Hotspot in Windows cursor .cur loaded by NSImage?

Question

According to the Cocoa Drawing Guide documentation for Images, NSImage can load a Windows cursor .cur file.

But how do I obtain the hotspot needed for NSCursor - initWithImage:(NSImage *)newImage hotSpot:(NSPoint)point; ?

Answer 1

As the documentation also says,

In OS X v10.4 and later, NSImage supports many additional file formats using the Image I/O framework.

So let's grab a sample cursor file and experiment in a Swift playground:

import Foundation
import ImageIO

let url = Bundle.main.url(forResource: "BUSY_L", withExtension: "CUR")! as CFURL
let source = CGImageSourceCreateWithURL(url, nil)!
print(CGImageSourceCopyPropertiesAtIndex(source, 0, nil)!)

Output:

{
    ColorModel = RGB;
    Depth = 8;
    HasAlpha = 1;
    IsIndexed = 1;
    PixelHeight = 32;
    PixelWidth = 32;
    ProfileName = "sRGB IEC61966-2.1";
    hotspotX = 16;
    hotspotY = 16;
}

So, to get the hotspot safely:

import Foundation
import ImageIO

if let url = Bundle.main.url(forResource: "BUSY_L", withExtension: "CUR") as CFURL?,
    let source = CGImageSourceCreateWithURL(url, nil),
    let properties = CGImageSourceCopyPropertiesAtIndex(source, 0, nil) as? [String: Any],
    let x = properties["hotspotX"] as? CGFloat,
    let y = properties["hotspotY"] as? CGFloat
{
    let hotspot = CGPoint(x: x, y: y)
    print(hotspot)
}

Output:

(16.0, 16.0)