An extension on NSScreen providing menubar dimensions across various system states.

NSScreen+MenuBarHeights.h

//
//  NSScreen+MenuBarHeights.h
//
//
//  Created by Stephan Casas on 6/26/24.
//

@import Foundation;
@import AppKit;

@interface NSScreen (__ScreenMenuBarHeights)

/// A private-API object representing the height of the menu bar in its various states for a particular display.
@property(readonly) id screenMenuBarHeights;

/// The vertical drawing area of the menu bar for this display.
@property(readonly) CGFloat menuBarLayoutHeight;

/// The vertical clearance inset maintained to prevent windows from occluding the menu bar on this display.
@property(readonly) CGFloat menuBarRestingHeight;

@end

NSScreen+MenuBarHeights.m

//
//  NSScreen+MenuBarHeights.m
//  
//
//  Created by Stephan Casas on 6/30/24.
//

@import ObjectiveC;
#import "NSScreen+MenuBarHeights.h"

@implementation NSScreen (__ScreenMenuBarHeights)

/// A private-API object representing the height of the menubar in its various states for a particular display.
- (id)screenMenuBarHeights {
    NSBundle * appKit = [NSBundle bundleWithPath:@"/System/Library/Frameworks/AppKit.framework"];
    [appKit load];
    
    NSNumber * displayID = [self valueForKey:@"_displayID"];
    
    id __NSScreenMenuBarHeights = [[appKit classNamed:@"_NSScreenMenuBarHeights"] alloc];
    return ((id (*)(id, SEL, CGDirectDisplayID))objc_msgSend)(__NSScreenMenuBarHeights, NSSelectorFromString(@"_initWithDisplayID:"), [displayID intValue]);
}

/// The vertical drawing area of the menubar for this display.
- (CGFloat)menuBarLayoutHeight {
    NSNumber * layoutHeight = [[self screenMenuBarHeights] valueForKey:@"layoutHeight"];
    
    return [layoutHeight doubleValue];
}

/// The vertical clearance inset maintained to prevent windows from occluding the menubar on this display.
- (CGFloat)menuBarRestingHeight {
    NSNumber * restingHeight = [[self screenMenuBarHeights] valueForKey:@"restingHeight"];
    
    return [restingHeight doubleValue];
}

@end