app: [iOS] add support for buildmode exe

Up until now, the iOS part has relied on a tool such as gogio to
synthesize a main function. This change adds support for running direcetly
in exe mode, while retaining support for embedded Gio in C programs.

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

app/os_ios.go

@@ -12,6 +12,7 @@ package app
 #include <UIKit/UIKit.h>
 #include <stdint.h>
 
+__attribute__ ((visibility ("hidden"))) int gio_applicationMain(int argc, char *argv[]);
 __attribute__ ((visibility ("hidden"))) void gio_viewSetHandle(CFTypeRef viewRef, uintptr_t handle);
 
 struct drawParams {
@@ -81,6 +82,7 @@ import "C"
 import (
 	"image"
 	"io"
+	"os"
 	"runtime"
 	"runtime/cgo"
 	"runtime/debug"
@@ -394,12 +396,47 @@ func newWindow(win *callbacks, options []Option) {
 	<-mainWindow.windows
 }
 
+var mainMode = mainModeUndefined
+
+const (
+	mainModeUndefined = iota
+	mainModeExe
+	mainModeLibrary
+)
+
 func osMain() {
+	if !isMainThread() {
+		panic("app.Main must be run on the main goroutine")
+	}
+	switch mainMode {
+	case mainModeUndefined:
+		mainMode = mainModeExe
+		var argv []*C.char
+		for _, arg := range os.Args {
+			a := C.CString(arg)
+			defer C.free(unsafe.Pointer(a))
+			argv = append(argv, a)
+		}
+		C.gio_applicationMain(C.int(len(argv)), unsafe.SliceData(argv))
+	case mainModeExe:
+		panic("app.Main may be called only once")
+	case mainModeLibrary:
+		// Do nothing, we're embedded as a library.
+	}
 }
 
 //export gio_runMain
 func gio_runMain() {
-	runMain()
+	if !isMainThread() {
+		panic("app.Main must be run on the main goroutine")
+	}
+	switch mainMode {
+	case mainModeUndefined:
+		mainMode = mainModeLibrary
+		runMain()
+	case mainModeExe:
+		// Do nothing, main has already been called.
+	}
 }
 
 func (UIKitViewEvent) implementsViewEvent() {}

app/os_ios.m

@@ -280,3 +280,23 @@ void gio_viewSetHandle(CFTypeRef viewRef, uintptr_t handle) {
 	GioView *v = (__bridge GioView *)viewRef;
 	v.handle = handle;
 }
+
+@interface _gioAppDelegate : UIResponder <UIApplicationDelegate>
+@property (strong, nonatomic) UIWindow *window;
+@end
+
+@implementation _gioAppDelegate
+- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
+	self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
+	GioViewController *controller = [[GioViewController alloc] initWithNibName:nil bundle:nil];
+	self.window.rootViewController = controller;
+	[self.window makeKeyAndVisible];
+	return YES;
+}
+@end
+
+int gio_applicationMain(int argc, char *argv[]) {
+	@autoreleasepool {
+		return UIApplicationMain(argc, argv, nil, NSStringFromClass([_gioAppDelegate class]));
+	}
+}