float OSXDeviceScaleFactor()
{
    NSArray *ar = [NSApp orderedWindows]; // Get all NSWindow of the Unity player app.
    NSWindow *window = [ar objectAtIndex:0]; // Get the first window. Usually, there would be only one NSWindow in the app startup process unless there is another native plugin doing NSWindow related work. 
    NSScreen *screen = window.screen; // Get the NSScreen where the windows is at
    if (!screen) {
        screen = [NSScreen mainScreen]; // If the screen reference is NULL, get main screen instead.
    }
    if (screen)
    {
        return screen.backingScaleFactor; // Access the backingScaleFactor, this is available on macOS 10.7+. 
    }
    return 1;
}

#import "NSWindow+NSScreenUtils.h"
#import <objc/runtime.h>
#import "UIWidgetsMessageManager.h"

@implementation NSWindow (NSScreenUtils)


// Using method swizzling to inject notification on library load. Notice this bundle should be marked as 'Load on Start' in the Unity inspector panel
+ (void)load {
    NSLog(@"NSWindow + NSScreenUtils Load");
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^
                  {
                      NSString *bundleIdentifier = [[NSBundle mainBundle] bundleIdentifier];
                      if ([bundleIdentifier isEqualToString:@"com.unity3d.UnityEditor5.x"]) {
// if bundle id is Unity, then don't exchange method imp.
                      }
                      else
                      {
// Exchange method implementation to override the init method of NSWindow
                          [UIWidgetsMessageManager getInstance];
                          NSLog(@"NSWindow + NSScreenUtils Enabled for %@",bundleIdentifier);
                          [self exchangeClassMethodMethod:@selector(initWithContentRect:styleMask:backing:defer:) with:@selector(utils_initWithContentRect:styleMask:backing:defer:)];
                          [self exchangeClassMethodMethod:@selector(initWithContentRect:styleMask:backing:defer:screen:) with:@selector(utils_initWithContentRect:styleMask:backing:defer:screen:)];
                      }
                  });
}

+ (void)exchangeClassMethodMethod:(SEL)originalSelector with:(SEL)swizzledSelector
{
    // some magic stuff
}

#pragma mark - Method Swizzling

- (instancetype)utils_initWithContentRect:(NSRect)contentRect styleMask:(NSWindowStyleMask)style backing:(NSBackingStoreType)backingStoreType defer:(BOOL)flag screen:(NSScreen *)screen
{
    NSWindow * instance = [self utils_initWithContentRect:contentRect styleMask:style backing:backingStoreType defer:flag screen:screen];
    if (instance) {
        NSLog(@"utils_initWithContentRect:styleMask:backing:defer:screen:");
// Here we make NSWindow subscribe to a notification when initializing
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onWindowDidChangeBackingProperties:) name:NSWindowDidChangeBackingPropertiesNotification object:nil];
    }
    return instance;
}
- (instancetype)utils_initWithContentRect:(NSRect)contentRect styleMask:(NSWindowStyleMask)style backing:(NSBackingStoreType)backingStoreType defer:(BOOL)flag
{
    NSWindow * instance = [self utils_initWithContentRect:contentRect styleMask:style backing:backingStoreType defer:flag];
// Here we make NSWindow subscribe to a notification when initializing (again, as there are 3 initializer in NSWindow)
    if (instance) {
        NSLog(@"utils_initWithContentRect:styleMask:backing:defer:");
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onWindowDidChangeBackingProperties:) name:NSWindowDidChangeBackingPropertiesNotification object:nil];
    }
    return instance;
}

#pragma mark - Callback
// Send to Unity that ViewportMatricsChanged (Matrics should be Metrics, since ViewportMatricsChanged is used in the current java implementation we would just follow the name)
- (void)onWindowDidChangeBackingProperties:(NSNotification *)notification
{
    NSLog(@"onWindowDidChangeBackingProperties");
    [[UIWidgetsMessageManager getInstance] UIWidgetsMethodMessage:@"ViewportMatricsChanged" :@"UIWidgetViewController.keyboardChanged" :[NSArray array]];
}
@end

// minimal UnitySendMessage clone
static UnityOSXCallback callback = NULL; 
void LinkUnityOSXCallback(UnityOSXCallback externalCallback)
{
    callback = externalCallback;
}
void UnityOSXSendMessage(const char *name,const char *method,const char *arg)
{
    if (callback) {
        callback(name,method,arg);
    }
}