关闭/最小化/全屏居中处理(仿Mac QQ)，效果如下

image-20201106143307906

//  FSWindowCtl.m
@interface FSWindowCtl ()<NSWindowDelegate>

@end

@implementation FSWindowCtl

- (void)windowDidLoad {
    [super windowDidLoad];
    [self settingWindowStyle];
}
// 设置window样式
- (void)settingWindowStyle {
    self.window.titlebarAppearsTransparent = YES;
    self.window.titleVisibility = NSWindowTitleHidden;
    self.window.styleMask = NSWindowStyleMaskClosable | NSWindowStyleMaskResizable | NSWindowStyleMaskTitled | NSWindowStyleMaskMiniaturizable | NSWindowStyleMaskFullSizeContentView;
    [self.window setMovableByWindowBackground:YES];
    [self updateTitleBarOfWindow:false];
}

// 修改关闭、最小化、全屏的位置
- (void)updateTitleBarOfWindow:(BOOL)fullScreen {
    CGFloat kTitlebarH = 54.0;
    CGFloat kFullScreenButtonYOrigin = 3.0;
    NSRect windowFrame = self.window.frame;
    NSView *titlebarContainerView = [self.window standardWindowButton:NSWindowCloseButton].superview.superview;
    NSRect titlebarContainerFrame = titlebarContainerView.frame;
    titlebarContainerFrame.origin.y = windowFrame.size.height - kTitlebarH;
    titlebarContainerFrame.size.height = (CGFloat)kTitlebarH;
    titlebarContainerView.frame = titlebarContainerFrame;
    
    CGFloat buttonX = 12.0;
    NSButton *closeBtn = [self.window standardWindowButton:NSWindowCloseButton];
    NSButton *minimizeBtn = [self.window standardWindowButton:NSWindowMiniaturizeButton];
    NSButton *zoomBtn = [self.window standardWindowButton:NSWindowZoomButton];
    
    for (NSButton *buttonView in @[closeBtn, minimizeBtn, zoomBtn]) {
        NSRect buttonFrame = buttonView.frame;
        buttonFrame.origin.y = fullScreen ? kFullScreenButtonYOrigin : round((kTitlebarH - buttonFrame.size.height)/2.0);
        buttonFrame.origin.x = (CGFloat)buttonX;
        buttonX = buttonFrame.size.width + buttonX + 6;
        [buttonView setFrameOrigin:buttonFrame.origin];
    }
}

#pragma mark - NSWindowDelegate
- (void)windowDidEnterFullScreen:(NSNotification *)notification {
    [self updateTitleBarOfWindow:YES];
}

- (void)windowDidExitFullScreen:(NSNotification *)notification {
    [self updateTitleBarOfWindow:NO];
}

- (void)windowDidResize:(NSNotification *)notification {
    [self updateTitleBarOfWindow:NO];
}

@end

Github Demo