pointer(surf)).(*window)
 	s.keyboardFocus = w
 	s.disp.repeat.Stop(0)
-	w.ProcessEvent(key.FocusEvent{Focus: true})
+	w.config.Focused = true
+	w.ProcessEvent(ConfigEvent{Config: w.config})
 }
 
 //export gio_onKeyboardLeave
@@ -1231,7 +1232,8 @@ func gio_onKeyboardLeave(data unsafe.Pointer, keyboard *C.struct_wl_keyboard, se
 	s.serial = serial
 	s.disp.repeat.Stop(0)
 	w := s.keyboardFocus
-	w.ProcessEvent(key.FocusEvent{Focus: false})
+	w.config.Focused = false
+	w.ProcessEvent(ConfigEvent{Config: w.config})
 }
 
 //export gio_onKeyboardKey

app/os_windows.go

@@ -50,7 +50,6 @@ type window struct {
 	placement *windows.WindowPlacement
 
 	animating bool
-	focused   bool
 
 	borderSize image.Point
 	config     Config
@@ -86,10 +85,6 @@ var resources struct {
 	cursor syscall.Handle
 }
 
-func osMain() {
-	select {}
-}
-
 func newWindow(win *callbacks, options []Option) {
 	done := make(chan struct{})
 	go func() {
@@ -269,11 +264,11 @@ func windowProc(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) uintptr
 			Kind: pointer.Cancel,
 		})
 	case windows.WM_SETFOCUS:
-		w.focused = true
+		w.config.Focused = true
-		w.ProcessEvent(key.FocusEvent{Focus: true})
+		w.ProcessEvent(ConfigEvent{Config: w.config})
 	case windows.WM_KILLFOCUS:
-		w.focused = false
+		w.config.Focused = false
-		w.ProcessEvent(key.FocusEvent{Focus: false})
+		w.ProcessEvent(ConfigEvent{Config: w.config})
 	case windows.WM_NCHITTEST:
 		if w.config.Decorated {
 			// Let the system handle it.
@@ -496,7 +491,7 @@ func (w *window) hitTest(x, y int) uintptr {
 }
 
 func (w *window) pointerButton(btn pointer.Buttons, press bool, lParam uintptr, kmods key.Modifiers) {
-	if !w.focused {
+	if !w.config.Focused {
 		windows.SetFocus(w.hwnd)
 	}
 

app/os_x11.go

@@ -657,9 +657,11 @@ func (h *x11EventHandler) handleEvents() bool {
 			// redraw only on the last expose event
 			redraw = (*C.XExposeEvent)(unsafe.Pointer(xev)).count == 0
 		case C.FocusIn:
-			w.ProcessEvent(key.FocusEvent{Focus: true})
+			w.config.Focused = true
+			w.ProcessEvent(ConfigEvent{Config: w.config})
 		case C.FocusOut:
-			w.ProcessEvent(key.FocusEvent{Focus: false})
+			w.config.Focused = false
+			w.ProcessEvent(ConfigEvent{Config: w.config})
 		case C.ConfigureNotify: // window configuration change
 			cevt := (*C.XConfigureEvent)(unsafe.Pointer(xev))
 			if sz := image.Pt(int(cevt.width), int(cevt.height)); sz != w.config.Size {

app/runmain.go

@@ -25,6 +25,6 @@ func runMain() {
 		// Indirect call, since the linker does not know the address of main when
 		// laying down this package.
 		fn := mainMain
-		fn()
+		go fn()
 	})
 }

app/window.go

@@ -630,9 +630,19 @@ func (w *Window) processEvent(e event.Event) bool {
 		}
 		w.coalesced.view = &e2
 	case ConfigEvent:
+		wasFocused := w.decorations.Config.Focused
 		w.decorations.Config = e2.Config
 		e2.Config = w.effectiveConfig()
 		w.coalesced.cfg = &e2
+		if f := w.decorations.Config.Focused; f != wasFocused {
+			w.queue.Queue(key.FocusEvent{Focus: f})
+		}
+		t, handled := w.queue.WakeupTime()
+		if handled {
+			w.setNextFrame(t)
+			w.updateAnimation()
+		}
+		return handled
 	case event.Event:
 		focusDir := key.FocusDirection(-1)
 		if e, ok := e2.(key.Event); ok && e.State == key.Press {
@@ -674,6 +684,13 @@ func (w *Window) processEvent(e event.Event) bool {
 
 // Event blocks until an event is received from the window, such as
 // [FrameEvent], or until [Invalidate] is called.
+//
+// Note: if more than one Window is active, at least one must have
+// its Event called from the main goroutine that runs the main
+// function. This is necessary because some operating system GUI
+// implementations require control of the main thread.
+// For this reason, it is allowed to call Event even after a
+// DestroyEvent has been received.
 func (w *Window) Event() event.Event {
 	w.init()
 	return w.basic.Event()