CALayers.mm

#import <Foundation/Foundation.h>
#import <AppKit/AppKit.h>
#import <QuartzCore/CAMetalLayer.h>

@interface MyAppDelegate : NSObject <NSApplicationDelegate>
{
    NSWindow *window;
}
@end

@implementation MyAppDelegate

-(id) init
{
    self = [super init];
    if (self)
    {
        NSRect mainDisplayRect = [[NSScreen mainScreen] frame];

        NSRect windowRect = NSMakeRect(mainDisplayRect.origin.x + (mainDisplayRect.size.width) * 0.25,
                                     mainDisplayRect.origin.y + (mainDisplayRect.size.height) * 0.25,
                                     mainDisplayRect.size.width * 0.5,
                                     mainDisplayRect.size.height * 0.5);

        NSUInteger windowStyle = NSTitledWindowMask | NSClosableWindowMask | NSMiniaturizableWindowMask;

        NSInteger windowLevel = NSMainMenuWindowLevel + 1;

        window = [[NSWindow alloc] initWithContentRect:windowRect styleMask:windowStyle backing:NSBackingStoreBuffered defer:NO];
        [window setLevel:windowLevel];
        [window setOpaque:YES];
        [window setHasShadow:YES];
        [window setPreferredBackingLocation:NSWindowBackingLocationVideoMemory];
        [window setHidesOnDeactivate:NO];
        [window setBackgroundColor:[NSColor colorWithDeviceRed:200.0 / 255.0 green:10.0 / 255.0 blue:45.0 / 255.0 alpha:1.0f]];

        NSRect topLevelViewRect = NSMakeRect(50, 50, windowRect.size.width - 100, windowRect.size.height - 100);
        NSView* windowNSview = [[NSView alloc] initWithFrame:topLevelViewRect];
        [windowNSview setWantsLayer:YES];
        windowNSview.layer.backgroundColor = [[NSColor colorWithDeviceRed:80.0 / 255.0 green:130.0 / 255.0 blue:245.0 / 255.0 alpha:1.0f] CGColor];
        [window.contentView addSubview:windowNSview];

        NSRect yellowViewRect = NSMakeRect(50, 50, topLevelViewRect.size.width * 0.5 - 50, topLevelViewRect.size.height - 100);
        NSView* view = [[NSView alloc] initWithFrame:yellowViewRect];
        [view setWantsLayer:YES];
        view.layer.backgroundColor = [[NSColor colorWithDeviceRed:248.0 / 255.0 green:207.0 / 255.0 blue:96.0 / 255.0 alpha:1.0f] CGColor];;
        [windowNSview addSubview:view];

        NSRect redViewRect =NSMakeRect(topLevelViewRect.size.width * 0.5, 50, topLevelViewRect.size.width * 0.5 - 50, topLevelViewRect.size.height - 100);
        NSView* metalView = [[NSView alloc] initWithFrame:redViewRect];
        [metalView setWantsLayer:YES];
        [metalView setLayer:[CAMetalLayer layer]];
        metalView.layer.backgroundColor = [[NSColor colorWithDeviceRed:121.0 / 255.0 green:65.0 / 255.0 blue:106.0 / 255.0 alpha:1.0f] CGColor];
        [windowNSview addSubview:metalView];
    }
    return self;
}

- (void)applicationWillFinishLaunching:(NSNotification *)notification{ [window makeKeyAndOrderFront:self]; }
- (void)applicationDidFinishLaunching:(NSNotification*)aNotification{}
- (void)dealloc
{
    [window release];
    [super dealloc];
}
@end


int main(int argc, const char * argv[])
{

    @autoreleasepool
    {
        NSApplication *app = [NSApplication sharedApplication];
        [app setDelegate:[[[MyAppDelegate alloc] init] autorelease]];
        [app run];
    }
    return 0;
}

// Command to build in TERMINAL
/*clang -framework Foundation -framework Cocoa -framework QuartzCore CALayers.mm -o CALayers.app*/