Bug in MetalKit?

metal-bug.m

//
// This appears to be a bug in MTKView.
//
// To reproduce the bug:
//   1. Create a zero-sized window.
//   2. Add MTKView to window.
//   3. Set window size to a non-zero value.
//
// The MTKView never displays its content!
// It's as if the MTKView doesn't even exist.
//
// To avoid this problem, make window non-zero sized
// before adding the MTKView (uncomment line 53).
//
// To compile and run this program:
//     clang metal-bug.m -fobjc-arc -framework Cocoa -framework Metal -framework MetalKit
//     ./a.out
//

#import <Cocoa/Cocoa.h>
#import <MetalKit/MetalKit.h>

@interface MyView: MTKView
@end
@implementation MyView
-(void)drawRect:(NSRect)dirtyRect {
    id<CAMetalDrawable> drawable = [self currentDrawable];
    if (!drawable) {
        return;
    }
    MTLRenderPassDescriptor *pass = [MTLRenderPassDescriptor renderPassDescriptor];
    pass.colorAttachments[0].texture = drawable.texture;
    pass.colorAttachments[0].loadAction = MTLLoadActionClear;
    pass.colorAttachments[0].storeAction = MTLStoreActionStore;
    pass.colorAttachments[0].clearColor = MTLClearColorMake(1, 0, 0, 1);

    id<MTLCommandQueue> queue = [self.device newCommandQueue];
    id<MTLCommandBuffer> buffer = [queue commandBuffer];
    id<MTLRenderCommandEncoder> encoder = [buffer renderCommandEncoderWithDescriptor:pass];
    [encoder endEncoding];
    [buffer presentDrawable:drawable];
    [buffer commit];
}
@end

static void initialize_ui(void) {
    NSRect initial = NSZeroRect;

    //
    // UNCOMMENT THE FOLLOWING LINE TO WORKAROUND THE BUG.
    //

    // initial = NSMakeRect(0, 0, 500, 500);

    NSWindowStyleMask style =
        NSWindowStyleMaskTitled | NSWindowStyleMaskResizable | NSWindowStyleMaskClosable;
    NSWindow *window = [[NSWindow alloc] initWithContentRect:initial
                                                   styleMask:style
                                                     backing:NSBackingStoreBuffered
                                                       defer:YES];
    MyView *view = [[MyView alloc] init];
    view.device = MTLCreateSystemDefaultDevice();
    window.contentView = view;

    [window makeKeyAndOrderFront:nil];

    [window setFrame:NSMakeRect(0, 0, 500, 500) display:YES];
}

@interface AppDelegate: NSObject<NSApplicationDelegate>
@end
@implementation AppDelegate
-(void)applicationDidFinishLaunching:(NSNotification *)notification {
    initialize_ui();
}
@end

int main() {
    @autoreleasepool {
        NSApplication *app = NSApplication.sharedApplication;
        AppDelegate *delegate = [[AppDelegate alloc] init];
        app.delegate = delegate;
        [app run];
    }
    return 0;
}